Contract
No. HY/2011/03
Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road
Section between Scenic Hill and Hong Kong Boundary Crossing Facilities
Quarterly EM&A Report No.
20 (June 2017 to August 2017)
28
December 2017
Revision 0
Main Contractor Designer
Executive Summary
The Hong Kong-Zhuhai-Macao Bridge (HZMB) Hong
Kong Link Road (HKLR) serves to connect the HZMB Main Bridge at the Hong Kong
Special Administrative Region (HKSAR) Boundary and the HZMB Hong Kong Boundary
Crossing Facilities (HKBCF) located at the north eastern waters of the Hong
Kong International Airport (HKIA).
The HKLR project has been separated into two
contracts. They are Contract No.
HY/2011/03 Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road-Section between
Scenic Hill and Hong Kong Boundary Crossing Facilities (hereafter referred to
as the Contract) and Contract No. HY/2011/09 Hong Kong-Zhuhai-Macao Bridge Hong
Kong Link Road-Section between HKSAR Boundary and Scenic Hill.
China State Construction Engineering (Hong Kong)
Ltd. was awarded by Highways Department as the Contractor to undertake the
construction works of Contract No. HY/2011/03. The main works of the Contract
include land tunnel at Scenic Hill, tunnel underneath Airport Road and Airport
Express Line, reclamation and tunnel to the east coast of the Airport Island,
at-grade road connecting to the HKBCF and highway works of the HKBCF within the
Airport Island and in the vicinity of the HKLR reclamation. The Contract is part of the HKLR Project
and HKBCF Project, these projects are considered to be ¡§Designated Projects¡¨,
under Schedule 2 of the Environmental Impact Assessment (EIA) Ordinance (Cap
499) and EIA Reports (Register No. AEIAR-144/2009 and AEIAR-145/2009) were
prepared for the Project. The current
Environmental Permit (EP) EP-352/2009/D for HKLR and EP-353/2009/K for HKBCF
were issued on 22 December 2014 and 11 April 2016, respectively. These
documents are available through the EIA Ordinance Register. The construction
phase of Contract was commenced on 17 October 2012.
BMT Asia Pacific Limited has been appointed by
the Contractor to implement the Environmental Monitoring & Audit (EM&A)
programme for the Contract in accordance with the Updated EM&A Manual for
HKLR (Version 1.0) and will be providing environmental team services to the
Contract.
This is the twentieth Quarterly EM&A report
for the Contract which summarizes the monitoring results and audit findings of
the EM&A programme during the reporting period from 1 June 2017 to 31
August 2017.
Environmental
Monitoring and Audit Progress
The EM&A programme
were undertaken in accordance with the Updated EM&A Manual for HKLR
(Version 1.0). A summary of the
monitoring activities during this reporting period is presented as below:
Monitoring Activity
|
Monitoring Date
|
June 2017
|
July
2017
|
August
2017
|
Air
Quality
|
1-hr
TSP
|
1, 7, 13, 19, 23 and 29
|
3, 7, 13, 19, 25 and 31
|
4, 10, 16, 22 and 28
|
24-hr
TSP at AMS5
|
6, 12, 17, 22 and 29
|
4, 6, 12, 18, 26 and 28
|
3, 9, 15, 21, 26 and 31
|
24-hr
TSP at AMS6
|
6, 12, 17, 22 and 28
|
4, 6, 12, 18, 24 and 28
|
3, 9, 15, 21, 25 and 31
|
Noise
|
1, 7, 15, 19 and 29
|
3, 13, 19, 25 and 31
|
10, 16, 22 and 28
|
Chinese
White Dolphin
|
14, 15, 20 and 26
|
20, 24, 27 and 28
|
7, 15, 21 and 31
|
Mudflat
Monitoring (Ecology)
|
2, 3, 9, 10 and 11
|
--
|
--
|
Mudflat
Monitoring (Sedimentation rate)
|
8
|
--
|
--
|
Site Inspection
|
1, 7, 14, 21 and 30
|
5,
13, 19 and 28
|
2,
9, 16, 24 and 29
|
Due to power
supply failure, the 24-hour TSP monitoring at AMS5 was rescheduled from 28 June
2017 to 29 June 2017.
Due to weather
condition, the noise monitoring schedule was rescheduled from 13 June 2017 to
15 June 2017.
The monitoring
schedule of water quality monitoring for all stations except station CS2 were
adopted from the published Monthly Environmental Monitoring and Audit
(EM&A) Report for June ¡V August 2017 prepared for Contract No. HY/2010/02
Hong Kong-Zhuhai-Macao Bridge Hong Kong Boundary Crossing Facilities ¡V
Reclamation Works. The monitoring schedule of water quality monitoring for
station CS2 was adopted from the published Monthly EM&A Report for June ¡V
August 2017 prepared by Contract No. HY/2011/09 Hong Kong-Zhuhai-Macao Bridge
Hong Kong Link Road ¡V Section between HKSAR Boundary and Scenic Hill.
Due to suitable
weather and ambient temperature, the mudflat monitoring was rescheduled from 12
June 2017 to 2 and 3 June 2017.
Due to weather
condition, the dolphin monitoring schedule was rescheduled from 19 June 2017 to
20 June 2017.
Due to boat
availability, the dolphin monitoring schedule was rescheduled from 21 July 2017
to 20 July 2017, and from 26 July 2017 to 27 July 2017.
Due to motor
failure of high volume sampler, the 24-hour TSP monitoring at Station AMS5 (Ma
Wan Chung Village) was rescheduled from 24 July 2017 to 26 July 2017.
The 24-hour TSP monitoring
at AMS5 was rescheduled from 25 August 2017 to 26 August 2017 due to power
outage of Ma Wan Chung Village caused by seawater engulfment.
A new water quality
monitoring team has been employed for carrying out water quality monitoring
work for the Contract starting from 23 August 2017. The water quality
monitoring on 23 August 2017 was cancelled due to hoisting of typhoon signal
No. 8 or above. No substitute monitoring was conducted due to boat
availability.
Due to a schedule conflict,
the dolphin monitoring was rescheduled from 10 August 2017 to 7 August 2017. Due
to boat availability, the dolphin monitoring was rescheduled from 16 August
2017 to 15 August 2017. Due to weather condition and boat availability, the
dolphin monitoring was rescheduled from 25 August 2017 to 31 August 2017.
Breaches of Action and Limit Levels
A summary of environmental exceedances for this
reporting period is as follows:
Environmental Monitoring
|
Parameters
|
Action Level (AL)
|
Limit Level (LL)
|
Air Quality
|
1-hr TSP
|
0
|
0
|
24-hr TSP
|
0
|
0
|
Noise
|
Leq (30
min)
|
0
|
0
|
Water Quality
|
Suspended
solids level (SS)
|
2
|
0
|
Turbidity
level
|
0
|
0
|
Dissolved
oxygen level (DO)
|
0
|
0
|
Dolphin Monitoring
|
Quarterly
Analysis (Jun 2017 to Aug 2017)
|
0
|
1
|
The Environmental Team investigated all
exceedances and found that they were not project related.
All investigation reports for exceedances of the
Contract have been submitted to ENPO/IEC for comments and/or follow up to
identify whether the exceedances occurred related to other HZMB contracts.
Implementation of Mitigation Measures
Site inspections were carried out on a weekly
basis to monitor the implementation of proper environmental pollution control
and mitigation measures for the Project.
Potential environmental impacts due to the construction activities were
monitored and reviewed.
Complaint Log
There was one complaint received in relation to
the environmental impacts during the reporting period.
A summary of environmental complaints for this
reporting period is as follows:
Environmental Complaint No.
|
Date of Complaint Received
|
Description of Environmental Complaints
|
COM-2016-095(4)
|
15 August 2017
|
Noise nuisances near Dragonair / CNAC (Group)
Building (HKIA)
|
For Environmental Complaint No. COM-2016-095(4),
complaint investigation was undertaken. Based on the investigation result, it
was likely that concerned noise emission was due to the minor rock breaking/
trimming works by the hydraulic breaker. It is considered that the complaint is
likely related to Contract No. HY/2011/03. According to Contractor¡¦s
information, no substantial rock breaking works will be conducted at near CNAC
Tower. Only minor rock breaking/ trimming work may be occasionally conducted at
the concerned work area. The Contractor has been recommended to implement the
measures to minimize the potential noise impact when minor rock breaking/
trimming work.
Notifications of Summons and Prosecutions
There
were no notifications of summons or prosecutions received during this reporting
period.
Reporting Changes
This report has been developed in compliance
with the reporting requirements for the subsequent EM&A reports as required
by the Updated EM&A Manual for HKLR (Version 1.0).
The proposal for the change of Action Level and
Limit Level for suspended solid and turbidity was approved by EPD on 25 March
2013.
The revised Event and Action Plan for dolphin
monitoring was approved by EPD on 6 May 2013.
The original monitoring station at IS(Mf)9
(Coordinate: 813273E, 818850N) was observed inside the perimeter silt curtain
of Contract HY/2010/02 on 1 July 2013, as such the original impact water
quality monitoring location at IS(Mf)9 was temporarily shifted outside the silt
curtain. As advised by the
Contractor of HY/2010/02 in August 2013, the perimeter silt curtain was shifted
to facilitate safe anchorage zone of construction barges/vessels until end of
2013 subject to construction progress.
Therefore, water quality monitoring station IS(Mf)9 was shifted to
813226E and 818708N since 1 July 2013.
According to the water quality monitoring team¡¦s observation on 24 March
2014, the original monitoring location of IS(Mf)9 was no longer enclosed by the
perimeter silt curtain of Contract HY/2010/02. Thus, the impact water quality
monitoring works at the original monitoring location of IS(Mf)9 has been
resumed since 24 March 2014.
Transect lines 1, 2, 7, 8, 9 and 11 for dolphin
monitoring have been revised due to the obstruction of the permanent structures
associated with the construction works of HKLR and the southern viaduct of
TM-CLKL, as well as provision of adequate buffer distance from the Airport
Restricted Areas. The EPD issued a memo and confirmed that they had no
objection on the revised transect lines on 19 August 2015.
Technical issues were observed from impact
water quality monitoring of the Contract and thus published information from
Monthly EM&A Report for June 2017, July 2017 and August 2017 prepared for
Contract No. HY/2010/02 and Contract No. HY/2011/09 were adopted for the
Contract.
A new water quality monitoring team has been
employed for carrying out water quality monitoring work for the Contract
starting from 23 August 2017. Due to marine work of the Expansion of Hong Kong
International Airport into a Three-Runway System (3RS Project), original
locations of water quality monitoring stations CS2, SR5 and IS10 are enclosed
by works boundary of 3RS Project. Alternative impact water quality monitoring stations,
naming as CS2(A), SR5(N) and IS10(N) was approved on 28 July 2017 and were
adopted starting from 23 August 2017 to replace the original locations of water
quality monitoring for the Contract.
1.1.2 The
HKLR project has been separated into two contracts. They are Contract No.
HY/2011/03 Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road-Section between
Scenic Hill and Hong Kong Boundary Crossing Facilities (hereafter referred to
as the Contract) and Contract No. HY/2011/09 Hong Kong-Zhuhai-Macao Bridge Hong
Kong Link Road-Section between HKSAR Boundary and Scenic Hill.
1.1.3 China
State Construction Engineering (Hong Kong) Ltd. was awarded by Highways
Department (HyD) as the Contractor to undertake the construction works of
Contract No. HY/2011/03. The Contract is part of the HKLR Project and
HKBCF Project, these projects are considered to be ¡§Designated Projects¡¨, under
Schedule 2 of the Environmental Impact Assessment (EIA) Ordinance (Cap 499) and
EIA Reports (Register No. AEIAR-144/2009 and AEIAR-145/2009) were prepared for
the Project. The current
Environmental Permit (EP) EP-352/2009/D for HKLR and EP-353/2009/K for HKBCF
were issued on 22 December 2014 and 11 April 2016, respectively. These
documents are available through the EIA Ordinance Register. The construction
phase of Contract was commenced on 17 October 2012. Figure 1.1
shows the project site boundary.
1.1.5 This
is the twentieth Quarterly
Environmental Monitoring and Audit (EM&A) report for the Contract which
summarizes the monitoring results and audit findings of the EM&A programme
during the reporting period from 1 June 2017 to 31 August 2017.
1.2.1
The project organization
structure and lines of communication with respect to the on-site environmental
management structure with the key personnel contact names and numbers are shown
in Appendix A.
1.3
Construction
Programme
1.3.1
A copy of the Contractor¡¦s construction programme is
provided in Appendix B.
1.4
Construction Works Undertaken During
the Reporting Period
1.4.1
A summary of the construction activities undertaken
during this reporting period is shown in Table 1.1. The Works areas of the Contract are
showed in Appendix C.
