7 MARINE
ECOLOGY.. 7-1
7.1 Introduction. 7-1
7.2 Mitigation
measures for corals. 7-1
7.3 Monitoring
requirement 7-2
7.1.1
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 dredging and reclamation works in the Victoria Harbour. In terms of ecological
importance, the assessment indicated that the affected habitats were generally
of very low ecological value and no adverse ecological impacts on marine
ecological resources are expected to occur.
7.1.2
Nevertheless, it is recommended to avoid direct loss or
damage of any species of conservation interest within the proposed reclamation
areas as far as possible. Translocation of all the existing coral colonies
found at the coastlines within ex-PCWA
Basin and along seawall
at North Point is recommended in the marine ecological impact assessment.
7.1.3
Other
indirect impacts on marine ecology arising from this Project are considered
temporary and minimal 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 adverse impact on marine life and other species of conservation interest
such as corals would not occur during the construction and operation of the
Project. Nevertheless, post-translocation coral monitoring is proposed as an
additional measure to verify the effectiveness of the coral translocation
measure.
7.2.1
Recent
dive surveys revealed that coral within subtidal habitat that would be directly
affected by the proposed reclamation works was low in species diversity (only
two species, Oulastrea
crispata and Echinomuricea sp.) and coverage (1 – 5%), with only small
colonies and common species recorded. The subtidal habitat was therefore
considered as low ecological value. Nevertheless, those 19 coral colonies
identified in recent survey were attached to small movable boulders and are practically feasible for
translocation. In addition, the recorded corals are
not competitive and aggressive species which are not expected to have any negative pressure on the other existing corals in the coral
translocation recipient site and are therefore considered suitable for
translocation. Coral translocation exercise has been successfully carried out in other
part of Hong Kong water in the past project (Black & Veatch, 2005,
Proposed Extension of Public Golf Course at Kau Sai Chau Island,
Sai Kung.) and post-translocation monitoring showed that no adverse impacts on the
transplanted coral were resulted from the translocation exercise.
7.2.1
In this Project, the assessment recommended to translocate all these
potentially affected coral colonies found at coastlines within ex-PCWA Basin (Site 13) and along seawall at
North Point (Site 27) (Figure 7.1 & 7.2) 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 assessment area (Victoria Harbour,
Junk Bay and Clearwater Bay) and Junk Bay is considered as the most suitable
option and be suggested as marine waters of the Victoria Harbour might be
subjected to potential impact from future development including some marine
works in the Central and Kai Tak areas while Clearwater Bay is considered too
far away from the Project site when compared with Junk Bay.
7.2.2
A 10 m x 10 m coastal area at Junk Bay
is proposed as a practical and feasible recipient site (Figure 7.3). 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 (100 m2) of coral recipient
site will provide sufficient space for proper placement of translocated coral
colonies in the field based on
rough estimate of about 20 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.
7.2.3
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.
7.2.4
A
detailed transplantation plan (including identification of recipient site,
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. Both coral translocation and monitoring exercise 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.
Baseline Survey
7.3.1
Prior
to the commencement of coral translocation, baseline survey of corals should be
conducted at the ex-PWCA
Basin (Site 13) and along
seawall at North Point (Site 27) (Figure 7.1 & 7.2). All the potentially affected
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.
7.3.2
Information
on health condition of the tagged corals should be recorded. For gorgonian
coral, the percentage of branches affected by partial mortality and secretion
of mucus should be recorded. For hard corals, health condition should include
information on surface area with partial mortality and blanched / bleached
area. Two categories of
bleached area should be recorded:
l
Blanched
(i.e. paled)
l
Bleached (i.e. bleached white)
7.3.3
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.
7.3.4
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 monitoring
after transplantation
7.3.5
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
transplantation. 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.
7.3.6
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.
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.
7.3.9
Post-translocation
monitoring report should be submitted to AFCD within 2 weeks after the
completion of coral translocation and each quarterly coral 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.