6.                  Marine ecology

 

6.1              Introduction

 

6.1.1          The marine ecological impact assessment conducted for this Study concluded that impacts from the proposed development were mainly associated with the direct loss of marine habitats due to reclamation and CBL construction. In terms of ecological importance, ecological assessment indicated that the affected habitats were generally of low ecological value.  Indirect marine ecological impacts were assessed with reference to worst-case scenario water quality modelling predictions for relatively small scale and short duration dredging works only required during Phase I of the reclamation. With implementation of constraints and mitigation measures for dredging, it was concluded that adverse indirect marine ecological impacts on marine ecological sensitive receivers were not expected.

6.1.2          Measures to minimise and compensate identified marine ecological impacts have been recommended. Details on the marine ecological mitigation measures and monitoring requirements that must be followed are set out below. The implementation schedule for the mitigation measures is presented in Appendix C

 

6.2              Marine Ecological Mitigation Measures and Monitoring

 

Construction phase direct coral impacts

 

6.2.1          Recent surveys of hard substrata subtidal habitats directly affected by WCR reclamation reveal very low coverage by corals (typically, hard coral coverage was less than 1%, and octo-coral from 0 – 15%), with only common species recorded, and these habitats were considered of low ecological value. It is recommended however that the feasibility of transplanting potentially impacted hard corals from the reclamation area to suitable nearby habitats is investigated during the detailed design stage of the Project. To achieve this aim, surveys of the proposed reclamation area should be conducted during the detailed design stage, at least 8 months prior to the start of the construction phase. These surveys should focus on identifying and mapping hard corals that would be suitable for transplantation (i.e., corals encrusting small boulders of a manageable size that can be moved by divers with lifting aids). If corals suitable for transplantation are identified during these surveys, a detailed transplantation methodology (including monitoring of transplanted corals) should be drafted during the detailed design stage of the Project. Coral identification and mapping work should be conducted by a qualified marine biologist with specialist knowledge of corals and sound experience at identifying sessile benthic taxa in the field whilst using self-contained underwater breathing apparatus. Preferably, the specialist should hold a post-graduate degree in marine biology. The marine specialist, dive survey and coral translocation methods should be proposed by the ET in agreement with the IEC and should be approved by AFCD prior to the commencement of monitoring programme.

Construction phase indirect coral impacts

 

6.2.2          The proposed WCR reclamation would be constructed in 3 phases and would involve a construction sequence and methods that are designed to lessen resulting water quality impacts due to dispersion of suspended sediments. The major source of water quality impact arising from the Project, which may impact coral sites in Junk Bay, would be associated with Phase I of WCR reclamation works owing to the need to dredge the seabed. In contrast, no dredging would be required for Phase II and Phase III of the WCR reclamation and water quality impact that would be associated with other construction activities such as filling and bored piling was considered to be negligible. During the construction phase, mitigation measures used to control water quality would serve to protect marine habitats in proximity to the reclamation to acceptable levels. 

6.2.3          Mitigation measures and constraints to control water quality are set out in Section 4 of this EM&A Manual, which includes deployment of a silt curtain and controls on dredging rate to minimise impacts from dredging activity during Phase I of the WCR reclamation.

Construction Phase Coral Monitoring

 

Objectives

 

6.2.4          Although adverse impacts to coral sites due to the Project works were not predicted to occur, nevertheless it was recommended that monitoring should be implemented during dredging works for Phase I of the WCR reclamation and this should be focused on the coral sites in Junk Bay.  The main objective of this monitoring would be to verify the EIA predictions that no adverse impacts have occurred. In the event that adverse impacts were identified and were a consequence of the works, monitoring would also allow for implementation of appropriate actions to reduce such impacts. 

Monitoring Locations

 

6.2.5          In the vicinity of the construction works, the closest coral sites were located at the Southwest Junk Bay and at Junk Island.  These corals sites will constitute the impact monitoring stations for this construction phase coral monitoring programme.  As described in the EIA Report, surveys conducted in 1999 and 2003 indicated these sites were dominated by soft and gorgonian corals with low cover of hard corals.

