7                          MARINE ECOLOGY IMpact

7.1                    Introduction

7.1.1               The marine ecological impact assessment conducted for this Project concluded that impacts from the proposed marine works were mainly associated with the direct loss of marine habitats and associated marine life due to dredging activities at the Kowloon Bay. To avoid direct loss or damage of any species of conservation interest, translocation of the existing coral colonies within the proposed dredging areas that would be directly affected by proposed dredging works was recommended in the assessment. In terms of ecological importance, the assessment indicated that the affected habitats were considered as generally very low in ecological values and direct impact on some isolated coral colonies would be mitigated by coral translocation, no adverse direct impact on marine ecological resources is expected to occur.

7.1.2               Other indirect impacts on marine ecology arising from this Project are considered temporary and minor in nature. With the implementation of appropriate mitigation measures (e.g. water quality and noise control measures, coral translocation and re-construction of new artificial seawalls), it was concluded that ecological impact on marine life and species of conservation interest such as corals would be minor and acceptable under this Project.

 

7.2                    Mitigation measures for corals

 

Measure for direct coral impacts

 

7.2.1               Recent dive surveys included spot-check reconnaissance dives and Rapid Ecological Assessment (REA) were carried out in April 2007. Spot-check reconnaissance dives were first conducted to identify the extent of hard substrate with an emphasis on gaining an overview of coral occurrence within and adjacent to the proposed dredging area.  Areas with signs of coral colonies identified in spot-check dives were then further surveyed using REA technique along 100 m transect. 

7.2.2               Twenty transects in and within the vicinity of the proposed dredging area were surveyed during the spot-check surveys and information on GPS location, transect distance, visibility, substrate type, presence of coral colony and other invertebrates, and estimated size, percent cover and condition of coral were recorded. Transects with signs of coral colonies observed in the spot-check dives were further surveyed by REA.  A 100 m horizontal transect was laid follow the contour of seabed at each eight selected transects and benthic cover, taxon abundance, and ecological attributes within a swathe of 2 m wide, with 1 m of either side of the transects, were recorded following the REA technique as described in DeVantier et al. (1998). Photographs of seabed condition and representative coral colonies in the each surveyed sites were taken using an underwater digital camera. Information concerning the physical nature of the surveyed sites such as the degree of wave exposure of the sites, the nature of the substrate type and the topographic profile of the sites was recorded during the REA survey.

7.2.3               Recent surveys revealed that coral colonies that would be directly affected by the proposed dredging works was low in species diversity (only one species) and coverage (1 – 5%)1, generally small in size and only included a single species of common hard coral (Oulastrea crispata). The subtidal habitat was therefore considered as low ecological value. Nevertheless, as most of the coral colonies recorded in the Project area are attached on rocks and boulders and the recorded species is not competitive and aggressive in nature, they are considered as suitable for coral translocation. Coral translocation exercise has been successfully carried out in other part of Hong Kong water in the past2 and post-translocation monitoring showed that no adverse impacts on the transplanted coral were resulted from the translocation exercises.

7.2.4               In this Project, the assessment recommended to translocate the potential directly affected coral colonies attached on small rocks and boulders that are manually movable by a diver underwater (possibly longest dimension less than 50 cm) as far as practical to the nearby suitable habitats. To maximize the successfulness of this translocation exercise, the coral recipient sites should be as near as possible to the existing coral site and with similar healthy coral communities of the same species as well as similar hydrographic condition.  Three possible recipient sites are identified in the vicinity of the Project area (Kowloon Bay, Junk Bay and Clearwater Bay) and Junk Bay  is considered as the most suitable option and be suggested as marine waters of Kowloon Bay might be subjected to potential impact from future development including some marine works in the Kai Tak area while Clearwater Bay is considered too far away from the Project site when compared with Junk Bay.

7.2.5               A 20 m x 20 m coastal area at Junk Bay is proposed as a practical and feasible recipient site (Figure 7.1). Coral translocation to this proposed recipient site should not engage any permitting application under the Dumping at Sea Ordinance (Cap. 466) nor the Foreshore and Seabed (Reclamation) Ordinance (Cap. 127). In addition, this proposed recipient site is unleased and unallocated government land with no specific marine use and are therefore considered practically suitable for coral translocation. The proposed area (400 m2) of coral recipient site will provide sufficient space for proper placement of translocated coral colonies in the field based on the rough estimate of about 50 rocks / boulders with attached coral colonies (occupying the largest area of less than 0.25 m2 each) would be translocated to this recipient site. The translocation exercise should be conducted before the commencement of construction phase of the Project.

