¨ the UN Biodiversity Treaty which includes the Indo-Pacific humpback dolphin (Chinese white dolphin; Sousa chinensis Osbeck, 1765) as a protected species; and
¨ the Convention on the International Trade in Endangered Species of Flora and Fauna (CITES) which lists Sousa chinensis in Appendix One.
¨ the Wild Animals Protection Ordinance (Cap. 170) 1980 which protects cetaceans;
¨ the Animals and Plants (Protection of Endangered Species) Ordinance (Cap. 187) 1988 which includes the protection of all stony corals, cetaceans and sea turtles;
¨ the Marine Parks Ordinance (Cap. 476) 1995 which applies to the marine park at Sha Chau and Lung Kwu Chau and limits certain activities in this area; and
¨ reference has also been made to Annexes 8 and 16 of the Technical Memorandum EIAO (Cap. 499) 1997 which sets out general criteria for evaluating the ecological importance of and hence the significance of potential ecological impacts and guidance for ecological assessment, respectively.
7.2.1 The proposed pipeline route passes through habitat utilised by Indo-Pacific Humpback dolphin. In addition, percussive piling for the jetty may have resulted in submarine noise that can be harmful to these marine mammals. Liu and Hills (1997) have stressed that in situations where an endangered species such as the Indo-Pacific Humpback dolphin is subjected to aggregated impacts, there is a strong case for a species-based ecological assessment which would seek an integrated and coordinated solution to predicting and mitigating potential impacts. For this reason, owing to the status and conservation importance of the dolphin, a species-based ecological assessment is required for the Indo-Pacific humpback dolphin. A location map showing the distribution of the key species of conservation concern and important ecological features in the study area is presented in Figure 6.2.
7.2.2 Construction of the pipeline and PAFF berthing jetty will not be approved unless it can be demonstrated that no unacceptable environmental impacts will result to the dolphins and other sensitive ecological receivers identified under this study. The ecological receivers potentially impacted by the PAFF (predominantly during the construction phase) comprise the following:
¨
benthic macro-invertebrate epifauna and infauna;
¨
corals;
¨
horseshoe crabs (Tachypleus
gigas, T. tridentatus and Carcinoscorpius
rotundicauda);
¨
Indo-Pacific Humpback dolphin (Sousa chinensis);
¨
artificial reefs (ARs) at Sha Chau; and
¨
Sha Chau and
¨ reference was made to Annexes 8 and 16 of the Technical Memorandum EIAO (Cap. 499) 1997 which sets out general criteria for evaluating the ecological importance of and hence the significance of potential impacts and guidance for ecological assessment, respectively;
¨ the assessment area included the Sha Chau and Lung Kwu Chau Marine Park and all areas within at least 500m from the project area including the pipeline alignment, areas with frequent vessel movement during the operational phase and any other areas further afield (i.e., at distances greater than the 500m required by the TMEIAO) potentially impacted by the project; and
¨
sites of conservation
importance and other ecological sensitive areas including the Sha Chau and
¨ review and collate the findings of other studies in the study area and other available information regarding the ecological characteristics;
¨ evaluation of the information collected and identification of any information gaps relating to the assessment of potential ecological impacts to the marine environment;
¨ establish the general ecological profile and describe the characteristics of each habitat found and major information shall include:
- description of the physical environment;
- ecological characteristics of each habitat type such as size, type, species present, dominant species found, species diversity and abundance, community structure, seasonality and inter-dependence of the habitats and species, and presence of any features of ecological importance;
- representative colour photographs of each habitat type and any important ecological features identified;
- investigate and describe the existing wildlife uses of various habitats with special attention to those habitats with conservation interest; and
- species found that are rare, endangered and/ or listed under local legislation, international conventions for conservation of wildlife or habitats or red data books.
¨ describe all recognised sites of conservation importance in the assessment area and describe how these sites will be affected by the proposed development;
¨ using suitable methodology, identify and quantify as far as possible, any direct, indirect, on-site, off-site, primary, secondary and cumulative ecological impacts such as destruction of habitats, reduction of species abundance or diversity, loss of feeding and breeding grounds, reduction of ecological carrying capacity and habitat fragmentation; with particular emphasis on the following:
- impact of habitat disturbance associated with dredging and backfilling of the pipeline route;
-
impact of habitat loss and
disturbance to wildlife arising from any works carried out in the Sha Chau and
- impact on hard and soft bottom assemblages as well as other marine organisms; and
- impacts upon resources of conservation importance during operations including spillage, maintenance as well as hazard risks (risk assessment of a fuel spill is presented in Section 11).