Table 1.1 Construction
Activities during Reporting Period
Description of Activities
|
Site Area
|
Stockpiling
|
WA7
|
Dismantling/trimming of temporary 40mm
stone platform for construction of seawall
|
Portion X
|
Construction of seawall
|
Portion X
|
Loading and unloading of filling materials
|
Portion X
|
Backfilling at Scenic Hill Tunnel (Cut
& Cover Tunnel)
|
Portion X
|
Excavation for HKBCF to Airport Tunnel
& construction of tunnel box structure
|
Portion X
|
Excavation for diversion of culvert PR14
|
Portion X
|
Works for diversion
|
Airport Road
|
Utilities detection
|
Airport Road/ Airport Express Line/ East Coast Road
|
Establishment of site access
|
Airport Road/ Airport Express Line/ East Coast Road
|
Mined tunnel lining / box jacking
transition zone rebar fixing underneath Airport Road and Airport Express Line
|
Airport Road and Airport Express Line
|
Construction of Tunnel box structure
|
Shaft 3 Extension North Shaft
|
Excavation and lateral support works & Construction
of Tunnel Box Structure for HKBCF to Airport Tunnel West (Cut & Cover
Tunnel)
|
Airport Road
|
Excavation and lateral support works &
construction of tunnel box structure for HKBCF to Airport Tunnel East (Cut
& Cover Tunnel)
|
Portion X
|
Sub-structure, superstructure and finishing
works for Highway Operation and Maintenance Area Building
|
Portion X
|
Superstructure & finishing works for
Scenic Hill Tunnel West Portal Ventilation building
|
West Portal
|
2.1
Summary of
EM&A Requirements
2.1.1
The EM&A programme requires environmental
monitoring of air quality, noise, water quality, dolphin monitoring and mudflat
monitoring as specified in the approved EM&A Manual.
2.1.2
A summary of Impact EM&A requirements is
presented in Table 2.1. The locations of air quality, noise and water quality monitoring
stations are shown as in Figure 2.1. The
transect line layout in Northwest and Northeast Lantau Survey Areas is
presented in Figure 2.2.
Table 2.1 Summary
of Impact EM&A Requirements
Environmental
Monitoring
|
Description
|
Monitoring
Station
|
Frequencies
|
Remarks
|
Air Quality
|
1-hr TSP
|
AMS 5 & AMS
6
|
At least 3 times every 6 days
|
While the
highest dust impact was expected.
|
24-hr TSP
|
At least once every 6 days
|
--
|
Noise
|
Leq (30mins),
L10 (30mins) and
L90 (30mins)
|
NMS 5
|
At least once per week
|
Daytime on normal weekdays
(0700-1900 hrs).
|
Water Quality
|
¡P Depth
¡P Temperature
¡P Salinity
¡P Dissolved Oxygen
(DO)
¡P Suspended Solids
(SS)
¡P DO Saturation
¡P Turbidity
¡P pH
|
¡P Impact Stations:
IS5, IS(Mf)6, IS7, IS8, IS(Mf)9 & IS10,
¡P Control/Far Field
Stations:
CS2 & CS(Mf)5,
¡P Sensitive Receiver
Stations:
SR3, SR4, SR5, SR10A & SR10B
|
Three times per week
during mid-ebb and mid-flood tides (within ¡Ó 1.75 hour of the predicted time)
|
3
(1 m below water surface,
mid-depth and 1 m above sea bed, except where the water depth is less than 6
m, in which case the mid-depth station may be omitted. Should the water depth be less than 3
m, only the mid-depth station will be monitored).
|
Dolphin
|
Line-transect Methods
|
Northeast Lantau survey
area and Northwest Lantau survey area
|
Twice
per month
|
--
|
Mudflat
|
Horseshoe crabs, seagrass beds, intertidal soft shore communities,
sedimentation rates and water quality
|
San Tau and Tung Chung Bay
|
Once every 3 months
|
--
|
2.2.1
Table 2.2 presents
the Action and Limit Levels for the 1-hour TSP, 24-hour TSP and noise level.
Table 2.2 Action
and Limit Levels for 1-hour TSP, 24-hour TSP and Noise
Environmental Monitoring
|
Parameters
|
Monitoring Station
|
Action Level
|
Limit Level
|
Air
Quality
|
1-hr TSP
|
AMS
5
|
352 µg/m3
|
500 µg/m3
|
AMS
6
|
360 µg/m3
|
24-hr TSP
|
AMS
5
|
164 µg/m3
|
260 µg/m3
|
AMS
6
|
173 µg/m3
|
Noise
|
Leq
(30 min)
|
NMS 5
|
When
one documented complaint is received
|
75
dB(A)
|
2.2.2
The Action and Limit
Levels for water quality monitoring are given as in Table 2.3.
Table 2.3 Action
and Limit Levels for Water Quality
Parameter
(unit)
|
Water Depth
|
Action
Level
|
Limit Level
|
Dissolved Oxygen (mg/L)
|
Surface and Middle
|
5.0
|
4.2 except 5 for Fish
Culture Zone
|
Bottom
|
4.7
|
3.6
|
Turbidity (NTU)
|
Depth average
|
27.5 or 120% of upstream
control station¡¦s turbidity at the same tide of the same day;
The action level has been
amended to ¡§27.5 and 120% of upstream control station¡¦s turbidity at the same
tide of the same day¡¨ since 25 March 2013.
|
47.0 or 130% of turbidity
at the upstream control station at the same tide of same day;
The limit level has been
amended to ¡§47.0 and 130% of turbidity at the upstream control station at the
same tide of same day¡¨ since 25 March 2013.
|
Suspended Solid (SS)
(mg/L)
|
Depth average
|
23.5 or 120% of upstream
control station¡¦s SS at the same tide of the same day;
The action level has been
amended to ¡§23.5 and 120% of upstream control station¡¦s SS at the same tide of
the same day¡¨ since 25 March 2013.
|
34.4 or 130% of SS at the
upstream control station at the same tide of same day and 10mg/L for Water
Services Department Seawater Intakes;
The limit level has been
amended to ¡§34.4 and 130% of SS at the upstream control station at the same
tide of same day and 10mg/L for Water Services Department Seawater Intakes¡¨
since 25 March 2013
|
Notes:
(1) Depth-averaged is
calculated by taking the arithmetic means of reading of all three depths.
(2) For DO, non-compliance
of the water quality limit occurs when monitoring result is lower that the
limit.
(3) For SS & turbidity
non-compliance of the water quality limits occur when monitoring result is
higher than the limits.
(4) The change to the
Action and limit Levels for Water Quality Monitoring for the EM&A works was
approved by EPD on 25 March 2013. Therefore, the amended Action and Limit
Levels are applied for the water monitoring results obtained on and after 25
March 2013.
2.2.3
The Action and Limit
Levels for dolphin monitoring are shown in Tables
2.4 and 2.5.
Table 2.4 Action
and Limit Level for Dolphin Impact Monitoring
|
North Lantau
Social Cluster
|
NEL
|
NWL
|
Action Level
|
STG < 70% of baseline
&
ANI < 70% of baseline
|
STG < 70% of baseline
&
ANI < 70% of baseline
|
Limit Level
|
STG < 40% of baseline
&
ANI < 40% of baseline
|
Remarks:
(1)
STG
means quarterly average encounter rate of number of dolphin sightings.
(2)
ANI
means quarterly average encounter rate of total number of dolphins.
(3)
For
North Lantau Social Cluster, AL will be triggered if either NEL or NWL fall
below the criteria; LL will be triggered if both NEL and NWL fall below the
criteria.
Table 2.5 Derived
Value of Action Level (AL) and Limit Level (LL)
|
North Lantau
Social Cluster
|
NEL
|
NWL
|
Action Level
|
STG < 4.2 & ANI
< 15.5
|
STG < 6.9 & ANI
< 31.3
|
Limit Level
|
(STG < 2.4 & ANI
< 8.9) and (STG < 3.9 & ANI < 17.9)
|
Remarks:
(1)
STG
means quarterly average encounter rate of number of dolphin sightings.
(2)
ANI
means quarterly average encounter rate of total number of dolphins.
(3)
For
North Lantau Social Cluster, AL will be triggered if either NEL or NWL fall
below the criteria; LL will be triggered if both NEL and NWL fall below the
criteria.
2.3.1
The Event Actions Plans for air quality, noise,
water quality and dolphin monitoring are annexed in Appendix D.
2.4.1 Environmental mitigation
measures for the contract were recommended in the approved EIA Report. Appendix E lists the recommended
mitigation measures and the implementation status.
3
Environmental
Monitoring and Audit
3.1
Implementation of
Environmental Measures
3.1.1
In response to the site audit findings, the
Contractor have rectified all observations identified in environmental site
inspections undertaken during the reporting period. Details of site audit
findings and the corrective actions during the reporting period are presented
in Appendix F.
3.1.2
A summary of the Implementation Schedule of
Environmental Mitigation Measures (EMIS) is presented in Appendix E.
3.1.3 Regular
marine travel route for marine vessels were implemented properly in accordance
to the submitted plan and relevant records were kept properly.
3.1.4 Dolphin
Watching Plan was implemented during the reporting period.
No dolphins inside the silt curtain were observed. The relevant records were
kept properly.
3.2.1 The
monitoring results for 1-hour TSP and 24-hour TSP are summarized in Tables 3.1 and 3.2
respectively. Detailed impact air quality monitoring results and relevant graphical
plots are presented in Appendix G.
Table 3.1 Summary
of 1-hour TSP Monitoring Results Obtained During the Reporting Period
Reporting Period
|
Monitoring
Station
|
Average (mg/m3)
|
Range (mg/m3)
|
Action Level (mg/m3)
|
Limit Level (mg/m3)
|
June 2017
|
AMS5
|
16
|
8 ¡V 36
|
352
|
500
|
AMS6
|
13
|
4 ¡V 28
|
360
|
July 2017
|
AMS5
|
23
|
3 ¡V 97
|
352
|
AMS6
|
22
|
2 ¡V 93
|
360
|
August 2017
|
AMS5
|
45
|
10 ¡V 200
|
352
|
AMS6
|
38
|
11 ¡V 142
|
360
|
Table 3.2 Summary
of 24-hour TSP Monitoring Results Obtained During the Reporting Period
Reporting Period
|
Monitoring
Station
|
Average (mg/m3)
|
Range (mg/m3)
|
Action Level (mg/m3)
|
Limit Level (mg/m3)
|
June 2017
|
AMS5
|
34
|
30 ¡V 39
|
164
|
260
|
AMS6
|
48
|
23 ¡V 95
|
173
|
July 2017
|
AMS5
|
44
|
28 ¡V 54
|
164
|
AMS6
|
48
|
23 ¡V 118
|
173
|
August 2017
|
AMS5
|
38
|
17 ¡V 60
|
164
|
AMS6
|
55
|
33 ¡V 105
|
173
|
3.2.2
No Action Level and
Limit Level exceedances of 1-hr TSP and 24-hr TSP were recorded at AMS5 and
AMS6 during the reporting period.
3.2.3
Record of notification
of environmental quality limit exceedances are provided in Appendix M.
3.3
Noise Monitoring Results
3.3.1
The monitoring results for construction noise
are summarized in Table 3.3 and the
monitoring results and relevant graphical plots for this reporting
period are provided in Appendix H.
Table 3.3 Summary of Construction Noise
Monitoring Results Obtained During the Reporting Period
Reporting period
|
Monitoring Station
|
Average Leq (30 mins),
dB(A)*
|
Range of Leq (30
mins), dB(A)*
|
Action Level
|
Limit Level Leq (30
mins), dB(A)
|
June 2017
|
NMS5
|
66
|
60 ¡V 70
|
When one documented complaint is received
|
75
|
July 2017
|
58
|
57 ¡V 60
|
August 2017
|
57
|
56 ¡V 57
|
3.3.2
No Action and Limit Level exceedances for noise
were recorded during daytime on normal weekdays of the reporting period.
3.3.3 Major
noise sources during the noise monitoring included construction activities of
the Contract and nearby traffic noise and insect noise.
3.4.1 The
monitoring results of water quality monitoring in the reporting period for all
stations except station CS2 were adopted from the published Monthly EM&A
Report (June 2017, July 2017 and August 2017) for Contract No. HY/2010/02.
3.4.2 The
monitoring results of water quality monitoring in the reporting period for
station CS2 was adopted from the published Monthly EM&A Report (June 2017,
July 2017 and August 2017) for Contract No. HY/2011/09.
3.4.3
For marine water quality monitoring, no Limit
Level exceedances of dissolved oxygen, turbidity and suspended solid levels
were recorded by the ET of Contract
No. HY/2010/02 and Contract No. HY/2011/09 during the reporting period. No
Action Level exceedances of dissolved oxygen and turbidity levels were
recorded by the ET of Contract
No. HY/2010/02 and Contract No. HY/2011/09 during the reporting period. There
were two Action Level exceedances of suspended solid levels were recorded by
the ET of Contract No. HY/2010/02 during the reporting period.
3.4.4
On 12 July 2017, an Action Level exceedance of
suspended solid was recorded at station SR3 during mid-ebb tide. On 14 July
2017, an Action Level exceedance of suspended solid was recorded at station IS7
during mid-flood tide. Removal of surcharge, road and drainage construction at
Zones 1 and 2; seawall construction at Zones 2 and 3; box culvert construction
at Zone 2; and transportation of fill material at Zone 3 were carried out
within the properly deployed silt curtain as recommended in the EIA Report.
There was no marine transportation at Zones 1, 2, and 3. There were no specific
activities recorded during the monitoring period that would cause any
significant impacts on the monitoring results. Also, there was no muddy plume
observed at station IS7 during sampling exercise. No leakage of turbid water or
any abnormity or malpractice for all contract works was observed during the
sampling exercise.
3.4.1 The exceedances of suspended solids
level recorded during reporting period were considered to be attributed to
other external factors such as sea condition, rather than the contract works.
Therefore, the exceedances were considered as non-contract related.
3.4.2 Record of ¡§Notification of Environmental Quality Limit Exceedances¡¨ is
provided in Appendix M.