6.2.6          In order to identify background environmental perturbations during the monitoring that are not associated with the Project, coral monitoring should also be conducted at a control site. The coral site at East Joss House Bay was considered to be suitable coral monitoring control station.  It was considered that this site is located at a sufficient distance from the marine works where no water quality impact associated with Project would be possible. As described in the EIA Report, according to surveys conducted in 1999 and 2003, the East Joss House Bay coral site comprised a moderate cover of hard corals and some soft /gorgonian corals. Comparison of monitoring data from impact and control stations can be used to determine the source of impacts in addition to examination of water quality monitoring results.

6.2.7          The general location for coral monitoring at the 3 monitoring sites is provided in Figure 6.1. 

General Requirements

 

6.2.8          The construction phase coral monitoring programme should comprise:

·        Baseline Survey / Coral Tagging Exercise

·        Impact Monitoring Surveys

 

6.2.9          Impact monitoring surveys will be conducted once per week at each coral monitoring site for the duration of dredging activities for Phase I of the WCR reclamation. The tentative construction programme indicates dredging activities would occur for approximately 1 month.

6.2.10      Coral monitoring work should be conducted by a qualified marine biologist with specialist knowledge of corals and sound experience at identifying sessile benthic taxa in the field whilst using self-contained underwater breathing apparatus. To ensure consistency, it is recommended that the same coral specialist should be used on each dive survey. Preferably, the specialist should hold a post-graduate degree in marine biology. The coral specialist should be hired by the ET in agreement with IEC and should be approved by AFCD prior to the commencement of the monitoring programme.

Baseline Survey / Coral Tagging Exercise Methodology

 

6.2.11      A baseline survey and coral tagging exercise should be conducted preferably no more than one month before commencement of dredging at Phase I of the WCR Reclamation. At each coral monitoring station, a reconnaissance survey should be conducted to collect information on the abundance, diversity and health status (bleaching, partial mortality and silt cover etc.).  The information gained in the reconnaissance survey should be used to identify the number and coral colonies suitable for tagging.  The ET should discuss and agree the basis of appropriate selection of corals for tagging with the IEC and should be approved by AFCD prior to the commencement of fieldwork for the coral monitoring programme.

6.2.12      In general, tagging of a minimum of 20 hard coral colonies and 20 soft/gorgonian coral colonies at each coral monitoring station is considered appropriate.  Corals should be tagged giving priority to the largest, undamaged colonies since damage to these colonies would be more evident compared to corals with existing damage. Corals should also be selected for tagging based on the most suitable coral species and growth forms. As far as possible, tagging of hard coral species with tall polyps should be avoided due to their higher tolerance of sedimentation.

6.2.13      Coral colonies should be tagged using small brightly coloured (e.g. orange or green) stones marked with labelled mahjong tags. Furthermore, a matching numbered tag should be nailed into hard substrata (boulder or bedrock) close to each tagged coral.   A fine rope trial should be laid down linking all tagged colonies or bearings and distance between colonies should be taken to aid re-location at each monitoring station.

6.2.14      For each tagged coral, specific detailed information should be collected including location, size, depth and general condition of their immediate surroundings.  For soft/gorgonian corals, information collected should include height and number of branches. Tagged coral colonies should also be identified to the highest taxonomic resolution practicable. The condition of each tagged coral colony should also be recorded by taking a photograph from an angle that best represents the entire colony.

6.2.15      For each tagged hard coral colony, sediment cover should be recorded including percentage cover, colouration, texture and approximate thickness of sediment on the colony itself and on adjacent hard substrate.  Any contiguous patches of sediment cover >10% should be counted. To aid percentage cover estimates, a 50 cm x 50 cm quadrat equipped with 10cm spaced string grid should be used.

6.2.16      The health status of each tagged coral colony should be carefully recorded.  For hard corals, this should include information on existing surface area with partial mortality and bleached area. For soft/gorgonian corals the percentage of branches affected by partial mortality should be recorded.