¨ assess the impact on the Indo-Pacific Humpback dolphin (Sousa chinensis) with particular emphasis on the following:
- review and incorporate the findings of relevant studies including the previous dolphin studies and collate the available information regarding the ecological characters of the assessment area;
- evaluate the information collected and identify any information gaps relating to the assessment of potential impacts on the dolphins;
- assess the impacts on the dolphin due to disturbance, loss of habitat and food supply;
- assess the cumulative impacts on the dolphins due to this project and any nearby dredging or reclamation works together with other existing or planned projects during construction;
- assess the disturbance of the dolphins habitat and the risk of the individuals being hit by vessel traffic in the vicinity of the facility during operation;
- identify precautionary and mitigation measures for protection of the dolphins. The proposed measures shall include those recommended in previous EIA and dolphin studies, such as ecological monitoring of the dolphins during the construction phase.
¨ evaluate the significance and acceptability of the ecological impacts identified using well defined criteria;
¨ recommend all possible alternatives and practicable mitigation measures to avoid, minimise and/ or compensate for the adverse ecological impacts identified with particular emphasis on the following:
- construction of the project at times that minimise impacts on the Indo-Pacific Humpback dolphin shall be considered, with the relative impacts of alternative schedules included; and
-
reinstatement of any habitats
in the Sha Cha and
¨ evaluate the feasibility and effectiveness of the recommended mitigation measures and define the scope, type, location, implementation arrangement, subsequent management and maintenance of such measures;
¨ determine and quantify the residual ecological impacts after implementation of the proposed mitigation measures;
¨
evaluate the severity and
acceptability of the residual ecological impacts using well-defined criteria;
and
¨
review the need for and
recommend any ecological monitoring programme, in particular on the
Indo-Pacific Humpback dolphin during the construction and operational phase.
7.4.1.1 A review of relevant scientific literature, reports and EIA’s has been conducted in order to assist the assessment of baseline ecological conditions. The study area comprising the Northwestern waters is arguably one of the most extensively surveyed marine locations in Hong Kong and reports from the ongoing environmental monitoring and audit conducted at the contaminated mud pits (CMP’s) at East of Sha Chau (Mouchel, 1996; 2001a; Meinhardt, 2006a) provided a large amount of the marine ecological information. As monitoring at the CMP’s is on-going, the data also represents relevant and recent ecological information for the study area.
7.4.1.2 For the purposes of the ecological baseline assessment, owing to the higher mobility of certain faunal groups (such as dolphins and horseshoe crabs), the relative homogenous nature of the sediments (and hence benthos) and hard rock substrata present, the study area described in the following sections encompasses records of marine species that have been observed throughout the Northwestern waters roughly covering an area from Sham Tseng in the east to Lung Kwu Chau in the west. These extensive data facilitate an improved description of the existing ecological conditions in the waters of the wider study area than is possible by focussing to only within 500m of the PAFF study area as stipulated in the TMEIAO. Such reasoning would appear to be appropriate for the evaluation of the marine environment as marine species are often relatively mobile (for example, their larval stages are dispersed over wide spatial areas) and are potentially capable of colonising suitable substrata over wide areas. It should be noted, however, that the available data for the Indo-Pacific Humpback dolphin is highly location-specific (owing to intensive survey effort) and it is possible to describe the species’ distribution in the Northwestern waters to a greater level of accuracy.