3.4.3
Water quality impact sources during the water
quality monitoring were the construction activities of the Contract, nearby
construction activities by other parties and nearby operating vessels by other
parties.
Data
Analysis
3.5.1 Distribution Analysis ¡V The
line-transect survey data was integrated with the Geographic Information
System (GIS) in order to visualize and interpret different spatial and temporal
patterns of dolphin distribution using sighting positions. Location data of dolphin groups were
plotted on map layers of Hong Kong using a
desktop GIS (ArcView© 3.1) to examine their distribution patterns in
details. The dataset was also
stratified into different subsets to examine distribution patterns of dolphin
groups with different categories of group sizes, young calves and activities.
3.5.2
Encounter rate analysis ¡V Encounter rates of
Chinese white dolphins (number of on-effort sightings per 100 km of survey
effort, and total number of dolphins sighted on-effort per 100 km of survey
effort) were calculated in NEL and NWL survey areas in relation to the amount
of survey effort conducted during each month of monitoring survey. Dolphin encounter rates were calculated
in two ways for comparisons with the HZMB baseline monitoring results as well
as to AFCD long-term marine mammal monitoring results.
3.5.3
Firstly, for the comparison with the HZMB
baseline monitoring results, the encounter rates were calculated using primary
survey effort alone, and only data collected under Beaufort 3 or below
condition would be used for encounter rate analysis. The average encounter rate of sightings
(STG) and average encounter rate of dolphins (ANI) were deduced based on the
encounter rates from six events during the present quarter (i.e. six sets of
line-transect surveys in North Lantau), which was also compared with the one
deduced from the six events during the baseline period (i.e. six sets of
line-transect surveys in North Lantau).
3.5.4
Secondly, the encounter rates were calculated
using both primary and secondary survey effort collected under Beaufort 3 or
below condition as in AFCD long-term monitoring study. The encounter rate of sightings and
dolphins were deduced by dividing the total number of on-effort sightings (STG)
and total number of dolphins (ANI) by the amount of survey effort for the
present quarterly period.
3.5.5
Quantitative grid analysis on habitat use ¡V To
conduct quantitative grid analysis of habitat use, positions of on-effort
sightings of Chinese White Dolphins collected during the quarterly impact phase
monitoring period were plotted onto 1-km2 grids among NWL and NEL
survey areas on GIS. Sighting
densities (number of on-effort sightings per km2) and dolphin
densities (total number of dolphins from on-effort sightings per km2)
were then calculated for each 1 km by 1 km grid with the aid of GIS. Sighting density grids and dolphin
density grids were then further normalized with the amount of survey effort
conducted within each grid. The total
amount of survey effort spent on each grid was calculated by examining the
survey coverage on each line-transect survey to determine how many times the
grid was surveyed during the study period.
For example, when the survey boat traversed through a specific grid 50
times, 50 units of survey effort were counted for that grid. With the amount of survey effort
calculated for each grid, the sighting density and dolphin density of each grid
were then normalized (i.e. divided by the unit of survey effort).
3.5.6 The
newly-derived unit for sighting density was termed SPSE, representing the
number of on-effort sightings per 100 units of survey effort. In addition, the derived unit for actual
dolphin density was termed DPSE, representing the number of dolphins per 100
units of survey effort. Among the
1-km2 grids that were partially covered by land, the percentage of
sea area was calculated using GIS tools, and their SPSE and DPSE values were
adjusted accordingly. The following
formulae were used to estimate SPSE and DPSE in each 1-km2 grid
within the study area:
SPSE = ((S / E) x 100) /
SA%
DPSE = ((D / E) x 100) /
SA%
where S =
total number of on-effort sightings
D = total number of
dolphins from on-effort sightings
E = total number of units
of survey effort
SA% = percentage of sea
area
3.5.7 Behavioural
analysis ¡V When dolphins were sighted during vessel surveys, their behaviour
was observed. Different activities
were categorized (i.e. feeding, milling/resting, traveling, socializing) and
recorded on sighting datasheets.
This data was then input into a separate database with sighting
information, which can be used to determine the distribution of behavioural
data with a desktop GIS.
Distribution of sightings of dolphins engaged in different activities
and behaviours would then be plotted on GIS and carefully examined to identify
important areas for different activities of the dolphins.
3.5.8 Ranging
pattern analysis ¡V Location data of individual dolphins that occurred during
the 3-month baseline monitoring period were obtained from the dolphin sighting
database and photo-identification catalogue. To deduce home ranges for individual
dolphins using the fixed kernel methods, the program Animal Movement Analyst
Extension, was loaded as an extension with ArcView© 3.1 along with
another extension Spatial Analyst 2.0.
Using the fixed kernel method, the program calculated kernel density
estimates based on all sighting positions, and provided an active interface to
display kernel density plots. The
kernel estimator then calculated and displayed the overall ranging area at 95%
UD level.
Summary
of Survey Effort and Dolphin Sightings
3.5.9
During the period
of June to August 2017, six sets of systematic line-transect vessel surveys
were conducted to cover all transect lines in NWL and NEL survey areas twice
per month.
3.5.10
From these
surveys, a total of 793.06 km of survey effort was collected, with 97.8% of the
total survey effort being conducted under favourable weather conditions (i.e.
Beaufort Sea State 3 or below with good visibility). Among the two areas,
290.58 km and 502.48 km of survey effort were conducted in NEL and NWL survey
areas respectively.
3.5.11
The total survey
effort conducted on primary lines was 575.14 km, while the effort on secondary
lines was 217.92 km. Survey effort conducted on both primary and secondary
lines were considered as on-effort survey data. A summary table of the survey effort is
shown in Annex I of Appendix I.
3.5.12
During the six sets of monitoring surveys in
June to August 2017, 12 groups of 34 Chinese White Dolphins were sighted, with
the summary table of the dolphin sightings shown in Annex II of Appendix I.
All dolphin sightings were made during on-effort search, while eight of
the twelve on-effort dolphin sightings were made on primary lines. In addition, all dolphin groups were
sighted in NWL, and no dolphin was sighted at all in NEL. In fact, since August 2014, only two
sightings of two lone dolphins were made respectively in NEL during HKLR03 monitoring
surveys.
Distribution
3.5.13
Distribution
of dolphin sightings made during monitoring surveys in June to August 2017 is
shown in Figure 1 of Appendix I. The majority of these sightings were
made at the northwest portion of the North Lantau region, mainly around Lung
Kwu Chau, near Castle Peak Power Station and at the mouth of Deep Bay near
Black Point (Figure 1 of Appendix
I). Two dolphin groups were
also sighted at the southwestern corner of NWL survey area, or near the HKLR09
alignment. As consistently recorded
in the previous monitoring quarters, the dolphins were completely absent from
the central and eastern portions of North Lantau waters (Figure 1 of Appendix I).
3.5.14
All
dolphin sightings were located far away from the HKBCF and HKLR03 reclamation
sites as well as along the alignment and Tuen Mun-Chek Lap Kok Link (TMCLKL) (Figure 1 of Appendix I). However, two sightings were made near
the alignment of HKLR09 as mentioned above.
3.5.15 Sighting
distribution of dolphins during the present impact phase monitoring period
(June to August 2017) was drastically different from the one during the
baseline monitoring period (Figure 1 of
Appendix I). In the present
quarter, dolphins have disappeared from the NEL region, which was in stark
contrast to their frequent occurrence around the Brothers Islands, near Shum
Shui Kok and in the vicinity of HKBCF reclamation site during the baseline
period (Figure 1 of Appendix I). The nearly complete abandonment of NEL region
by the dolphins has been consistently recorded in the past 17 quarters of
HKLR03 monitoring, which has resulted in zero to extremely low dolphin
encounter rates in this area.
3.5.16
In NWL
survey area, dolphin occurrence was also significantly different between the
baseline and impact phase periods.
During the present impact monitoring period, dolphins were infrequently
sighted at the northwestern and southwestern ends of the area, which was in
stark contrast with their frequent occurrences throughout the area during the
baseline period (Figure 1 of Appendix I).
3.5.17
Another
comparison in dolphin distribution was made between the five quarterly periods
of summer months in 2013-17 (Figure 2 of
Appendix I). Among the five
summer periods, dolphins were regularly sighted in NWL waters in 2013 and 2014,
but their usage there was dramatically reduced in the three subsequent summer
periods, with the only occurrences mostly concentrated near Lung Kwu Chau or
near Shum Wat (Figure 2 of Appendix I).
Encounter Rate
3.5.18
During the present three-month study period, the
encounter rates of Chinese White Dolphins deduced from the survey effort and
on-effort sighting data from the primary transect lines under favourable
conditions (Beaufort 3 or below) for each set of the surveys in NEL and NWL are
shown in Table 3.4. The average encounter rates deduced from
the six sets of surveys were also compared with the ones deduced from the
baseline monitoring period (September ¡V November 2011) (Table 3.5).
3.5.19 To facilitate the comparison with
the AFCD long-term monitoring results, the encounter rates were also calculated
for the present quarter using both primary and secondary survey effort. The encounter rates of sightings (STG)
and dolphins (ANI) in NWL were 2.3 sightings and 6.2 dolphins per 100 km of
survey effort respectively, while the encounter rates of sightings (STG) and
dolphins (ANI) in NEL were both nil for this quarter.
Table
3.4 Dolphin
Encounter Rates (Sightings Per 100 km of Survey Effort) During Reporting Period
(June to August 2017)
Survey Area
|
Dolphin
Monitoring
|
Encounter rate (STG)
(no. of on-effort dolphin sightings per 100 km of survey effort)
|
Encounter rate (ANI)
(no. of dolphins from all on-effort sightings per 100 km of survey effort)
|
Primary Lines Only
|
Primary Lines Only
|
Northeast Lantau
|
Set 1 (14 & 15 Jun 2017)
|
0.00
|
0.00
|
Set 2 (20 & 26 Jun 2017)
|
0.00
|
0.00
|
Set 3 (20 & 24 Jul
2017)
|
0.00
|
0.00
|
Set 4 (27 & 28 Jul 2017)
|
0.00
|
0.00
|
Set 5 (7
& 15 Aug
2017)
|
0.00
|
0.00
|
Set 6 (21 & 31 Aug 2017)
|
0.00
|
0.00
|
Northwest Lantau
|
Set 1 (14 & 15 Jun 2017)
|
0.00
|
0.00
|
Set 2 (20 & 26 Jun 2017)
|
0.00
|
0.00
|
Set 3 (20 & 24 Jul
2017)
|
1.64
|
14.79
|
Set 4 (27 & 28 Jul 2017)
|
0.00
|
0.00
|
Set 5 (7
& 15 Aug
2017)
|
4.95
|
6.61
|
Set 6 (21 & 31 Aug 2017)
|
6.58
|
18.09
|
Table
3.5 Comparison of average dolphin encounter rates from impact
monitoring period (June to August 2017) and baseline monitoring period
(September ¡V November 2011)
Survey Area
|
Encounter rate (STG)
(no. of on-effort dolphin sightings per 100 km of survey effort)
|
Encounter rate (ANI)
(no. of dolphins from all on-effort sightings per 100 km of survey effort)
|
Reporting Period
|
Baseline Monitoring Period
|
Reporting Period
|
Baseline Monitoring Period
|
Northeast Lantau
|
0.0
|
6.00 ¡Ó 5.05
|
0.0
|
22.19 ¡Ó 26.81
|
Northwest Lantau
|
2.20 ¡Ó
2.88
|
9.85 ¡Ó 5.85
|
6.58 ¡Ó 8.12
|
44.66 ¡Ó 29.85
|
Notes:
1) The encounter rates deduced from the baseline monitoring period have been
recalculated based only on the survey effort and on-effort sighting data made
along the primary transect lines under favourable conditions.
2) ¡Ó denotes the standard deviation of the average
encounter rates.
3.5.20
In NEL,
the average dolphin encounter rates (both STG and ANI) in the present
three-month impact monitoring period were both zero with no on-effort sighting
being made, and such extremely low occurrence of dolphins in NEL have been
consistently recorded in the past 17 quarters of HKLR03 monitoring (Table 3.6). This is a serious concern as the dolphin
occurrence in NEL in the past few years (0.0-1.0 for ER(STG) and 0.0-3.9 for
ER(ANI)) have remained exceptionally low when compared to the baseline period (Table 3.6). Dolphins have been
virtually absent from NEL waters since January 2014, with only three groups of
six dolphins sighted there since then despite consistent and intensive survey
effort being conducted in this survey area.