6.2.17      Coral tissue death (recorded as total or partial mortality) may occur due to sediment deposition, bleaching or predation, bacterial infection, etc. The skeletal areas where tissue mortality had occurred may be rapidly overgrown by algae or colonised by ‘fouling’ organisms.  Dead skeletal areas on hard corals would appear white if recently dead but will taken a duller colouration within a few days as sediment and algae settle/grow on the dead area. On gorgonian coral, exposed coral skeleton is black.

6.2.18      For hard corals, two categories of bleached area should be recorded:

·        Blanched (i.e. paled)

·        Bleached (i.e. bleached white)

 

6.2.19      Blanched coral tissue on tagged hard corals should also be recorded. Blanched coral tissue would appear pale due a loss of zooxanthallae or photosynthetic pigments.  In contrast, bleached areas would appear white due to the white colouration of the skeleton visible through the transparent coral tissue. This bleaching would occur due to total loss of zooxanthellae. The coral tissue would still be present. It is possible that the lower portions of the coral tissue remain unbleached and would therefore help in differentiating bleached areas as opposed to partial mortality areas where the coral tissue would be absent.

6.2.20      In addition, physical damage, tissue distension, mucus production, and other parameters considered pertinent (e.g. presence of coralivorous gastrapods such as parasitic ovulids or Drupella sp. on damaged tissue areas) should also be recorded during surveys.

Impact Monitoring Survey Methodology

 

6.2.21      Impact monitoring is required to determine whether impacts are occurring on tagged corals during the period of marine works in particular due to sedimentation.  

6.2.22      Dive surveys for impact monitoring should collect the same information for tagged corals as the baseline survey.  Information gathered during each impact monitoring survey should include observations on the health status of corals and percentage cover and thickness of sediment.  It should also include condition of the tagged corals surroundings as well as weather, sea and tidal conditions.  Each tagged coral should be photographed as far as possible maintaining the same aspect and orientation as photographs taken for the baseline survey. Monitoring parameters should be recorded on a pre-printed sheet of underwater paper during the survey.  The position and extent of measurable parameters should be sketched on laminated photographs of the tagged coral colony.  These sketches should be compared to photographs to verify the field observations when compiling the data.

6.2.23      The results of the impact monitoring surveys should be reviewed with reference to findings of the water quality monitoring.

6.2.24      All tags at the impact and control stations should be removed/retrieved after the monitoring is completed.

Compliance / Action Event Action Plan

 

6.2.25      Coral monitoring results should be evaluated against Action and Limit Levels.  Evaluation should be based on recorded changes in

·         Percentage of partial mortality (hard corals and soft/gorgonian corals separately)

·         Percentage of sediment cover (hard corals only)

·         Percentage of bleaching (bleached white) (hard corals only)

 

6.2.26      Action and Limit Levels are defined in Table 6.1. These Levels are based on previously used protocols for EM&A programmes[1] in Hong Kong which have been demonstrated effective at guarding corals from unacceptable impacts from marine dredging or jetting works.

Table 6.1         Action and Limit Level for Coral Monitoring

 

Action Level Definition
  • If during Impact Monitoring a 15% increase in the percentage of sediment cover on hard corals occurs at more than 20% of the tagged hard coral colonies at either of the Impact Monitoring Stations that is not recorded at the Control Monitoring Station, then the Action Level is exceeded.
  • If during Impact Monitoring a 15% increase in the percentage of bleaching on hard corals occurs at more than 20% of the tagged coral colonies at either of the Impact Monitoring Stations that is not recorded at the Control Monitoring Station, then the Action Level is exceeded.
  • If during Impact Monitoring a 15% increase in the percentage of partial mortality on hard corals occurs at more than 20% of the tagged hard coral colonies at either of the Impact Monitoring Stations that is not recorded at the Control Monitoring Station, then the Action Level is exceeded.
  • If during Impact Monitoring a 15% increase in the percentage of partial mortality on soft/gorgonian corals occurs at more than 20% of the tagged soft/gorgonian coral colonies at either of the Impact Monitoring Stations that is not recorded at the Control Monitoring Station, then the Action Level is exceeded.