7.4.1.3 Relevant scientific reports and papers have also been reviewed and a full list of studies cited is provided in the References section of this chapter. The major scientific studies and reports include the following:
¨ New Airport Master Plan (Greiner-Maunsell, 1991);
¨ Proposed Aviation Fuel Receiving Facility at Sha Chau: Environmental Impact Assessment (ERM, 1995);
¨ Feasibility Study & Environmental Impact Assessment for Aviation Fuel Pipeline (Montgomery Watson, 1996);
¨
EIA Study for Disposal of
Contaminated Mud in the
¨ Feasibility Study for Additional Cross-border Links Stage 2 (Mouchel, 1998);
¨ EIA for the Proposed Sand Extraction from The Brothers’ Marine Borrow Area (Hyder Consulting, 1998);
¨ Population Biology of the Indo-Pacific Hump-backed Dolphin (Sousa chinensis Osbeck 1765) in Hong Kong Waters. AFCD-funded study conducted by Ocean Park Conservation Foundation (Jefferson, 1998; 2000a , 2005; Hung, 2005).
¨ Environmental Monitoring and Audit for Contaminated Mud Pit IV at East of Sha Chau (ERM, 1999; Mouchel, 2001a; Meinhardt, 2006a); and
¨
EA Study for Backfilling of
Marine Borrow Pits at North of the Brothers (Mouchel, 2002a).
7.4.1.4
The study area is located in
the Northwestern waters of
7.4.1.5 The study area is located within the Pearl River Estuary and is strongly influenced by freshwater discharges especially during the wet season when the summer monsoon brings high levels of precipitation (peak wet season discharge of 1,800 M m3 day-1; Broom and Ng, 1996). The western waters are, therefore, predominantly low in salinity and high in turbidity and show a marked seasonality.
7.4.2
Present Eco-Physical
Characteristics of the Study Area
7.4.2.1 There have been numerous assessments of the physical, chemical and biological environment conducted in the study area (Greiner-Maunsell, 1991; Binnie Consultants, 1995; Mouchel, 1996; ERM, 1997, 2005; Hyder Consultants, 1998; Meinhardt, 2006a). There have also been several past and ongoing studies conducted and notable are those involving investigations of Marine Borrow Areas and the ongoing monitoring at the Contaminated Mud Pits at East of Sha Chau conducted for the Civil Engineering and Development Department (CEDD). Several of these studies provide pertinent marine ecological baseline information for the current study and field visits have also been conducted to confirm that no natural intertidal habitat will be affected by the project. Then field survey data that form the basis of the assessment are presented in subsequent sections below and cover a duration of greater than the six months (wet season) required by the Study Brief. The PAFF tank farm is located on reclaimed land at Tuen Mun Area 38 and there is no natural coastal habitat that will be affected by the construction or operation of the project. The berthing jetty used by the tankers for fuel delivery is located 200m off-shore from Tuen Mun Area 38. The vertical seawall interfacing with the sea is shown in Plate 7.1.
7.4.2.2 The major conclusion from the previous work conducted in the study area is that the marine benthic environment in the western waters of Hong Kong are generally characterised by soft-bottom material composed of silts and clay as a homogenous layer or in loosely packed mud clasts bound in a puzzle fabric (Binnie Consultants, 1995; ERM, 1999; Mouchel, 2001a) although coarser material under the influence of strong tidal currents has been reported from the area to the Northeast of The Brothers (Greiner-Maunsell, 1991). There are also some hard substrates present although the soft-bottom sediments are characteristic of the study area. The upper sediment layers are reported to be well oxygenated (EVS, 1996) and typical images of the composition of the benthic sediments (and ecological characteristics present in both soft-bottom and hard substrate) are presented in Figure 7.1. The heterogeneity of sediments present in the study area provides a wide variety of niches although owing to the prevailing estuarine conditions that lead to fluctuations in physico-chemical parameters, it is nevertheless a ‘naturally stressed’ environment and this is reflected in the relatively low to moderate diversity of burrowing in-fauna present compared to other locations in Hong Kong (Shannon-Weiner index H’ typically < 2; Mouchel, 2001a; Meinhardt, 2006c).
7.4.2.3 Comprehensive ecological surveys were conducted at the North of The Brothers MBA and around Chek Lap Kok in 1990 as part of the new airport core construction EIA (Greiner-Maunsell, 1991). These data together with the past ten years of extensive monitoring data obtained during the contaminated mud pit (CMP) monitoring at East of Sha Chau collected from various stations in Northwestern waters (ERM, 2001; Mouchel, 2001a; Meinhardt, 2006c) are the most relevant to the current study. The findings from the two aforementioned studies have, therefore, formed the basis for much of the following discussion.