Table
3.6 Comparison of Average
Dolphin Encounter Rates in Northeast Lantau Survey Area from All Quarters of
Impact Monitoring Period and Baseline Monitoring Period (Sep ¡V Nov 2011)
Monitoring Period
|
Encounter rate (STG)
(no. of on-effort dolphin sightings per 100 km of survey effort)
|
Encounter rate (ANI)
(no. of dolphins from all on-effort sightings per 100 km of survey effort)
|
September-November
2011 (Baseline)
|
6.00 ¡Ó 5.05
|
22.19 ¡Ó 26.81
|
December
2012-February
2013 (Impact)
|
3.14
¡Ó 3.21
|
6.33
¡Ó 8.64
|
March-May 2013
(Impact)
|
0.42
¡Ó 1.03
|
0.42
¡Ó 1.03
|
June-August 2013 (Impact)
|
0.88 ¡Ó 1.36*
|
3.91 ¡Ó 8.36*
|
September-November 2013 (Impact)
|
1.01
¡Ó 1.59
|
3.77
¡Ó 6.49
|
December
2013-February
2014 (Impact)
|
0.45
¡Ó 1.10
|
1.34
¡Ó 3.29
|
March-May 2014
(Impact)
|
0.00
|
0.00
|
June-August 2014 (Impact)
|
0.42 ¡Ó 1.04*
|
1.69 ¡Ó 4.15*
|
September-November 2014
(Impact)
|
0.00
|
0.00
|
December
2014-February
2015 (Impact)
|
0.00
|
0.00
|
March-May 2015
(Impact)
|
0.00
|
0.00
|
June-August 2015 (Impact)
|
0.44 ¡Ó 1.08*
|
0.44 ¡Ó 1.08*
|
September-November 2015
(Impact)
|
0.00
|
0.00
|
December
2015-February
2016 (Impact)
|
0.00
|
0.00
|
March-May 2016
(Impact)
|
0.00
|
0.00
|
June-August 2016 (Impact)
|
0.00*
|
0.00*
|
September-November 2016
(Impact)
|
0.00
|
0.00
|
December
2016-February
2017 (Impact)
|
0.00
|
0.00
|
March-May 2017
(Impact)
|
0.00
|
0.00
|
June-August 2017 (Impact)
|
0.00*
|
0.00*
|
Notes:
1) The encounter rates
deduced from the baseline monitoring period have been recalculated based only
on survey effort and on-effort sighting data made along the primary transect
lines under favourable conditions.
2) ¡Ó denotes the standard
deviation of the average encounter rates.
3) The encounter rates in
summer months were in blue and marked with asterisk.
3.5.21
On the
other hand, the average dolphin encounter rates (STG and ANI) in NWL during the
present impact phase monitoring period (reductions of 77.7% and 85.3%
respectively) were only very small fractions of the ones recorded during the
three-month baseline period, indicating a dramatic decline in dolphin usage of
this survey area as well during the present impact phase period (Table 3.7).
3.5.22
During
the same summer quarters, dolphin encounter rates in NWL during summer 2017 was
similar to the previous two summer periods, but was much lower than the ones in
the summer periods of 2013 and 2014 (Table
3.7). Such temporal trend
should be closely monitored in the upcoming monitoring quarters whether the
dolphin occurrence would continue to increase as the construction activities of
HZMB works have been mostly completed in coming months.
Table 3.7 Comparison of Average Dolphin Encounter Rates in Northwest
Lantau Survey Area from All Quarters of Impact Monitoring Period and Baseline
Monitoring Period (Sep ¡V Nov 2011)
Monitoring Period
|
Encounter rate (STG)
(no. of on-effort dolphin sightings per
100 km of survey effort)
|
Encounter rate (ANI)
(no.
of dolphins from all on-effort sightings per 100 km of survey effort)
|
September-November 2011
(Baseline)
|
9.85 ¡Ó 5.85
|
44.66 ¡Ó 29.85
|
December 2012-February 2013
(Impact)
|
8.36 ¡Ó 5.03
|
35.90 ¡Ó 23.10
|
March-May 2013 (Impact)
|
7.75 ¡Ó 3.96
|
24.23 ¡Ó 18.05
|
June-August 2013 (Impact)
|
6.56 ¡Ó 3.68*
|
27.00 ¡Ó 18.71*
|
September-November
2013 (Impact)
|
8.04 ¡Ó 1.10
|
32.48 ¡Ó 26.51
|
December 2013-February 2014
(Impact)
|
8.21 ¡Ó 2.21
|
32.58 ¡Ó 11.21
|
March-May 2014 (Impact)
|
6.51 ¡Ó 3.34
|
19.14 ¡Ó 7.19
|
June-August 2014 (Impact)
|
4.74 ¡Ó 3.84*
|
17.52 ¡Ó 15.12*
|
September-November 2014
(Impact)
|
5.10
¡Ó 4.40
|
20.52
¡Ó 15.10
|
December 2014-February 2015
(Impact)
|
2.91
¡Ó 2.69
|
11.27
¡Ó 15.19
|
March-May 2015 (Impact)
|
0.47
¡Ó 0.73
|
2.36
¡Ó 4.07
|
June-August 2015 (Impact)
|
2.53 ¡Ó 3.20*
|
9.21 ¡Ó 11.57*
|
September-November 2015
(Impact)
|
3.94
¡Ó 1.57
|
21.05
¡Ó 17.19
|
December 2015-February 2016
(Impact)
|
2.64
¡Ó 1.52
|
10.98
¡Ó 3.81
|
March-May 2016 (Impact)
|
0.98
¡Ó 1.10
|
4.78
¡Ó 6.85
|
June-August 2016 (Impact)
|
1.72 ¡Ó 2.17*
|
7.48 ¡Ó 10.98*
|
September-November 2016
(Impact)
|
2.86
¡Ó 1.98
|
10.89
¡Ó 10.98
|
December 2016-February 2017
(Impact)
|
3.80
¡Ó 3.79
|
14.52
¡Ó 17.21
|
March-May 2017 (Impact)
|
0.93
¡Ó 1.03
|
5.25
¡Ó 9.53
|
June-August 2017 (Impact)
|
2.20 ¡Ó 2.88*
|
6.58 ¡Ó 8.12*
|
Notes:
1) The encounter rates deduced from the
baseline monitoring period have been recalculated based only on survey effort
and on-effort sighting data made along the primary transect lines under
favourable conditions.
2) ¡Ó denotes the standard deviation of the average encounter rates.
3) The
encounter rates in summer months were in blue and marked with asterisk.
3.5.23 As
discussed in Hung (2016), the dramatic decline in dolphin usage of NEL waters
in the past few years (including the declines in abundance, encounter rate and
habitat use in NEL, as well as shifts of individual core areas and ranges away
from NEL waters) was possibly related to the HZMB construction works that were
commenced since 2012. Apparently
such noticeable decline has already extended to NWL waters progressively in the
past few years with no sign of recovery, even though the HZMB-related
construction activities have well past the peak.
3.5.24
A two-way ANOVA with repeated measures and
unequal sample size was conducted to examine whether there were any significant
differences in the average encounter rates between the baseline and impact
monitoring periods. The two
variables that were examined included the two periods (baseline and impact
phases) and two locations (NEL and NWL).
3.5.25
For the
comparison between the baseline period and the present quarter (19th
quarter of the impact phase being assessed), the p-values for the differences
in average dolphin encounter rates of STG and ANI were 0.0044 and 0.0202
respectively. If the alpha value is set at 0.05, significant differences were
detected between the baseline and present quarters in both the average dolphin
encounter rates of STG and ANI.
3.5.26
For the comparison between the baseline period
and the cumulative quarters in impact phase (i.e. the first 19 quarters of the
impact phase being assessed), the p-values for the differences in average
dolphin encounter rates of STG and ANI were 0.000001 and 0.000000
respectively. Even if the alpha
value is set at 0.00001, significant differences were still detected in both the
average dolphin encounter rates of STG and ANI (i.e. between the two periods
and the locations).
3.5.27
As indicated in both dolphin distribution
patterns and encounter rates, dolphin usage has been significantly reduced in
both NEL and NWL survey areas during the present quarterly period, and such low
occurrence of dolphins has also been consistently documented in previous
quarters of the past few years.
3.5.28
The dramatic decline in dolphin usage of North
Lantau region raises serious concern, as the timing of the decline in dolphin
usage in North Lantau waters coincided well with the construction schedule of
the HZMB-related projects (Hung 2016). Apparently there was no sign of recovery
of dolphin usage even though most of the marine works associated with the HZMB
construction have been completed.
Group
Size
3.5.29
Group
size of Chinese White Dolphins ranged from one to nine individuals per group in
North Lantau region during June to August 2017. The average dolphin group sizes
from these three months were compared with the ones deduced from the baseline
period in September to November 2011, as shown in Table 3.8.
Table 3.8 Comparison
of Average Dolphin Group Sizes between Reporting Period (Jun ¡V Aug 2017) and
Baseline Monitoring Period (Sep ¡V Nov 2011)
Survey Area
|
Average
Dolphin Group Size
|
Reporting
Period
|
Baseline
Monitoring Period
|
Overall
|
2.83
¡Ó 2.33 (n = 12)
|
3.72
¡Ó 3.13 (n = 66)
|
Northeast Lantau
|
---
|
3.18 ¡Ó 2.16 (n = 17)
|
Northwest Lantau
|
2.83 ¡Ó 2.33 (n = 12)
|
3.92
¡Ó 3.40 (n = 49)
|
Note:
1) ¡Ó denotes the standard deviation of the average
group size.
3.5.30 The
average dolphin group size in NWL waters during June to August 2017 was lower
than the one recorded during the three-month baseline period, but this could be
partly related to the small sample size of 12 dolphin groups when compared to
the 66 groups sighted during the baseline period (Table 3.8).
3.5.31 Notably,
10 of these 12 dolphin groups were composed of 1-4 individuals only, while the
other two groups were medium in size with five and nine individuals
respectively (Annex II of Appendix I).
3.5.32
Distribution
of the two large dolphin groups (i.e. five individuals or more per group)
during the present quarter is shown in Figure
3 of Appendix I, with comparison to the one in baseline period. Both groups were located near Lung Kwu
Chau (Figure 3 of Appendix I). Such distribution pattern was very
different from the baseline period, when the larger dolphin groups were
frequently sighted and evenly distributed in NWL waters, with a few also
sighted in NEL waters (Figure 3 of
Appendix I).
Habitat Use
3.5.33
From
June to August 2017, the five grids with medium to high dolphin densities were
located to the north and west of Lung Kwu Chau as well as near the Castle Peak
Power Station (Figures 4a and 4b of
Appendix I). All grids near
HKLR03/HKBCF reclamation sites as well as TMCLKL alignment did not record any
presence of dolphins at all during on-effort search in the present quarterly
period (Figures 4a and 4b of Appendix I).
3.5.34 However, it should be emphasized that the amount of
survey effort collected in each grid during the three-month period was fairly
low (6-12 units of survey effort for most grids), and therefore the habitat use
pattern derived from the three-month dataset should be treated with
caution. A more complete picture of
dolphin habitat use pattern should be examined when more survey effort for each
grid will be collected throughout the impact phase monitoring programme.
3.5.35
When
compared with the habitat use patterns during the baseline period, dolphin
usage in NEL and NWL has drastically diminished in both areas during the
present impact monitoring period (Figure
5 of Appendix I). During the
baseline period, many grids between Siu Mo To and Shum Shui Kok in NEL recorded
moderately high to high dolphin densities, which was in stark contrast to the
complete absence of dolphins there during the present impact phase period (Figure 5 of Appendix I).
3.5.36
The density patterns were also very different in
NWL between the baseline and impact phase monitoring periods, with high dolphin
usage throughout the area, especially around Sha Chau, near Black Point, to the
west of the airport, as well as between Pillar Point and airport platform
during the baseline period. In
contrast, only several grids with medium to high dolphin densities were located
near Lung Kwu Chau and Pillar Point during the present impact phase period (Figure 5 of Appendix I).
Mother-calf Pairs
3.5.37
During the present quarterly period, no young calf
was sighted at all among the four groups of dolphins.
Activities and Associations with Fishing Boats
3.5.38 During the three-month study period, none of the 12
dolphin groups was observed to be engaged in feeding, socializing, traveling or
milling/resting activity.
3.5.39
Moreover, none of the
dolphin groups was found to be associated with any operating fishing boat
during the present impact phase period.
Summary Photo-identification works
3.5.40
From June to August
2017, over 2,500 digital photographs of Chinese White Dolphins were taken
during the impact phase monitoring surveys for the photo-identification work.
3.5.41
In
total, 21 individuals sighted 27 times altogether were identified (see summary
table in Annex III of Appendix I and photographs of
identified individuals in Annex IV of
Appendix I). All of these
re-sightings were made in NWL. Six individuals (i.e. CH34, NL46, NL123, NL182,
NL202 and WL05) were re-sighted twice, while the rest were only re-sighted once
during the three-month period (Annex III
of Appendix I).
3.5.42
Notably,
three of these 21 individuals (NL202, NL224 and NL236) were also sighted in
West Lantau waters during the HKLR09 monitoring surveys from June to August
2017, showing their extensive individual movements across different survey
areas.
Individual range use
3.5.43
Ranging patterns of the 21 individuals identified
during the three-month study period were determined by fixed kernel method, and
are shown in Annex V of Appendix I.
3.5.44
All identified dolphins sighted in the present
quarter were utilizing NWL waters only, but have completely avoided NEL waters
where many of them have utilized as their core areas in the past (Annex V of Appendix I). This is in contrary to the extensive
movements between NEL and NWL survey areas observed in the earlier impact
monitoring quarters as well as the baseline period.
3.5.45
On the other hand, three individuals (NL202,
NL224 and NL236) consistently utilized North Lantau waters in the past have
extended their range use to WL during the present quarter. In particular, the re-sighting of NL202
in WL waters was notable, as this individual has been frequently observed in
NWL in the past decade, but its appearance in WL was exceptionally rare (the
last re-sighting of NL202 in WL was recorded in August 2008).
3.5.46
In the upcoming quarters, individual range use
and movements should be continuously monitored to examine whether there has
been any consistent shifts of individual home ranges from North Lantau to West
or Southwest Lantau, as such shift could possibly be related to the
HZMB-related construction works (see Hung 2015, 2016).