 

Limit Level Definition
  • If during the Impact Monitoring a 25% increase in the percentage of sediment cover at more than 20% of the tagged hard coral colonies occurs that is not recorded at the Control Monitoring Station, then the Limit Level is exceeded.
  • If during the Impact Monitoring a 25% increase in the percentage of bleaching (bleached white) at more than 20% of the tagged hard coral colonies occurs that is not recorded at the Control Monitoring Station, then the Limit Level is exceeded.
  • If during the Impact Monitoring a 25% increase in the percentage of partial mortality at more than 20% of the tagged hard coral colonies occurs that is not recorded at the Control Monitoring Station, then the Limit Level is exceeded.
  • If during the Impact Monitoring a 25% increase in the percentage of partial mortality at more than 20% of the tagged soft/gorgonan coral colonies occurs that is not recorded at the Control Monitoring Station, then the Limit Level is exceeded.

 

6.2.27      If the defined Action Level or Limit Levels for coral monitoring are exceeded, the stepwise procedures set out in Table 6.2 should be implemented.

Reporting

6.2.28      A baseline survey report should be compiled and certified by IEC and submitted to AFCD prior to the commencement of marine works.

6.2.29      Coral monitoring findings and results should be reported in the appropriate month’s EM&A report to be certified by IEC and submitted to AFCD for consideration.  Interpretation of coral monitoring results should make reference to water quality monitoring results.

Table 6.2         Action and Limit Level Exceedance  Procedures for Construction Phase Coral Monitoring

Event

ET Leader

IC(E)

ER

Contractor

Action Level Exceedance

Step 1 - Compare  results with water quality monitoring results and repeat coral survey event within 2 days. If Action Level is still exceeded notify AFCD.

Step 2 - Inform the IC(E), ER and Contractor and discuss the most appropriate method of reducing suspended solids during marine works (e.g. reduction of dredging rate, increase effectiveness of silt curtain)

Step 3 - Ensure mitigation measures are implemented and repeat survey after mitigation measure enacted for confirmation of compliance.

Step 4 - If non-compliance continues, increase mitigation measures (Step 2) and repeat monitoring survey measurements (Step 3).  If non-compliance occurs a third time suspend marine works.

 

Discuss with ET and Contractor on the mitigation measures;

Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly;

Assess the effectiveness of the implemented mitigation measures.

Discuss with IC(E) on the proposed mitigation measures;

Make agreement on the mitigation measures to be implemented;

Assess the effectiveness of the implemented mitigation measures.

Inform the Engineer and confirm notification of the non-compliance in writing;

Rectify unacceptable practice;

Check all plant and equipment; Consider changes of working methods;

Discuss with ET and IC(E) and propose mitigation measures to IC(E) and ER within three working days;

Implement the agreed mitigation measures.

Limit Level Exceedance

Undertake Steps 1-3 immediately. If further non-compliance continues at Limit Level, suspend marine works until an effective solution is identified

Discuss with ET and Contractor on the mitigation measures;

Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly;

Assess the effectiveness of the implemented mitigation measures.

Discuss with IC(E) on the proposed mitigation measures;

Make agreement on the mitigation measures to be implemented;

Assess the effectiveness of the implemented mitigation measures.

Inform the Engineer and confirm notification of the non-compliance in writing;

Rectify unacceptable practice;

Check all plant and equipment; Consider changes of working methods;

Discuss with ET and IC(E) and propose mitigation measures to IC(E) and ER within three working days;

Implement the agreed mitigation measures.

Grassy Puffers

 

6.2.30      The Grassy Puffer (Takifugu niphobles) is an IUCN listed species that normally live in open water but may deliberately strand in a high shore intertidal rock pool at spring tide located on the Chui Keng Wan rocky shore in order to spawn, where they may remain until the next spring tide.   Mitigation to prevent potentially lethal direct impact of construction activities on individual Grassy Puffers, if found stranded in rock pools is required. 