7.4.3
Present Pollution Status
7.4.3.1
The sediments in the
Northwestern waters have recently been assessed using a suite of measurements
to calculate a Pollution Index. The index is derived through chemical
contaminant analysis, assessment of the benthic macro-infauna present and
toxicity testing with a marine amphipod. Results indicated that the sediment
Pollution Index for Northwestern waters was average and similar to the majority
of other locations in Hong Kong with the exception of
7.4.3.2 Recently, further assessment of the pollution status of the marine sediments in the study area has been evaluated at stations located to the south of Sha Chau (between the airport and Sha Chau) using key biological indicator organisms (to facilitate the calculation of biotic indices) present in the benthic communities. Biotic indices are considered to be sensitive, easily-understood measures of pollution and provide a synoptic evaluation of both the prevailing sediment quality and overlying water chemistry thus adding further information on the benthic communities present in the study area. Biotic indices calculated for benthic macroinvertebrates collected at locations to the south of Sha Chau in May 2001 were indicative of slight pollution and an unbalanced benthic community (Mouchel, 2001a; Meinhardt, 2006c). A low biotic index is, however, often typical of estuaries owing to their highly dynamic physical and chemical nature and the benthic community diversity is also typically lower at these locations (Mouchel, 2001a; Meinhardt, 2006c).
7.4.4.1 The macro-infauna consist of the organisms larger than 1mm living within the sediment (predominantly in the upper well-oxygenated layers). The foregoing discussion on the benthic macro-infauna present throughout the study area comprises data reviewed from several benthic community studies (review mostly based on Greiner-Maunsell, 1991; Binnie Consultants, 1995; ERM, 2001; Mouchel, 2001a, 2002b; CCPC, 2002; Meinhardt, 2006c) and species present are relatively similar throughout the North-western waters (and other areas in Hong Kong) and are representative of the general study area. As indicated below in Section 7.4.4.2, the major difference in the faunal groups/species recorded both in different studies and between locations in Northwestern waters is the occasional absence of echinoderms although this is more likely to be a reflection of freshwater inputs from the Pearl River (the larvae of these organisms are stenohaline) driving the distribution pattern. The benthic community results presented are, therefore, considered to be representative of the study area.
7.4.4.2
The monitoring results in the
study area have tended to indicate that the benthic community recorded over
approximately the past ten years has remained of similar composition and as
with most benthic communities polychaetes are numerically abundant comprising
between 44-71% of individuals present and molluscs, crustaceans and echinoderms
are well represented components of the soft-bottom community (Binnie
Consultants, 1995). Echinoderms are, however, not always recorded in the study
area (Greiner-Maunsell, 1991) as the larvae of these organisms are often
stenohaline (Nicholson, 2001) and unlikely to tolerate the wide salinity
fluctuations associated with freshwater exposures from the
7.4.4.3 Results of benthic sampling (collected with a Van Veen grab) conducted in the study area in the late wet season in August 2000 resulted in the collection of 72 sediment samples containing 6,512 macro-infaunal specimens belonging to 84 families comprising 9 different phyla (ERM, 2001). In terms of dominant families present in the soft sediments, the annelids, arthropods and molluscs were dominant and the latter group also constituted most of the biomass present (see Table 7.1a). Recent results of sampling conducted in May 2001 resulted in the collection of 72 sediment samples containing 9,283 macro-infaunal specimens belonging to 67 families comprising 9 different phyla (Mouchel, 2001a; see Table 7.1b). The total recorded biomass in May 2001 was 188.85 g and was largely due to the high mass of annelids and molluscs collected (see Table 7.1b). The benthic survey data collected in the late wet season in August 2001 ((Mouchel 2002b)) showed that in terms of families present, the annelids, arthropods and molluscs were again the most dominant. These families also comprised the majority of individuals present. Compared to the monitoring conducted in August 2000, there were fewer families recorded in both May and August 2001 although the annelids, arthropods and molluscs were consistently the most dominant families recorded. Comparing data within the early and late wet season of the same year, there were both more families and individuals recorded during the late wet season in August compared with May 2001. There was also higher biomass recorded in August compared to the previous monitoring in May 2001. In May 2001 a total biomass (wet weight) of 188.85g was recorded whereas 662.07g was recorded in August 2001. The precise reasons for the recorded differences between the data collected in May and August 2001 are difficult to ascertain although they may represent differences in recruitment variation between the late dry/early wet (May) and late wet (August) season months (Table 7.1b).