Action Level / Limit Level Exceedance
3.5.47
There was one Limit Level
exceedance of dolphin monitoring for the quarterly monitoring data (between
June 2017 ¡V August 2017). According to the contractor¡¦s information, the marine
activities undertaken for HKLR03 during the quarter of June 2017 ¡V August 2017
included removal of surcharge, box culvert construction, road and drainage
construction, seawall construction, and transportation of fill material.
3.5.48
There is no evidence
showing the current LL non-compliance directly related to the construction
works of HKLR03 (where the amounts of working vessels for HKLR03 have been
decreasing), although the generally increased amount of vessel traffic in NEL
during the impact phase has been partly contributed by HKLR03 works since
October 2012. It should also be noted that reclamation work under HKLR03
(adjoining the Airport Island) situates in waters which has rarely been used by
dolphins in the past, and the working vessels under HKLR03 have been travelling
from source to destination in accordance with the Marine Travel Route to
minimize impacts on Chinese White Dolphin (CWD). In addition, the contractor will
implement proactive mitigation measures such as avoiding anchoring at Marine
Department¡¦s designated anchorage site ¡V Sham Shui Kok Anchorage (near Brothers
Island) as far as practicable.
3.5.49
According to Monitoring
of Chinese White Dolphins in Southwest Lantau Waters ¡V Fourth Quarterly Report
(December 2015 to February 2016) which is available on ENPO¡¦s website, with
their primary ranges centered in North and West Lantau waters, some individuals
showed apparent range shifts or extensions to Southwest Lantau waters in
2015-16. For example, three
individual dolphins (NL120, WL46 and WL221) indicated obvious shifts in their
range use from NWL to West Lantau (WL) and Southwest Lantau (SWL) waters.
Moreover, many individuals (e.g. NL212, NL260, WL200, SL55, WL232, WL237 and
WL265) have extended their ranges from WL waters to SWL waters. It remains to be seen whether some of
these individuals have permanently shifted their ranges away from their primary
ranges in North Lantau, or begin to spend more times in SWL waters as part of
their ranges.
3.5.50 ENPO updated that the Hong Kong-Zhuhai-Macao Bridge Authority (HZMBA) for
the Mainland section of Hong Kong-Zhuhai-Macao Bridge (HZMB) has commenced an
interim survey on fisheries resources and CWD in the Mainland waters. ENPO
presented the preliminary findings of the HZMBA interim survey on CWD sighting
and photo-identification works which provide solid evidence that some CWD that
were previously more often sighted in HK waters have expanded their ranges into
the Mainland waters, and some with reduced usage in HK waters. These
preliminary data were mentioned in Monitoring of Chinese White Dolphins in
Southwest Lantau Waters ¡V Fourth Quarterly Report (December 2015 to February
2016) which is available on ENPO¡¦s website.
3.5.51 A two-way ANOVA with repeated measures and unequal sample size was
conducted to examine whether there were any significant differences in the
average encounter rates between the baseline and impact monitoring
periods. The two variables that
were examined included the two periods (baseline and impact phases) and two
locations (NEL and NWL).
3.5.52 For the comparison between the baseline period and the present quarter
(19th quarter of the impact phase being assessed), the p-values for the
differences in average dolphin encounter rates of STG and ANI were 0.0044 and
0.0202 respectively. If the alpha
value is set at 0.05, significant differences were detected between the
baseline and present quarters in both the average dolphin encounter rates of
STG and ANI.
3.5.53 For comparison between the baseline period and the cumulative quarters in
impact phase (i.e. first 19 quarters of the impact phase being assessed), the
p-values for the differences in average dolphin encounter rates of STG and ANI
were 0.000001 and 0.000000 respectively.
Even if the alpha value is set at 0.00001, significant differences were
still detected in both the average dolphin encounter rates of STG and ANI (i.e.
between the two periods and the locations).
3.5.54
The AFCD monitoring data
during June 2017 to August 2017 has been reviewed by the dolphin
specialist. During the same
quarter, no dolphin was sighted from 169.50 km of survey effort on primary
lines in NEL, while five groups of 24 dolphins were sighted from 231.50 km of
survey effort on primary lines in NWL. This review has confirmed that the low
occurrence of dolphins reported by the HKLR03 monitoring surveys in summer 2017
in NEL and NWL survey area is accurate.
3.5.55
All dolphin protective
measures are fully and properly implemented in accordance with the EM&A
Manual. According to the Marine Travel Route Plan, the travelling speed of
vessels must not exceed 5 knots when crossing the edge of the proposed marine
park. The Contractor will continue to provide training for skippers to ensure
that their working vessels travel from source to destination to minimize
impacts on Chinese White Dolphin and avoid anchoring at Marine Department¡¦s
designated anchorage site - Sham Shui Kok Anchorage (near Brothers Island) as
far as practicable. Also, it is recommended to complete the marine works of the
Contract as soon as possible so as to reduce the overall duration of impacts
and allow the dolphins population to recover as early as possible.
3.5.56
A meeting was held on 9
October 2017 with attendance of representative of ENPO, Resident Site Staff
(RSS), Environmental Team (ET) and dolphin specialist for Contract Nos.
HY/2010/02, HY/2011/03, HY2011/09, HY/2012/07 and HY/2012/08. The
discussion/recommendation as recorded in the minutes of the meeting, which
might be relevant to HKLR03 Contract are summarized below.
3.5.57
It was concluded that the
HZMB works is one of the contributing factors affecting the dolphins. It was
also concluded the contribution of impacts due to the HZMB works as a whole (or
individual marine contracts) cannot be quantified nor separate from the other
stress factors.
3.5.58
The dolphin specialists
of the projects confirmed that the CWD sighting around the North of Sha Chau
and Lung Kwu Chau Marine Park (SCLKCMP) has significantly decreased, and it was
likely related to the re-routing of high speed ferry (HSF) from Skypier.
3.5.59
It was reminded that the
ETs shall keep reviewing the implementation status of the dolphin related
mitigation measures and remind the contractor to ensure the relevant measures
were fully implemented.
3.5.60
It was recommended that
the marine works of HZMB projects should be completed as soon as possible so as
to reduce the overall duration of impacts and allow the dolphins population to
recover as early as possible.
3.5.61
It was also recommended
that the marine works footprint (e.g., reduce the size of peripheral silt
curtain) and vessels for the marine works should be reduced as much as
possible, and vessels idling / mooring in other part of the North
Lantau shall be avoided whenever possible.
3.5.62
HyD updated that the
draft map of the proposed Brothers Marine Park (BMP) was gazetted in February
2016. ENPO updated that the BMP was approved by the Chief Executive in the
Executive Council in August 2016. The ETs were reminded to update the BMP
boundary in the Regular Marine Travel Route (RMTR) Plan. The BMP was designated
on 30 December 2016.
It was suggested that the protection measures (e.g. speed limit control) for
the approved BMP shall be brought forward so as to provide a better habitat for
dolphin recovery. It was noted that under the latest RMTR Plan, the contractors
have committed to reduce the vessel speed in BMP.
3.5.63
The marine travel route
will shift along the edge of Brother Marine Park as much as practical under the
RMTR Plan. It was noted that even though marine vessels may moor within the
mooring site of BMP, commercial activities including loading / unloading /
transshipment are not allowed except a permit is obtained. The HZMB works
vessels were recommended to avoid the BMP.
3.5.64
It was remined that
starting from January 2016, HSF from the SkyPier will be re-routed north to the
northern edged of the Sha Chau and Lung Kwu Chau Marine Park which currently
has the highest density of CWD in the NWL. While the HSF will reduce speed to
15 knots, the associated disturbance may still affect CWD in the area. It was
implied that the CWDs in the area shall be closely followed.
3.5.65
There was a discussion on
exploring possible further mitigation measures, for example, controlling the
underwater noise. It was noted that the EIA reports for the projects suggested
several mitigation measures, all of which have been implemented.
3.6
Mudflat Monitoring Results
Sedimentation
Rate Monitoring
3.6.1
The baseline sedimentation rate monitoring was
in September 2012 and impact sedimentation rate monitoring was undertaken on 8 June 2017. The mudflat surface levels at the four established
monitoring stations and the corresponding XYZ HK1980 GRID coordinates are
presented in Table 3.9 and Table 3.10.
Table 3.9 Measured
Mudflat Surface Level Results
|
Baseline Monitoring
(September 2012)
|
Impact Monitoring
(June 2017)
|
Monitoring Station
|
Easting
(m)
|
Northing (m)
|
Surface Level
(mPD)
|
Easting
(m)
|
Northing (m)
|
Surface Level
(mPD)
|
S1
|
810291.160
|
816678.727
|
0.950
|
810291.155
|
816678.715
|
1.078
|
S2
|
810958.272
|
815831.531
|
0.864
|
810958.328
|
815831.484
|
0.990
|
S3
|
810716.585
|
815953.308
|
1.341
|
810716.604
|
815953.296
|
1.447
|
S4
|
811221.433
|
816151.381
|
0.931
|
811221.440
|
816151.355
|
1.116
|
Table 3.10 Comparison
of Measurement
|
Comparison of
measurement
|
Remarks and Recommendation
|
Monitoring Station
|
Easting
(m)
|
Northing (m)
|
Surface Level
(mPD)
|
S1
|
-0.005
|
-0.012
|
0.128
|
Level continuously increased
|
S2
|
0.056
|
-0.047
|
0.126
|
Level continuously increased
|
S3
|
0.019
|
-0.012
|
0.106
|
Level continuously increased
|
S4
|
0.007
|
-0.026
|
0.185
|
Level continuously increased
|
3.6.2
This
measurement result was generally and relatively higher than the baseline
measurement at S1, S2,
S3 and S4. The mudflat level is continuously increased.
Water
Quality Monitoring
3.6.3
The mudflat monitoring covered water quality
monitoring data. Reference was made
to the water quality monitoring data of the representative water quality
monitoring station (i.e. SR3) as in the EM&A Manual. The water quality monitoring location
(SR3) is shown in Figure 2.1.
3.6.4 Impact
water quality monitoring in San Tau (monitoring station SR3) was conducted in
June 2017. The monitoring parameters included dissolved oxygen (DO), turbidity
and suspended solids (SS).
3.6.5 The Impact monitoring result for SR3 in June 2017 were adopted from the
published Monthly EM&A Report for Contract No. HY/2010/02.
Mudflat Ecology Monitoring
Sampling
Zone
3.6.6 In order to collect baseline information of
mudflats in the study site, the study site was divided into three sampling
zones (labeled as TC1, TC2, TC3) in Tung Chung Bay and one zone in San Tau
(labeled as ST) (Figure 2.1 of Appendix N). The horizontal shoreline of sampling
zones TC1, TC2, TC3 and ST were about 250 m, 300 m, 300 m and 250 m
respectively (Figure 2.2 of Appendix N).
Survey of horseshoe crabs, seagrass beds and intertidal communities were
conducted in every sampling zone. The present survey was conducted in June 2017
(totally 5 sampling days between 2nd and 11th June 2017).
3.6.7 Since the field survey of Jun. 2016,
increasing number of trashes and even big trashes (Figure 2.3 of Appendix N) were found in every sampling zone. It
raised a concern about the solid waste dumping and current-driven waste issues
in Tung Chung Wan. Respective measures (e.g. manual clean-up) should be
implemented by responsible units.
Horseshoe
Crabs
3.6.8
Active search method was conducted for horseshoe
crab monitoring by two experienced surveyors in every sampling zone. During the
search period, any accessible and potential area would be investigated for any
horseshoe crab individuals within 2-3 hours of low tide period (tidal level
below 1.2 m above Chart Datum (C.D.)). Once a horseshoe crab individual was
found, the species was identified referencing to Li (2008). The prosomal width,
inhabiting substratum and respective GPS coordinate were recorded. A
photographic record was taken for future investigation. Any grouping behavior
of individuals, if found, was recorded. The horseshoe crab surveys were
conducted on 2nd (for TC1), 3rd (for TC2) and 9th
(for TC3 and ST) June 2017. The weather was generally hot on all field days without
rainfall.
3.6.9
In present survey (Jun. 2017), a big horseshoe crab
was tangled by a trash gill net in ST mudflat (Figure 2.3 of Appendix N). It was released to sea once after photo
recording. The horseshoe crab of such size should be inhabitating sub-tidal
environment while it forages on intertidal shore occasionally during high tide
period. If it is tangled by the trash net for few days, it may die due to
starvation or overheat during low tide period. These trash gill nets are
definitely ¡¥fatal trap¡¦ for the horseshoe crabs and other marine life. Manual
clean-up should be implemented as soon as possible by responsible units.
Seagrass Beds
3.6.10 Active search
method was conducted for seagrass bed monitoring by two experienced surveyors
in every sampling zone. During the search period, any accessible and potential
area would be investigated for any seagrass beds within 2-3 hours of low tide
period. Once seagrass bed was found, the species, estimated area, estimated
coverage percentage and respective GPS coordinates were recorded. The seagrass
beds surveys were conducted on 2nd (for TC1), 3rd (for
TC2) and 9th (for TC3 and ST) June 2017. The weather was generally
hot on all field days without rainfall.
Intertidal Soft Shore
Communities
3.6.11 The intertidal
soft shore community surveys were conducted in low tide period on 2nd
(for TC1), 3rd (for TC2), 10th (for TC3) and 11th
(for ST) June 2017. In every sampling zone, three 100m horizontal transect
lines were laid at high tidal level (H: 2.0 m above C.D.), mid tidal level (M:
1.5 m above C.D.) and low tidal level (L: 1.0 m above C.D.). Along every
horizontal transect line, ten random quadrats (0.5 m x 0.5 m) were placed.