6.2.31      It is recommended that the rock pool is visited after each spring tide (i.e. about every 2 weeks) during the construction phase of the WCR reclamation until the shore is no longer available due to filling associated with the Project. Any puffers present in the pool should be captured and transferred to a temporary holding tank. Captured fish should be returned to the sea outside the project works boundary. Owing to their defence mechanism of self-inflating, particular care should be employed when capturing and releasing the puffer fish (i.e. keeping the fish submerged in water at all times to prevent gulping of air, which could be lethal).   Details of mitigation plans to rescue stranded puffers should be drafted at the detailed design stage. A specialist with marine ecology background is necessary for carrying out the recommended monitoring. The specialist and mitigation plan should be submitted to AFCD for consideration and approval.

 

Hard substrata subtidal habitat compensation

 

6.2.32      Direct loss of marine habitats due to the Project, has been minimised to the largest possible extent within the constraints of engineering feasible design considerations.  Moreover, the proposed project which limits reclamation to the northwest coast of the remaining sea area of Junk Bay is itself mitigation to avoid higher ecological impacts on significant coral areas located at the southwest coast of Junk Bay of the previously investigated coastal road alignment.

6.2.33      To provide suitable substrata for recolonisation by marine organisms, the seawall of the proposed WCR reclamation was recommended to be of a rubble mound design. Elsewhere in Hong Kong seawall habitat have been found to be suitable to support marine organisms including coral growth. The rubble mound seawall consisting of haphazardly arranged boulders is expected to provide a large amount of hard substrata and increased surface area suitable for settlement and recruitment of coral assemblages similar to those previously recorded from this coast.

 

Rubble-Mound Seawall Recolonisation Monitoring

 

Objectives

 

6.2.34      In order to mitigate for the direct loss of existing hard substrata subtidal habitat that was found to support a low cover of mainly octo- and soft corals, the seawall was recommended to be of rubble-mound design. This seawall design was considered to provide suitable substrata for coral colonisation.

6.2.35      Monitoring was recommended with the objective of assessing the effectiveness of this mitigation measure and providing information on the rate of coral colonisation. The monitoring will study recolonisation on the shallow and deep areas on the rubble-mound seawall.

Monitoring Locations

                                 

6.2.36      Coral recolonisation monitoring should be conducted on the rubble-mound seawall constructed for the WCR reclamation on the northwest coast of Junk Bay. Monitoring will be conducted along six permanently marked 100m long by 1m wide belt transects (i.e. ~0.5m either side of the transect line). The ends of each transect should be marked by securely inserting/fixing steel stakes on the seawall. The start and end positions of the transects should be recorded using a portable Global Positioning System (GPS) unit.

6.2.37      The precise location of the transects should be determined by the ET following reconnaissance dives to identify suitable and representative areas on the seawall. Nevertheless, transect deployment on the seawall should be subdivided as follows:

·         3 x 100m transects to be laid parallel to the shoreline at shallow depths of (–2 to –5mPD)

·         3 x 100m transects to be laid parallel to the shoreline at deep depths (–7 to –10mPD)

General Requirements

 

6.2.38      Installation of the permanent transects and monitoring at the seawall should commence 3 months after completion of the marine construction works of the Project.  Following this, monitoring surveys should be conducted at 6-monthly intervals for the duration of a further 2.5 years (i.e. 6 monitoring surveys in total).

6.2.39      The coral recolonisation monitoring work should be conducted by a qualified marine biologist with specialist knowledge of corals and sound experience at identifying sessile benthic taxa in the field whilst using self-contained underwater breathing apparatus. To ensure consistency, it is recommended that the same coral specialist should be used on each dive survey. Preferably, the specialist should hold a post-graduate degree in marine biology. The coral specialist will be hired by the ET in agreement with the IEC and should be approved by AFCD prior to the commencement of the monitoring programme

Coral Recolonisation Monitoring Methodology

 

6.2.40      Dive surveys to monitor coral recolonisation will employ both semi-quantitative and quantitative methodologies. Each transect should be surveyed using Rapid Ecological Assessment techniques (see [2]DeVantier et al. 1998), which in addition will include enumeration of coral colonies.