Table 7.1a Summary of the Macro-infauna Collected in August 2000
|
Phylum |
Number
of Identified Families |
Total
Number of Individuals |
Total
Biomass (g) |
|
Annelida |
34 |
4,914 |
27.88 |
|
Arthropoda |
20 |
1,131 |
39.25 |
|
Chordata |
3 |
5 |
3.24 |
|
Coelenterata |
7 |
35 |
3.05 |
|
Echinodermata |
4 |
80 |
53.75 |
|
Echiura |
1 |
1 |
0.45 |
|
Mollusca |
14 |
301 |
847.72 |
|
Nemertinea |
0 |
19 |
1.51 |
|
Sipuncula |
1 |
26 |
0.11 |
|
Total |
84 |
6,512 |
976.97 |
Source: ERM (2001)
Table 7.1b Summary of the Macro-infauna Collected in May 2001
|
Phylum |
Number
of Identified Families |
Total
Number of Individuals |
Total
Biomass (g) |
|
Annelida |
30 |
2,204 |
45.609 |
|
Arthropoda |
13 |
405 |
26.526 |
|
Chordata |
2 |
2 |
2.352 |
|
Coelenterata |
4 |
13 |
1.329 |
|
Echinodermata |
2 |
15 |
0.723 |
|
Echinodetmata |
0 |
1 |
0.194 |
|
Mollusca |
11 |
6,600 |
95.562 |
|
Nemertea |
1 |
1 |
0.261 |
|
Sipuncula |
4 |
42 |
16.301 |
|
Total |
67 |
9,283 |
188.85 |
Table 7.1c Summary of the Macro-infauna Collected in August 2001
|
Phylum |
Number of Identified Families |
Total Number of Individuals |
Total Biomass (g) |
|
Annelida |
35 |
2,928 |
17.935 |
|
Arthropoda |
17 |
902 |
42.259 |
|
Chordata |
2 |
6 |
35.121 |
|
Coelenterata |
4 |
10 |
6.330 |
|
Echinodermata |
2 |
12 |
39.746 |
|
Mollusca |
10 |
9,4601 |
515.4731 |
|
Sipuncula |
2 |
18 |
5.208 |
|
Total |
72 |
13,336 |
662.07 |
Note: 1=
including Potamocorbula sp.
comprising 9390 individuals and biomass of 509.906 g.
Source: Mouchel (2002b)
7.4.4.4 The 2000/2001 data available for the study area comprising data collected over 12 months (wet season data only) showed that in terms of families present, the annelids, arthropods and molluscs were dominant. The annelids, molluscs and arthropods usually comprised the majority of individuals present. Although the number of families and biomass were lower than previously recorded in August 2000 there were a higher number of total individuals recorded in both May and August 2001 (Mouchel, 2001a, 2002b). During the sampling conducted in August 2000, 84 families and a total of 6,512 individuals were recorded for a total biomass of 976.9 g (ERM, 2001). The recorded differences between the data collected in August 2000 and the recent data collected in May and August 2001 may, however, represent seasonal variation between the late dry/ early wet and late wet season months inducing subtle changes to the benthic macro-infauna assemblages present.
7.4.4.5 However, the most recent data available are the surveys conducted in January and October 2005 (Mouchel, 2005a; Meinhardt, 2006b) covering both the dry and late wet seasons and the results are summarised in Table 7.1d below. The results were consistent with earlier surveys conducted under the EM&A programme. The annelids, molluscs and arthropods comprised the majority of individuals present and subtle seasonal variations, slightly higher abundance during the wet season, were frequently recorded.