3.6.12
Inside a quadrat, any visible epifauna were
collected and were in-situ identified
to the lowest practical taxonomical resolution. Whenever possible a hand core
sample (10 cm internal diameter 20 cm depth) of sediments was collected in the
quadrat. The core sample was gently washed through a sieve of mesh size 2.0 mm in-situ. Any visible infauna were
collected and identified. Finally the top 5 cm surface sediments was dug for
visible infauna in the quadrat regardless of hand core sample was taken.
3.6.13
All
collected fauna were released after recording except some tiny individuals that
are too small to be identified on site. These tiny individuals were taken to
laboratory for identification under dissecting microscope.
3.6.14
The taxonomic classification was conducted in
accordance to the following references: Polychaetes: Fauchald (1977), Yang and
Sun (1988); Arthropods: Dai and Yang (1991), Dong (1991); Mollusks: Chan and
Caley (2003), Qi (2004).
Data
Analysis
3.6.15 Data
collected from direct search and core sampling was pooled in every quadrat for
data analysis. Shannon-Weaver Diversity Index (H¡¦) and Pielou¡¦s Species
Evenness (J) were calculated for every quadrat using the formulae below,
H¡¦= -£U ( Ni / N ) ln ( Ni / N ) (Shannon and Weaver,
1963)
J = H¡¦ / ln
S, (Pielou, 1966)
where S is the total number of species in the sample,
N is the total number of individuals, and Ni is the number of individuals of
the ith species.
Mudflat
Ecology Monitoring Results and Conclusion
Horseshoe
Crabs
3.6.16 In the present survey, two species of horseshoe
crab Carcinoscorpius rotundicauda
(total 133 ind.) and Tachypleus
tridentatus (total 125 ind.) were recorded. For one sight record, grouping
of 2-20 individuals was observed at same locations with similar substratum
(fine sand or soft mud, slightly submerged). Photo records were shown in Figure 3.1 of Appendix N while the complete survey records were listed in Annex II of Appendix N. Besides, one
tiny individual (prosomal width ~8 mm) was found in TC3 but identification to
species was not possible. Hence this record was excluded from the data
analysis.
3.6.17 Table
3.1 of Appendix N summarizes the survey results of horseshoe
crab in the present survey. For Carcinoscorpius
rotundicauda, moderate number of individuals (22 ind.) were found in TC1
that search record was at low-moderate level (5.5 ind. hr-1 person-1).
The average body size was 46.69 mm (prosomal width ranged 15.72-72.49 mm) in
TC1. More individuals were found in TC3 (57 ind.) and ST (54 ind.) resulting in
relatively higher search records (9.0-9.5 ind. hr-1 person-1).
Smaller individuals were found in TC3 that the average body size was 38.95 mm
(prosomal width ranged 14.29-86.73 mm). The average body size was 53.94 mm
(prosomal width ranged 38.83-83.33 mm) in ST. No individual was found in TC2
regardless of a mating pair (to be discussed below).
3.6.18 For Tachypleus tridentatus, there were only
1-2 individuals in TC1 and TC2 (prosomal width ranged 36.33-67.42 mm). The
search record was very low (0.3-0.5 ind. hr-1 person-1).
Similarly, more individuals were found in TC3 (70 ind.) and ST (52 ind.)
respectively. In TC3, the search record was relatlively higher (11.7 ind. hr-1
person-1) while the average body size was 54.24 mm (prosomal width
ranged 27.57-93.44 mm). In ST, the search record was 8.7 ind. hr-1
person-1 while the average body size was 53.74 mm (prosomal width
ranged 40.41-76.37 mm).
3.6.19
In the previous survey of Mar. 2015, there was one
important finding that a mating pair of Carcinoscorpius
rotundicauda was found in ST (prosomal width: male 155.1 mm, female 138.2
mm) (Figure 3.2 of Appendix N). It
indicated the importance of ST as a breeding ground of horseshoe crab. In the
present survey (Jun. 2017), mating pairs of Carcinoscorpius
rotundicauda were also found in TC2 (prosomal width: male 175.27 mm, female
143.51 mm) and TC3 (prosomal width: male 182.08 mm, female 145.63 mm) (Figure 3.2 of Appendix N). It indicated
that breeding of horseshoe crab could occur along the coast of Tung Chung Wan
rather than ST only, as long as suitable substratum was available. The mating
pairs were found nearly burrowing in soft mud at low tidal level (0.5-1.0 m
above C.D.). The smaller male was holding the opisthosoma (abdomen carapace) of
larger female from behind.
3.6.20
In the
present survey (Jun. 2017), one large individual of Carcinoscorpius rotundicauda (prosomal width 178.67 mm) was tangled
by a trash gill net in ST (Figure 3.3 of
Appendix
N).
Based on the sizes of these mating pairs and tangled individuals, it indicated
that individuals of prosomal width larger than 100 mm would progress its
nursery stage from intertidal habitat to sub-tidal habitat of Tung Chung Wan.
These large individuals might move onto intertidal shore occasionally during
high tide for foraging and breeding.
3.6.21
Because the large individuals (prosomal width >
100 mm) should be inhabiting sub-tidal habitat in most of the time. The records
of mating pair and large, tangled individuals were excluded from the data
analysis to avoid mixing up with juvenile population living on intertidal
habitat. In the previous survey of Jun. 2016, the records of two large
individuals of Carcinoscorpius
rotundicauda (prosomal width 117.37 mm and 178.17 mm) in TC1 were excluded
from data analysis according to the same principle.
3.6.22 No marked individual of horseshoe crab was recorded
in the present survey. Some marked individuals were found in the previous
surveys of Sep. 2013, Mar. 2014 and Sep. 2014. All of them were released through
a conservation programme conducted by Prof. Paul Shin (Department of Biology
and Chemistry, The City University of Hong Kong (CityU)). It was a
re-introduction trial of artificial bred horseshoe crab juvenile at selected
sites. So, that the horseshoe crabs population might be restored in the natural
habitat. Through a personal conversation with Prof. Shin, about 100 individuals
were released in the sampling zone ST on 20 June 2013. All of them were marked
with color tape and internal chip detected by specific chip sensor. There
should be second round of release between June and September 2014 since new
marked individuals were found in the survey of Sep. 2014.
3.6.23 The artificial bred individuals, if found, would be
excluded from the results of present monitoring programme in order to reflect
the changes of natural population. However, the mark on their prosoma might
have been detached during moulting after a certain period of release. The
artificially released individuals were no longer distinguishable from the
natural population without the specific chip sensor. The survey data collected
would possibly cover both natural population and artificially bred individuals.
Population difference among
the sampling zones
3.6.24
Figures 3.4 and
3.5 of Appendix N show the changes
of number of individuals, mean prosomal width and search record of horseshoe
crabs Carcinoscorpius rotundicauda
and Tachypleus tridentatus
respectively in every sampling zone throughout the monitoring period.
3.6.25
For TC3
and ST, medium to high search records (i.e. number of individuals) of both
species were always found in wet season (Jun. and Sep.). The search record of
ST was higher from Sep. 2012 to Jun. 2014 while it was replaced by TC3 from Sep.
2014 to Jun. 2015. The search records were similar between two sampling zones
from Sep. 2015 to Jun. 2016. In Sep. 2016, the search record of Carcinoscorpius rotundicauda in ST was
much higher than TC3. From Mar. to Jun. 2017 (present survey), the search
records of both species were similar again between two sampling zones and
increased with warmer climate. It showed a natural variation of horseshoe crab
population in these two zones due to weather condition and tidal effect during
the survey. No obvious difference of horseshoe crab population was noted
between TC3 and ST.
3.6.26
For
TC1, the search record was at low to medium level throughout the monitoring
period. The change of Carcinoscorpius
rotundicauda was relatively more variable than that of Tachypleus tridentatus. Relatively, the search record was very low
in TC2 (2 ind. in Sep. 2013; 1 ind. in Mar., Jun., Sep. 2014, Mar. and Jun.
2015; 4 ind. in Sep. 2015; 6 ind. in Jun. 2016; 1 ind. in Sep. 2016, Mar. and
Jun. 2017).
3.6.27
About the body size, larger individuals of Carcinoscorpius rotundicauda were
usually found in ST and TC1 relative to those in TC3. For Tachypleus tridentatus, larger individuals were usually found in ST
followed by TC3 and TC1.
3.6.28
Throughout
the monitoring period, it was obvious that TC3 and ST (western shore of Tung
Chung Wan) was an important nursery ground for horseshoe crab especially newly
hatched individuals due to larger area of suitable substratum (fine sand or
soft mud) and less human disturbance (far from urban district). Relatively, other
sampling zones were not a suitable nursery ground especially TC2. Possible
factors were less area of suitable substratum (especially TC1) and higher human
disturbance (TC1 and TC2: close to urban district and easily accessible). In
TC2, large daily salinity fluctuation was a possible factor either since it was
flushed by two rivers under tidal inundation. The individuals inhabiting TC1
and TC2 were confined in small foraging area due to limited area of suitable
substrata. Although a mating pair of Carcinoscorpius
rotundicauda was found in TC2, the hatching rate and survival rate of newly
hatched individuals were believed very low.
Seasonal variation of horseshoe crab
population
3.6.29 Throughout the
monitoring period, the search record of horseshoe crab declined obviously
during dry season especially December (Figures
3.3 and 3.4 of Appendix N). In Dec. 2012, 4 individuals of Carcinoscorpius rotundicauda and 12
individuals of Tachypleus tridentatus
were found only. In Dec. 2013, no individual of horseshoe crab was found. In
Dec. 2014, 2 individuals of Carcinoscorpius
rotundicauda and 8 individuals of Tachypleus
tridentatus were found only. In Dec. 2015, 2 individuals of Carcinoscorpius rotundicauda, 6
individuals of Tachypleus tridentatus
and one newly hatched, unidentified individual were found only. The horseshoe
crabs were inactive and burrowed in the sediments during cold weather (<15
ºC). Similar results of low search record in dry season were reported in a
previous territory-wide survey of horseshoe crab. For example, the search
records in Tung Chung Wan were 0.17 ind. hr-1 person-1
and 0.00 ind. hr-1 person-1 in wet season and dry season
respectively (details see Li, 2008). Relatively the search records were much
higher in Dec. 2016. There were totally 70 individuals of Carcinoscorpius rotundicauda and 24 individuals of Tachypleus tridentatus in TC3 and ST.
Because the survey was arranged in early December while the weather was warm
with sunlight (~22 ºC during dawn according to Hong Kong Observatory database,
Chek Lap Kok station on 5 Dec). In contrast, there was no search record in TC1
and TC2 because the survey was conducted in mid-December with colder and cloudy
weather (~20 ºC during dawn on 19 Dec). The horseshoe crab activity would
decrease gradually with the colder climate.
3.6.30 From Sep. 2012 to
Dec. 2013, Carcinoscorpius rotundicauda
was a less common species relative to Tachypleus
tridentatus. Only 4 individuals were ever recorded in ST in Dec. 2012. This
species had ever been believed of very low density in ST hence the encounter
rate was very low. Since Mar. 2014, it was found in all sampling zones with
higher abundance in ST. Based on its average size (mean prosomal width
39.28-49.81 mm), it indicated that breeding and spawning of this species had
occurred about 3 years ago, along the coastline of Tung Chun Wan. However,
these individuals were still small while their walking trails were
inconspicuous. Hence there was no search record in previous sampling months.
Since Mar. 2014, more individuals were recorded due to larger size and higher
activity (i.e. more conspicuous walking trail).
3.6.31
For Tachypleus
tridentatus, sharp increase of number of individuals was recorded in ST
during the wet season of 2013 (from Mar. to Sep.). According to a personal
conversation with Prof. Shin (CityU), his monitoring team had recorded similar
increase of horseshoe crab population during wet season. It was believed that
the suitable ambient temperature increased its conspicuousness. However similar
pattern was not recorded in the following wet seasons. The number of
individuals increased in Mar. and Jun. 2014 followed by a rapid decline in Sep.
2014. Then the number of individuals fluctuated slightly in TC3 and ST until
Mar. 2017. Apart from natural mortality, migration from nursery soft shore to
subtidal habitat was another possible cause. Since the mean prosomal width of Tachypleus
tridentatus continued to grow and reached about 50 mm since Mar. 2014. Then
it varied slightly between 35-65 mm from Sep. 2014 to Mar. 2017. Most of the
individuals might have reached a suitable size (e.g. prosomal width 50-60 mm)
strong enough to forage in sub-tidal habitat. In the present survey (Jun.
2017), the number of individuals increased sharply again in TC3 and ST.
Although mating pair of Tachypleus tridentatus was not found in previous
surveys, there should be new round of spawning in the wet season of 2016. The
individuals might have grown to a more conspicuous size in 2017 accounting for
higher search record.
3.6.32 Recently, Carcinoscorpius rotundicauda was a more
common horseshoe crab species in Tung Chung Wan. It was recorded in the four
sampling zones while the majority located in TC3 and ST. Due to potential
breeding last year, Tachypleus
tridentatus became common again and distributed in TC3 and ST only. Since
TC3 and ST were regarded as important nursery ground for both horseshoe crab
species, box plots of prosomal width of two horseshoe crab species were
constructed to investigate the changes of population in details.