7.2.6               Translocation work should meet the following criteria in order to increase the effectiveness of this mitigation measure:

l               Proposed recipient site should compose of healthy coral communities of same species and similar hydrographic condition

l               The translocation process should be completed as quick as possible to minimize stress on transplanted corals during the transportation to recipient site

l               Coral colonies should be moved with lifting bags underwater and submerged in seawater with aeration onboard

l               Coral colonies should be transplanted at similar depth and orientation as the existing coral site

 

 

 

 

 

 


1.        Estimated percentage of coral cover area within 100 m x 2 m REA survey area according to the seven standard ranked categories in REA as specified in 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.

2.        Black & Veatch. (2005). Proposed Extension of Public Golf Course at Kau Sai Chau Island, Sai Kung EIA report.

7.2.7               General steps for the whole coral translocation exercise are suggested below and should be followed as far as practicable:

l             Locate a suitable recipient site for transplanted corals before commencement of coral translocation works;

l             Collect baseline information (e.g. total number of coral colonies to be translocated, health status, attached boulder size, etc.) of transplanted coral colonies in pre-translocation survey before commencement of coral translocation works;

l             Tag the transplanted coral colonies one by one in the pre-translocation survey;

l             Record the size, depth and orientation of each tagged coral colonies in the pre-translocation survey;

l             Move boulders with translocated coral colonies from sea bottom to ship/boat with lifting bag;

l             Submerge translocated coral colonies in large plastic bucket filled with seawater with aeration onboard;

l             Transport coral colonies to recipient site as quick as possible;

l             Place the transplanted coral colonies in the recipient site in similar depth and orientation as the existing coral site;

l             Record information (e.g. health status, translocated location of tagged coral, etc) of transplanted coral colonies upon the completion of translocation works; and

l             Carry out post-translocation monitoring on transplanted coral colonies every three months for a year after completion of coral translocation works.

 

7.2.8               A detailed translocation plan (including identification of recipient site, pre-translocation survey, translocation methodology, monitoring of transplanted corals, etc.) should be drafted during the detailed design stage of the Project.  The translocation plan should be proposed by the ET in agreement with the IEC and should be approved by AFCD prior to the commencement of coral translocation exercise and monitoring programme. All coral survey, translocation and monitoring exercises should be carried by qualified marine specialist who has suitable coral knowledge and sound experience in identifying corals in field situation, and to be approved by AFCD as well.

 

Measure for indirect coral impacts

 

7.2.9               During dredging operations, a number of mitigation measures to control water quality would be adopted to confine sediment plume within proposed dredging area and to minimize indirect impact to the nearby coral colonies outside the proposed dredging area. Recommended mitigation measures include the following:

l            Installation of silt curtains around the dredgers, where appropriate, during dredging activities.

l            Use of closed grab dredger.

7.2.10           With the implementation of these mitigation measures, no substantial changes in water quality, and only minimal ecological impacts on marine environment and associated wildlife would be resulted. The recorded coral species within the Project area is very common and widespread in Hong Kong marine waters and in view of its special tolerance to extreme environment such as turbid water, indirect impact of change of water quality on those existing coral colonies caused from the dredging works is expected to be minor and acceptable. 

 

7.3                    Coral monitoring requirement

7.3.1               Although adverse impact on coral colonies within the Project area was not predicted to occur after implementation of the suggested mitigation measures, post-translocation coral monitoring was proposed in the EIA report as an additional measure to verify the effectiveness of the suggested mitigation measures.

 

Pre-translocation Survey

7.3.2            Prior to the commencement of coral translocation, baseline survey of corals should be conducted within the hard substrata sea area within dredging site (Figure 7.2). All the potential directly impacted coral colonies should be tagged. For each tagged coral, specific detailed information should be collected including location, size, depth, attached rock/boulder size and general condition of their immediate surroundings. Tagged coral colonies should also be identified to the highest taxonomic resolution as far as 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.

7.3.3               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. Two categories of bleached area should be recorded:

l               Blanched (i.e. paled)

l               Bleached (i.e. bleached white)

7.3.4               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.

7.3.5               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.

 

Coral post-translocation monitoring

7.3.6            After translocation, the transplanted coral colonies should be regularly checked by qualified marine ecologist(s) to be approved by AFCD quarterly for one year after translocation. Dive surveys for post-translocation monitoring should collect the same information for tagged corals as the baseline survey. Information gathered during each post-translocation monitoring surveys should include observations on the presence, survival, and health conditions of the transplanted coral colonies. It should also include condition of the surrounding environment 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. Detailed monitoring proposal should be drafted during the detailed design phase of the Project and be approved by AFCD prior to the commencement of coral translocation.

7.3.7            All tags should be removed / retrieved after the monitoring programme is completed.

 

Reporting

7.3.8            A baseline survey report should be submitted to AFCD prior to the commencement of coral translocation exercise for reporting the results of the translocation exercise.

7.3.9            Post-translocation monitoring report should be submitted to AFCD within 2 weeks after the completion of coral translocation and each quarterly monitoring survey. The results of the post-translocation monitoring surveys should be reviewed with reference to the baseline survey results and findings of the condition of surrounding environment.