Table 7.1d Summary of the Macro-infauna Collected in 2005
|
Phylum |
Number of
Identified Families |
Total Number of
Individuals |
Total Biomass
(g) |
|||
|
|
January |
October |
January |
October |
January |
October |
|
Annelida |
40 |
39 |
4,365 |
3,051 |
25.48 |
19.39 |
|
Arthropoda |
17 |
11 |
617 |
264 |
25.35 |
16.66 |
|
Chordata |
1 |
1 |
5 |
2 |
27.12 |
1.29 |
|
Coelenterata |
7 |
7 |
28 |
33 |
64.17 |
59.86 |
|
Echinodermata |
4 |
2 |
108 |
124 |
5.31 |
5.43 |
|
Echiura |
1 |
1 |
1 |
1 |
0.00 |
0.06 |
|
Mollusca |
10 |
12 |
164 |
70 |
171.92 |
81.75 |
|
Nemertinea |
- |
- |
- |
- |
0.57 |
0.03 |
|
Sipuncula |
1 |
2 |
43 |
67 |
0.31 |
23.01 |
|
Unidentified |
- |
- |
- |
- |
1.04 |
- |
|
Total |
81 |
75 |
5,331 |
3,612 |
321.26 |
207.48 |
Source: Mouchel (2005a) and Meinhardt (2006b).
7.4.4.6
High numbers of
macroinvertebrate infauna (67-81 families; Mouchel, 2001a; (Mouchel 2002b);
(Mouchel 2005a)) have been recorded in the study area. Abundance patterns in the Northwestern waters
appear to be reasonably similar to the macro-infauna recorded in the eastern
waters of
7.4.4.7 AFCD commenced a terrestrial-wide study on the marine benthic communities in Hong Kong in 2001 (CCPC, 2002) and concluded that in Hong Kong waters polychaetes, crustaceans and bivalves were the most abundant benthic fauna comprising over 70% of the total species. In terms of spatial pattern, it noted that the western waters, together with the north-eastern waters and Victoria Harbour showed distinct benthic composition as compared with the rest of the locations and the benthic species diversity and ecological importance of these three strata was generally lower. The estuarine conditions in the western waters largely accounted for the lower species diversity in the western waters.
7.4.4.8 Infauna diversity in the study area is relatively low (H’ < 2) compared to other areas in Hong Kong which is likely due to the proximity of Pearl River Estuary (estuarine areas are often less diverse owing to their highly dynamic physical and chemical nature) and possibly due to the predominantly silt-clay composition of the seabed that tends not to support high diversity (Shin, 1998; Mouchel, 2001a, 2002b).
7.4.5
Benthic Macro-Epifauna
Invertebrates
7.4.5.1
The macro-epifauna comprise the
larger organisms (typically > 1mm) that tend to live on or in close
association with the sediment surface. Trawl surveys were conducted within the
study area (at locations around
Table 7.2 Summary of Invertebrate Trawl Catch in the
Vicinity of Sha Chau (Jan-Dec 1995)
|
Phylum |
Class |
Common Name |
Number of Species |
|
Arthropoda |
Crustacea |
Crab |
19 |
|
|
|
Mantis shrimp |
1 |
|
|
|
Shrimp/ Prawn |
13 |
|
Cnidaria |
Anthozoa |
Gorgonian coral |
1 |
|
|
|
Sea anemone |
1 |
|
|
|
Sea pen |
4 |
|
Cnidaria |
Hydrozoa |
Hydroid |
1 |
|
Echinodermata |
Asteroidea |
Starfish |
1 |
|
|
Echinoidea |
Sea urchin |
1 |
|
|
Holothuroidea |
Sea cucumber |
1 |
|
|
Ophiuroidea |
Brittle star |
1 |
|
Mollusca |
Bivalvia |
Bivalve |
8 |
|
|
Cephalopoda |
Cuttlefish |
2 |
|
|
|
Octopus |
1 |
|
|
|
Squid |
1 |
|
|
Gastropoda |
Snail and sea slug |
10 |
|
Platyhelminthes |
Turbellaria |
Flatworm |
1 |
|
Total No. of Species |
|
|
67 |
Source: ERM (1997)
7.4.5.2 Data on the benthic macro-invertebrate epifaunal communities present are also available from demersal trawls conducted in the study area during May 2001 (early wet season) for the EM&A for the CMPs (Mouchel, 2001a). Six trawling stations were sampled, two of these located to the north and east of Lung Kwu Chau, two around the CMPs and two were also surveyed to the west of the airport. The trawling gear and methods were similar to those described above although five tows are conducted at each station and the cod end mesh was 2 cm in diameter. Trawling revealed that there were 113 invertebrate species present, see Table 7.3. As recorded previously, there were numerous mollusc and crustacean species present and fewer echinoderms. Thirty-five species of crab were recorded and these represented the most numerous group of epifaunal macro-invertebrates present. The epifaunal (demersal fish, crustaceans and gastropods) diversity recorded in the study area is low (H’< 2; Mouchel, 2001a) which may reflect both the naturally-occurring stressors such as periodic fluctuations in the physico-chemical environment associated with Pearl River run-off and anthropogenic impacts such as high trawling pressures.