6.2.41      Along each transect, an assessment of the benthic cover (Tier I) and taxon abundance (Tier II) should be conducted:

·         Tier I will assess the relative cover of major benthic groups and substrata

·         Tier II will provide an inventory of sedentary/ sessile benthic taxa, which are also ranked in terms of their abundance in the community inside the belt transect.

 

6.2.42      Under Tier I, the relative cover of major benthic groups and substrata should be assessed using the ecological and substrata attribute categories and ranks presented in Table 6.3a and 6.3b respectively.

Table 6.3a Tier 1 benthic attribute categories

Ecological Attributes

Substratum Attributes

 

Hard Coral

 

Bedrock

 

Dead Standing Corals

 

Boulders

 

Octocorals (soft corals and gorgonians)

 

Cobbles

 

 

Anemone Beds

 

Rubble (Shell/dead coral fragments)

 

Other Benthos (sponges, zoanthids,

Ascidians, bryozoans etc.)

 

Mud/silt

 

Macro-algae

 

Sand

 

Table 6.3b. Tier I ordinal ranks of percentage cover of benthic attributes

Rank

Percentage Cover

0

None recorded

0.5

1-5%

1

6-10%

2

11-30%

3

31-50%

4

51-75%

5

76-100%

 

 

6.2.43      Under Tier II, an inventory of benthic taxa should be compiled during the survey of each transect. Identification of taxa should be conducted in situ at least to the taxonomic resolution presented in Table 6.4. Representative photographs of corals and other representative benthic taxa should also be taken. 

Table 6.4. Taxonomic resolution of inventory

Type of Benthos

Taxonomic level of identification

Scleractinian corals

Species level, wherever possible

Octocorals, anemones, conspicious macro-algae

Genus level

Others (such as sponges, zoanthids, ascidians etc.)

Genus level or phylum level with description on the growth form and other characteristics

 

6.2.44      For each transect, each taxon in the inventory should be ranked in terms of abundance in the community. The taxon categories will be ranked in terms of relative abundance of individuals, rather than the contribution to benthic cover along each transect.  The ranks are visual assessments of abundance, rather than quantitative counts of each taxon. The ranks to be assigned each identified taxon in the inventory list are presented in Table 6.5.

Table 6.5 Ordinal ranks of taxon abundance

Taxon Abundance Rank

Abundance

0

Absent

1

Rare

2

Uncommon

3

Common

4

Abundant

5

Dominant

 

 

6.2.45      During the REA surveys, in addition to assessing the percentage cover and relative abundance of corals, the numerical abundance of colonies of each coral taxon along each transect should also be recorded. Other pertinent information such as size and tissue damage/mortality should also be noted.

6.2.46      In order to provide a permanent record of the condition of the rubble-mound seawall and to confirm the composition of benthic taxa present, video footage of each transect should be taken. The video camera should be held above the transect at a height of approximately 50cm and at an 45° angle to provide a landscape view of the survey area as observed by the divers. Video footage along the transect should be taken at a roughly constant rate of a distance no more than 10m per minute.

Reporting

 

6.2.47      A report detailing the survey findings should be submitted to AFCD following each survey. As appropriate, discussion should include comparison of conditions with the previous monitoring surveys to document the rate of recolonisation and effectiveness of rubble mound seawall as a mitigation measure.


[1] EM&A progammes involving coral monitoring during dredging or cable laying activities include:

Civil Engineering Department (2001) Focused cumulative water quality impact assessment of sand dredging at the West Po Toi Marine Borrow Area

CLP Power (2002) Environmental consultancy services for the proposed 132 kV cable circuits from A Kung Wan to Sai Kung Pier

Hong Kong and China Gas Company (2003) The Proposed Submarine Gas Pipelines from Cheng Tou Jiao Liquefied Natural Gas Receiving Terminal, Shenzhen to Tai Po Gas Production Plant, Hong Kong

[2] DeVantier, L.M., G. De’ath, T.J. Done and Turak, E. (1998).  Ecological Assessment of a Complex Natural System: A Case Study from the Great Barrier Reef.  Ecological Applications 8:480-496.