Box
plot of horseshoe crab populations in TC3
3.6.33
Figure 3.6 of Appendix N shows the
changes of prosomal width of Carcinoscorpius rotundicauda and Tachypleus
tridentatus in TC3. As mentioned above, Carcinoscorpius rotundicauda
was rarely found between Sep. 2012 and Dec. 2013 hence the data were lacking.
In Mar 2014, the major size (50% of individual records between upper (top of
box) and lower quartile (bottom of box)) ranged 40-60 mm while only few
individuals were found. From Mar. 2014 to Mar. 2017, the median prosomal width
(middle line of box) and major size (box) decreased after Mar. of every year.
It was due to more small individuals found. It indicated new rounds of
spawning. Also, there were slight increasing trends of body size from Jun. to
Mar. of next year since 2015. It indicated a stable growth of individuals.
Focused on larger juveniles (circle dots above the box), the size range was
quite variable (prosomal width 60-90 mm) along the sampling months. Juveniles
reaching this size might gradually migrate to sub-tidal habitats.
3.6.34
For Tachypleus
tridentatus, the major size ranged 20-50 mm while the number of individuals
fluctuated from Sep. 2012 to Jun. 2014. Then a slight but consistent growing
trend was observed from Sep. 2014 to Jun. 2015. The prosomal width increased
from 25-35 mm to 35-65 mm. As mentioned, the large individuals might have
reached a suitable size for migrating from the nursery soft shore to subtidal
habitat. It accounted for the declined population in TC3. From Mar. to Sep.
2016, slight increasing trend of major size was noticed again. From Dec. 2016
to Jun. 2017 (present survey), similar increasing trend of major size was noted
with much higher number of individuals. It reflected new round of spawning.
Across the whole monitoring period, the larger juveniles (circle dots above the
box) reached 60-80 mm in prosomal width while it could reach 90 mm in present
survey. Juveniles reaching this size might gradually migrate to sub-tidal
habitats.
Box plot of horseshoe crab populations in ST
3.6.35
Figure 3.7 of Appendix N shows the
changes of prosomal width of Carcinoscorpius rotundicauda and Tachypleus
tridentatus in ST. As mentioned above, Carcinoscorpius rotundicauda
was rarely found between Sep. 2012 and Dec. 2013 hence the data were lacking.
From Mar. 2014 to Sep. 2016, the size of major population decreased and more
small individuals (i.e. circle dots below the box) were recorded after Jun. of
every year. It indicated new round of spawning. Also, there were similar
increasing trends of body size from Sep. to Jun. of next year between 2014 and
2017. It indicated a stable growth of individuals. Across the whole monitoring
period, the larger juveniles (i.e. circle dots above the box) usually ranged
70-80 mm in prosomal width except one individual (prosomal width 107.04 mm)
found in Mar. 2017. It reflected juveniles reaching this size would gradually
migrate to sub-tidal habitats.
3.6.36
For Tachypleus tridentatus, a consistent
growing trend was observed for the major population from Dec. 2012 to Dec. 2014
regardless of change of search record. The prosomal width increased from 15-30
mm to 55-70 mm. As mentioned, the large juveniles might have reached a suitable
size for migrating from the nursery soft shore to subtidal habitat. From Mar.
to Sep. 2015, the size of major population decreased slightly to a prosomal
width 40-60 mm. At the same time, the number of individuals decreased
gradually. It further indicated some of large juveniles might have migrated to
sub-tidal habitat, leaving the smaller individuals on shore. There was an
overall growth trend. In Dec. 2015, two big individuals (prosomal width 89.27
mm and 98.89 mm) were recorded only while it could not represent the major
population. From Dec. 2015 to Mar. 2016, the number of individual was very few
in ST that no boxplot could be produced. In Jun. 2016, the prosomal width of
major population ranged 50-70 mm. But it dropped clearly to 30-40 mm in Sep.
2016 followed by an increase to 40-50 mm in Dec. 2016, 40-70 mm in Mar. 2017
and 50-60mm in Jun. 2017 (present survey). Based on overall higher number of
small individuals from Jun. 2016 to Jun. 2017, it indicated new round of
spawning. Throughout the monitoring period, the larger juveniles ranged 60-80
mm in prosomal width. Juveniles reaching this size would gradually migrate to
sub-tidal habitats.
3.6.37
As a
summary for horseshoe crab populations in TC3 and ST, there were spawning of Carcinoscorpius rotundicauda from 2014
to 2016 while the spawning time should be in spring. There were consistent,
increasing trends of population size in these two sampling zones. For Tachypleus tridentatus, small
individuals were rarely found in both zones from 2014 to 2015. It was believed
no occurrence of successful spawning. The existing individuals (that recorded
since 2012) grew to a mature size and migrated to sub-tidal habitat. Hence the
number of individuals decreased gradually. In 2016, new round of spawning was
recorded in ST while increasing number of individuals and body size was
noticed.
Impact of the HKLR project
3.6.38
It was the 19th survey of the EM&A
programme during the construction period. Based on the results, impact of the
HKLR project could not be detected on horseshoe crabs. The population change
was mainly determined by seasonal variation while new rounds of spawning were
observed for both species. In case, abnormal phenomenon (e.g. very few numbers
of horseshoe crab individuals in wet season, large number of dead individuals
on the shore) is found, it would be reported as soon as possible.
Seagrass
Beds
3.6.39
In the present survey, seagrass species Halophila
ovalis and Zostera japonica were recorded in TC3 and ST. Photo records were
shown in Figure 3.8 of Appendix N while the complete records of seagrass beds survey
were shown in Annex III of Appendix N.
3.6.40
Table 3.2 of
Appendix N summarizes the
results of seagrass beds survey. In TC3, two small patches of Halophila ovalis was found in soft mud
area at 0.5-1.0 m above C.D. while the total seagrass bed area and vegetation
coverage were about 140.4 m2 (average seagrass bed area 70.2 m2)
and 100% respectively.
3.6.41
In ST, two large patches of Halophila ovalis were found while the total seagrass bed area was
about 17046.5 m2. The largest patch was an extensive, horizontal
strand with area ~12334.4 m2 and vegetation coverage 80-100%,
located in the soft mud area at 0.5-2.0 m above C.D.. It had covered
significant portion of the mud flat area southward from TC3 boundary to ST
(i.e. western shore of Tung Chung Wan). At vicinity, there was another large
patch (4712.1 m2, coverage 80-100%), located in the sandy area at
1.0-2.0 m above C.D..
3.6.42
For Zostera
japonica, there was one, small horizontal strand in the sandy area nearby
the seaward mangrove. The seagrass bed area and vegetation coverage were 105.4
m2 and 100% respectively.
3.6.43 Since majority of seagrass bed was confined in ST,
the temporal change of both seagrass species was investigated in details.
Temporal variation
of seagrass beds
3.6.44
Figure 3.9 of Appendix N shows the
changes of estimated total area of seagrass beds in ST along the sampling
months. For Zostera japonica, it was not recorded in the 1st
and 2nd surveys of monitoring programme. Seasonal recruitment of
few, small patches (total seagrass area: 10 m2) was found in Mar.
2013 that grew within the large patch of seagrass Halophila ovalis. Then
the patch size increased and merged gradually with the warmer climate from Mar.
to Jun. 2013 (15 m2). However, the patch size decreased and remained
similar from Sep. 2013 (4 m2) to Mar. 2014 (3 m2). In
Jun. 2014, the patch size increased obviously again (41 m2) with
warmer climate followed by a decrease between Sep. 2014 (2 m2) and
Dec. 2014 (5 m2). From Mar. to Jun. 2015, the patch size increased
sharply again (90 m2). It might be due to the disappearance of the
originally dominant seagrass Halophila ovalis resulting in less
competition for substratum and nutrients. From Sep.2015 to Jun.2016, it was
found coexisting with seagrass Halophila ovalis with steady increasing
patch size (from 44 m2 to 115 m2) and variable coverage.
In Sep. 2016, the patch size decreased again to (38 m2) followed by
an increase to a horizontal strand (105.4 m2) in Jun. 2017 (present
survey). And it was no longer co-existing with Halophila ovalis. Between
Sep. 2014 and Jun. 2017, an increasing trend was noticed from Sep. to Jun. of
next year followed by a rapid decline in Sep. of next year. It was possibly the
causes of heat stress, typhoon and stronger grazing pressure during wet season.
3.6.45 For Halophila ovalis,
it was recorded as 3-4 medium to large patches (area 18.9-251.7 m2;
vegetation coverage 50-80%) beside the mangrove vegetation at tidal level 2 m
above C.D. in Sep. 2012 (first survey). The total seagrass bed area grew
steadily from 332.3 m2 in Sep. 2012 to 727.4 m2 in Dec.
2013. Flowers were observed in the largest patch during its flowering period.
In Mar. 2014, 31 small to medium patches were newly recorded (variable area
1-72 m2 per patch, vegetation coverage 40-80% per patch) in lower
tidal zone between 1.0 and 1.5 m above C.D. The total seagrass area increased
further to 1350 m2. In Jun. 2014, these small and medium patches
grew and extended to each other. These patches were no longer distinguishable
and were covering a significant mudflat area of ST. It was generally grouped
into 4 large patches (1116 ¡V 2443 m2) of seagrass beds characterized
of patchy distribution, variable vegetable coverage (40-80%) and smaller
leaves. The total seagrass bed area increased sharply to 7629 m2. In
Sep. 2014, the total seagrass area declined sharply to 1111 m2.
There were only 3-4 small to large patches (6-253 m2) at high tidal
level and 1 patch at low tidal level (786 m2). Typhoon or strong
water current was a possible cause (Fong, 1998). In Sep. 2014, there were two
tropical cyclone records in Hong Kong (7th-8th Sep.: no
cyclone name, maximum signal number 1; 14th-17th Sep.:
Kalmaegi, maximum signal number 8SE) before the seagrass survey dated 21st Sep.
2014. The strong water current caused by the cyclone, Kalmaegi especially,
might have given damage to the seagrass beds. In addition, natural heat stress
and grazing force were other possible causes reducing seagrass beds area.
Besides, very small patches of Halophila ovalis could be found in other
mud flat area in addition to the recorded patches. But it was hardly
distinguished due to very low coverage (10-20%) and small leaves.
3.6.46
In Dec. 2014, all the seagrass patches of Halophila ovalis disappeared in ST. Figure 3.10 of Appendix N shows the
difference of the original seagrass beds area nearby the mangrove vegetation at
high tidal level between Jun. 2014 and Dec. 2014. Such rapid loss would not be
seasonal phenomenon because the seagrass beds at higher tidal level (2.0 m
above C.D.) were present and normal in December 2012 and 2013. According to
Fong (1998), similar incident had occurred in ST in the past. The original
seagrass area had declined significantly during the commencement of the
construction and reclamation works for the international airport at Chek Lap
Kok in 1992. The seagrass almost disappeared in 1995 and recovered gradually
after the completion of reclamation works. Moreover, incident of rapid loss of
seagrass area was also recorded in another intertidal mudflat in Lai Chi Wo in
1998 with unknown reason. Hence Halophila ovalis was regarded as a
short-lived and r-strategy seagrass that could colonize areas in short period
but disappears quickly under unfavorable conditions (Fong, 1998).
Unfavourable
conditions to seagrass Halophila ovalis
3.6.47
Typhoon or strong
water current was suggested as one unfavourable condition to Halophila ovalis (Fong, 1998). As
mentioned above, there were two tropical cyclone records in Hong Kong in Sep.
2014. The strong water current caused by the cyclones might have given damage
to the seagrass beds.
3.6.48 Prolonged light deprivation due to turbid water
would be another unfavorable condition. Previous studies reported that Halophila
ovalis had little tolerance to light deprivation. During experimental
darkness, seagrass biomass declined rapidly after 3-6 days and seagrass died
completely after 30 days. The rapid death might be due to shortage of available
carbohydrate under limited photosynthesis or accumulation of phytotoxic end
products of anaerobic respiration (details see Longstaff et al., 1999).
Hence the seagrass bed of this species was susceptible to temporary light
deprivation events such as flooding river runoff (Longstaff and Dennison,
1999).
3.6.49 In order to
investigate any deterioration of water quality (e.g. more turbid) in ST, the
water quality measurement results at two closest monitoring stations SR3 and
IS5 of the EM&A programme were obtained from the water quality monitoring
team. Based on the results from June to December 2014, the overall water
quality was in normal fluctuation except there was one exceedance of suspended
solids (SS) at both stations in September. On 10th Sep., 2014, the
SS concentrations measured during mid-ebb tide at stations SR3 (27.5 mg/L) and
IS5 (34.5 mg/L) exceeded the Action Level (≤23.5 mg/L and 120% of upstream
control station¡¦s reading) and Limit Level (≤34.4 mg/L and 130% of upstream
control station¡¦s reading) respectively. The turbidity readings at SR3 and IS5
reached 24.8-25.3 NTU and 22.3-22.5 NTU respectively. The temporary turbid
water should not be caused by the runoff from upstream rivers. Because there
was no rain or slight rain from 1st to 10th Sep. 2014 (daily total rainfall at
the Hong Kong International Airport: 0-2.1 mm; extracted from the climatological
data of Hong Kong Observatory). The effect of upstream runoff on water quality
should be neglectable in that period. Moreover, the exceedance of water quality
was considered unlikely to be related to the contract works of HKLR according
to the ¡¥Notifications of Environmental Quality Limits Exceedances¡¦ provided by
the respective environmental team. The respective construction of seawall and
stone column works, which possibly caused turbid water, were carried out within
silt curtain as recommended in the EIA report. Moreover, there was no leakage
of turbid water, abnormity or malpractice recorded during water sampling. In
general, the exceedance of suspended solids concentration was considered to be
attributed to other external factors, rather than the contract works.