Table 7.3 Summary of Invertebrate Trawl Catch in the Vicinity of Sha Chau Collected in May 2001
|
Phylum |
Class |
Common Name |
No. of Species |
|
Arthropoda |
Crustacea |
Crab |
35 |
|
|
|
Mantis shrimp |
6 |
|
|
|
Prawn or Shrimp |
23 |
|
Cnidaria |
Anthozoa |
Sea anemone |
1 |
|
|
|
Sea pen |
2 |
|
|
Scyphozoa |
Jellyfish |
1 |
|
Echinodermata |
Asteroidea |
Sea star |
1 |
|
|
Echinoidea |
Sea urchin |
1 |
|
|
Holothuroidea |
Sea cucumber |
3 |
|
Mollusca |
Bivalvia |
Bivalve |
12 |
|
|
Cephalopoda |
1 |
|
|
|
|
Octopus |
1 |
|
|
|
Squid |
2 |
|
|
Gastropoda |
Snails and sea slugs |
24 |
|
Total No. of Species |
|
|
113 |
Source: (Mouchel, 2001a)
7.4.5.3 However, more recent data on the benthic macro-invertebrate epifaunal communities present are also available from demersal trawls conducted in the study area during both the dry (January 2005) and late wet season (October 2005) in 2005 for the EM&A for the CMPs (Mouchel, 2005b; Meinhardt, 2006d). The results of the recent trawling, as presented in Table 7.4, were similar to those recorded in 2000/2001. As recorded previously, there were numerous mollusc and crustacean species present and fewer echinoderms. Thirty to thirty-two species of crab were recorded and these represented the most numerous group of epifaunal macro-invertebrates present. The epifaunal diversity recorded in the study area is low (H’< 2; Mouchel, 2005b; Meinhardt, 2006d).
Table 7.4 Summary of Invertebrate Trawl Catch in the Vicinity of Sha Chau Collected in 2005
|
Phylum |
Class |
Common Name |
No. of Species |
|
|
January |
October |
|||
|
Annelida |
Polychaete |
Polychaetes |
- |
1 |
|
Arthropoda |
Crustacea |
Crab |
30 |
32 |
|
|
|
Mantis shrimp |
5 |
6 |
|
|
|
Prawn or Shrimp |
17 |
14 |
|
Cnidaria |
Anthozoa |
Gorgonian coral |
1 |
1 |
|
|
|
Sea anemone |
1 |
1 |
|
|
|
Sea pen |
3 |
3 |
|
|
Scyphozoa |
Jellyfish |
1 |
1 |
|
Echinodermata |
Echinoidea |
Sea urchin |
2 |
1 |
|
|
Holothuroidea |
Sea cucumber |
3 |
3 |
|
Echiurid |
Echiuridae |
Echiurids |
1 |
- |
|
Mollusca |
Bivalvia |
Bivalve |
11 |
13 |
|
|
Cephalopoda |
Cuttlefish |
2 |
1 |
|
|
|
Octopus |
1 |
1 |
|
|
|
Squid |
1 |
1 |
|
|
Gastropoda |
Snails and sea slugs |
29 |
17 |
|
Total No. of Species |
108 |
96 |
||
Source: (Mouchel, 2005b; Meinhardt, 2006d)
7.4.6.1
There have been three species
of horseshoe crab recorded in Hong Kong coastal waters and although these
species are distributed throughout
7.4.6.2
Most of the horseshoe crabs
recorded in the Tuen Mun area have been previously identified as Tachypleus gigas (ERM, 1997; Chiu and
Morton, 1999). In an extensive study of the distribution of horseshoe crabs in
7.4.6.3
It has been suggested that the
horseshoe crabs show a seasonal trend in
7.4.6.4 Specimens of horseshoe crabs collected in the vicinity of the study area during March to September 1996 (ERM, 1997), records mostly from March 1995 to June 1998 (Chiu and Morton, 1999), September 2003 to May 2004 (Mouchel, 2004) and May 2001 to January 2005 (Mouchel, 2005b) are presented below in Table 7.5. The spatial distribution of horseshoe crabs in Northwestern waters is presented in Figure 6.2.