3.6.50 Based on the
weather condition and water quality results in ST, the co-occurrence of cyclone
hit and turbid waters in Sep. 2014 might have combined the adverse effects on Halophila ovalis that leaded to
disappearance of this short-lived and r-strategy seagrass species. Fortunately,
Halophila ovalis was a fast-growing
species (Vermaat et al., 1995).
Previous studies showed that the seagrass bed could be recovered to the
original sizes in 2 months through vegetative propagation after experimental
clearance (Supanwanid, 1996). Moreover, it was reported to recover rapidly in
less than 20 days after dugong herbivory (Nakaoka and Aioi, 1999). As
mentioned, the disappeared seagrass in ST in 1995 could recover gradually after
the completion of reclamation works for international airport (Fong, 1998). The
seagrass beds of Halophila ovalis
might recolonize the mudflat of ST through seed reproduction as long as there
was no unfavorable condition in the coming months.
Recolonization of
seagrass beds
3.6.51
Figure
3.10 of Appendix N shows the
recolonization of seagrass bed area in ST from Dec. 2014 to Jun. 2017. From
Mar. to Jun. 2015, 2-3 small patches of Halophila
ovalis were newly found coinhabiting with another seagrass species Zostera japonica. But its total patch
area was still very low relative to the previous records. The recolonization
rate was low while cold weather and insufficient sunlight were possible factors
between Dec. 2014 and Mar. 2015. Moreover, it would need to compete with
seagrass Zostera japonica for
substratum and nutrient. Since Zostera
japonica had extended and had covered the original seagrass bed of Halophila ovalis at certain degree. From
Jun. 2015 to Mar. 2016, the total seagrass area of Halophila ovalis had increased rapidly from 6.8 m2 to
230.63 m2. It had recolonized its original patch locations and
covered Zostera japonica. In Jun.
2016, the total seagrass area increased sharply to 4707.3 m2.
Similar to the previous records of Mar to Jun. 2014, the original patch area
increased further to a horizontally long strand. Another large seagrass beds
colonized the lower tidal zone (1.0-1.5 m above C.D.). In Sep. 2016, this patch
extended much and covered significant soft mud area of ST, resulting in sharp
increase of total area (24245 m2). It indicated the second extensive
colonization of this r-strategy
seagrass. In Dec. 2016, this extensive seagrass patch decreased in size and had
separated into few, undistinguishable patches. Moreover, the horizontal strand
nearby the mangrove vegetation decreased in size (Figure 3.10 of Appendix N). The total seagrass bed decreased to
12550 m2. In Mar. 2017, the seagrass bed area remained stable (12438
m2) while the vegetation coverage decreased clearly (20-50%). It was
once predicted that the seagrass bed area would continue to decrease, similar
to the record in Sep-Dec. 2014. However, it increased in both area (17046.5 m2)
and vegetation coverage (80-100%) in Jun. 2017 (present survey).
Impact of the HKLR project
3.6.52 It was the 19th
survey of the EM&A programme during the construction period. According to
the results of present survey, there was clear recolonization of both seagrass
species Halophila ovalis and Zostera japonica in ST. Hence the
negative impact of HKLR project on the seagrass was not significant. In case
unfavorable phenomenon (e.g. reduction of seagrass patch size, abnormal change
of leave color) is found persistent, it would be reported as soon as possible.
Intertidal Soft Shore Communities
3.6.53
Table 3.3 and Figure 3.11 of Appendix N show the types of substratum along the
horizontal transect at every tidal level in all sampling zones. The relative
distribution of different substrata was estimated by categorizing the
substratum types (Gravels & Boulders / Sands / Soft mud) of the ten random
quadrats along the horizontal transect. The distribution of substratum types
varied among tidal levels and sampling zones:
¡P
In TC1, high percentages of ¡¥Gravels and Boulders¡¦
(70-80%) were recorded at all tidal levels. The minor substratum types were
'Sands' (20% at high and low tidal levels) and 'Soft mud' (10-20% at low and
mid tidal levels).
¡P
In TC2, the major substratum type was ¡¥Sands¡¦ (60%)
at high tidal level followed by 'Gravels and Boulders' (30%). The substratum
types were recorded evenly at mid tidal level ('Soft mud' 40%, 'Sands' 30%,
'Gravels and Boulders' 30%). At low tidal level, the major substratum type was
'Soft mud' (70%) followed by 'Gravels and Boulders' (20%)
¡P
In TC3, high percentages of ¡¥Sands¡¦ (90-100%) were
recorded at high and mid tidal levels. At low tidal level, the major substratum
type was ¡¥Gravels and Boulders¡¦ (90%).
¡P
In ST, high percentages of ¡¥Gravels and Boulders¡¦
(80-100%) were recorded at high and mid tidal levels. At low tidal level, the
substratum types were recorded evenly ('Sands' 40%, 'Soft mud' 30%, 'Gravels
and Boulders' 30%).
3.6.54
There
was neither consistent vertical nor horizontal zonation pattern of substratum
type in all sampling zones. Such heterogeneous variation should be caused by
different hydrology (e.g. wave in different direction and intensity) received
by the four sampling zones.
3.6.55
Table 3.4 of Appendix N lists the total abundance, density and
number of taxon of every phylum in this survey. A total of 16420 individuals
were recorded. Mollusca was clearly the most abundant phylum (total abundance
15648 ind., density 522 ind. m-2, relative abundance 95.3%). The
second and third abundant phyla were Arthropoda (578 ind., 19 ind. m-2,
3.5%) and Annelida (91 ind., 3 ind. m-2, 0.6%) respectively.
Relatively other phyla were very low in abundances (density ≤1 ind. m-2,
relative abundance ≤0.2%). Moreover, the most diverse phylum was Mollusca (40
taxa) followed by Arthropoda (14 taxa) and Annelida (11 taxa). There were 1-3
taxa recorded only for other phyla. The taxonomic resolution and complete list
of collected specimens are shown in Appendix IV and V respectively.
3.6.56
Table 3.5 of Appendix N
shows the number of individual, relative abundance and density of each phylum
in every sampling zone. The total abundance (2830-5517 ind.) varied among the
four sampling zones while the phyla distributions were similar. In general,
Mollusca was the most dominant phylum (no. of individuals: 2589-5336 ind.;
relative abundance 91.5-97.0%; density 345-711 ind. m-2). Other
phyla were much lower in number of individuals. Arthropoda was the second
abundant phylum (119-172 ind.; 2.2-5.8%; 16-23 ind. m-2). Annelida
was the third abundant phylum in TC2 and TC3 (33-40 ind.; 0.6-1.4%; 4-5 ind. m-2).
Nemertea was relatively common in TC2 (17 ind.; 0.6%; 2 ind. m-2).
Relatively other phyla were low in abundance in all sampling zones (≤ 0.5%).
Dominant
species in every sampling zone
3.6.57
Table 3.6
of Appendix N lists the abundant
species (relative abundance >10%) in every sampling zone. In the present
survey, most of the listed abundant species were of low to moderate densities
(50-250 ind. m-2). Few listed species of high or very high density
(> 250 ind. m-2) were regarded as dominant species. Other listed species of
lower density (< 50 ind. m-2) were regarded as common species.
3.6.58
In TC1,
the major substratum was ¡¥Gravels and Boulders¡¦ at all tidal levels. The most
abundant gastropod was Batillaria
multiformis at moderate-high densities (248-291 ind. m-2,
relative abundance 35-50%) at high and mid tidal levels. Another abundant
gastropod Cerithidea djadjariensis
was at moderate densities (84-155 ind. m-2, 12-26%) at all tidal
levels. Gastropod Monodonta labio
(138-209 ind. m-2, 24-29%) and rock oyster Saccostrea cucullata (78-104 ind. m-2, 11-18%, attached
on boulders) were at moderate densities at mid and low tidal levels.
3.6.59
In TC2,
gastropod Cerithidea djadjariensis
(297 ind. m-2, 60 %) was abundant at moderate-high density at high
tidal level (major substratum: 'Sands') followed by common gastropod Batillaria multiformis (50 ind. m-2,
10 %). Moreover, gastropod Cerithidea
djadjariensis was also abundant at moderate density (164 ind. m-2,
42 %) at mid tidal level (major substrata: 'Sands' and 'Soft mud') with common
gastropod Batillaria zonalis (64 ind.
m-2, 16 %) and rock oyster Saccostrea
cucullata (44 ind. m-2, 11 %). There was no clearly abundant species at low
tidal level (major substratum: 'Soft mud'). There were few common taxa at
low-moderate densities such as gastropods Cerithidea
djadjariensis (62 ind. m-2, 25 %), Batillaria zonalis (39 ind. m-2, 16 %), rock oyster Saccostrea cucullata (49 ind. m-2,
20 %) and barnacle Balanus amphitrite
(38 ind. m-2, 15 %, attached on boulders).
3.6.60 In TC3, the major substratum was ¡¥Sands¡¦ at both high and mid tidal
levels. Gastropod Cerithidea djadjariensis was dominant species of high
densities (412-444 ind. m-2, 53-57 %) followed by two abundant
gastropods Batillaria multiformis (142-185 ind. m-2, 18-24 %)
and Cerithidea cingulata (98-130 ind. m-2, 13-17 %). At low
tidal level (major substratum: ¡¥Gravels and Boulders¡¦), rock oyster Saccostrea
cucullata (265 ind. m-2, 40%) and gastropod Monodonta labio
(194 ind. m-2, 30%) were abundant at moderate densities.
3.6.61
In ST,
gastropod Batillaria multiformis was
abundant at moderate density (207 ind. m-2, 35 %) followed by Monodonta labio (143 ind. m-2,
24 %) and limpet Cellana toreuma (97
ind. m-2, 16 %) at high tidal level (major substratum: ¡¥Gravels and
Boulders¡¦). At mid tidal level (major substratum: ¡¥Gravels and Boulders¡¦),
there were gastropods Monodonta labio
(90 ind. m-2, 18 %), Cerithidea
djadjariensis (82 ind. m-2, 16 %) and rock oyster Saccostrea cucullata (88 ind. m-2,
18%) at low-moderate densities. No single species was clearly abundant at low
tidal level (major substrata: ¡¥Sands¡¦ and ¡¥Soft mud¡¦). The gastropod Cerithidea djadjariensis was at
low-moderate density (75 ind. m-2, 28 %) followed by common
gastropod Lunella coronata (42 ind. m-2,
16%) and rock oyster Saccostrea cucullata
(37 ind. m-2, 14%).
3.6.62
In
general, there was no consistent zonation pattern of species distribution
across all sampling zones and tidal levels. The species distribution should be
determined by the type of substratum primarily. In general, gastropods Cerithidea djadjariensis (total number
of individuals: 4746 ind., relative abundance 28.9%), Batillaria multiformis (3076 ind., 18.7%), Cerithidea cingulata (1015 ind., 6.2%) and Batillaria zonalis (519 ind., 3.2%) were the most commonly
occurring species on sandy and soft mud substrata. Rock oyster Saccostrea cucullata (1887 ind., 11.5%),
gastropods Monodonta labio (2181
ind., 13.3%) and Lunella coronata
(473 ind., 2.9%) were commonly occurring species inhabiting gravel and boulders
substratum.
Biodiversity and abundance of soft shore
communities
3.6.63
Table 3.7 of Appendix N shows the mean values of species number, density,
biodiversity index H¡¦ and species
evenness J of soft shore communities
at every tidal level and in every sampling zone. As mentioned above, the
differences among sampling zones and tidal levels were determined by the major
type of substratum primarily.
3.6.64
Among the sampling
zones, the mean species numbers (10-12 spp. 0.25 m-2) and J (0.6-0.7) were similar. The mean
densities of TC1 and TC3 (625-736 ind. m-2) were higher than TC2 and
ST (377-451 ind. m-2). Due to different density, the mean H¡¦ of ST (1.7) was higher than that of TC1,
TC2 (1.5) and TC3 (1.2).
3.6.65
Across the tidal
levels, there was no consistent difference of the mean species number and H' in all sampling zones. For the mean
density, there were generally decreasing trends in TC2, TC3 and ST from high to
low tidal level. For the mean J,
there was a slightly increasing trend from high to low tidal level in all
sampling zones.
3.6.66
Figures 3.12-3.15 of Appendix N show the temporal changes of mean species number,
mean density, H¡¦ and J at every tidal level and in every
sampling zone along the sampling months. In general, all the biological
parameters fluctuated seasonally throughout the monitoring period. Lower mean
species number and density were recorded in dry season (Dec.) but the mean H' and J fluctuated within a stable range.
3.6.67
Focusing on the
changes of mean density in ST, there were steady decreasing trends regardless
of tidal levels since the beginning of monitoring period. It might be an
unfavourable change that reflected environmental stresses. However, the mean
densities increased again from Dec. 2016 to Jun. 2017 (present survey). The
faunal populations were believed in recovery.
Impact of the HKLR project
3.6.68
It was the 19th survey of the EM&A
programme during the construction period. Based on the results, impacts of the
HKLR project were not detected on intertidal soft shore community. In case of
other abnormal phenomena (e.g. rapid or consistent decline of fauna densities
and species number) are observed, it would be reported as soon as possible.