Table 7.5 Horseshoe Crab Sightings and Landings in the Study Area between June 1987 and January 2005
|
Location |
Species/ Remarks |
Date |
Number of
Individuals |
Biomass (g) |
|
Lung Kwu Chau |
Tachypleus gigas |
Jun, 1996 |
1 |
380 |
|
|
Tachypleus gigas |
Aug, 1996 |
1 |
325 |
|
|
Tachypleus sp. |
May, 2001 |
1 |
Not recorded |
|
|
Tachypleus tridentatus adult female |
Aug, 2001 |
1 |
Not recorded |
|
East of Sha Chau |
Carcinoscorpius rotundicauda adult |
Jul, 1995 |
1 |
Not recorded |
|
|
Tachypleus tridentatus juvenile |
Jan, 2004 |
1 |
Not recorded |
|
Lung Kwu |
Tachypleus tridentatus mating pair |
Jun, 1987 |
2 |
Not recorded |
|
Sheung Tan |
Tachypleus tridentatus adult |
Jun, 1905 |
1 |
Not recorded |
|
|
Tachypleus tridentatus mating pair |
May, 1995 |
2 |
Not recorded |
|
|
Unknown juvenile |
Mar, 1998 |
1 |
Not recorded |
|
Sha Lo Wan |
Unknown juvenile |
Apr, 1995 |
1 |
Not recorded |
|
Nim Wan |
Unknown juveniles |
May, 1995 |
8 |
Not recorded |
|
Tuen Mun |
Tachypleus tridentatus adult (dead) |
Jun, 1995 |
1 |
Not recorded |
|
The Brothers |
Unknown juvenile |
Apr, 1995 |
1 |
Not recorded |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
1667 |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
1667 |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
3636 |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
3030 |
|
|
Tachypleus gigas |
Jun, 1996 |
1 |
227 |
|
|
Tachypleus sp. |
May, 2001 |
1 |
Not recorded |
|
San Tau |
Unknown |
May, 1995 |
~ 13 |
Not recorded |
|
|
Tachypleus tridentatus and |
Oct, 1997- |
~ 15 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juveniles |
Jun, 1998 |
|
|
|
|
Tachypleus tridentatus 5 males, 6 females |
Apr, 1997 |
11 |
Not recorded |
|
|
Tachypleus tridentatus juveniles |
Jun, 2002 |
57 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juvenile |
Nov, 2003 |
1 |
Not recorded |
|
|
Tachypleus tridentatus juveniles |
Nov, 2003 |
10 |
Not recorded |
|
|
Tachypleus tridentatus |
May, 2004 |
11 |
Not recorded |
|
Tung Chung Wan |
Tachypleus tridentatus 5 males, 6 females |
Apr, 1997 |
11 |
Not recorded |
|
|
Carcinoscorpius rotundicauda |
Apr, 1997 |
1 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juveniles |
Jun, 2002 |
2 |
Not recorded |
|
|
Tachypleus tridentatus |
May, 2004 |
15 |
Not recorded |
|
|
Tachypleus tridentatus 13 males, 8 females |
Oct, 1997 |
21 |
Not recorded |
|
Hau Hok Wan |
Carcinoscorpius rotundicauda juvenile |
Nov, 2003 |
1 |
Not recorded |
|
|
Tachypleus tridentatus juveniles |
Nov, 2003 |
2 |
Not recorded |
|
Sham Wat |
Unknown juvenile |
Oct, 2003 |
> 10 |
Not recorded |
|
|
Tachypleus tridentatus |
Apr, 2004 |
1 and 3 molts |
Not recorded |
|
|
Carcinoscorpius rotundicauda |
Jan, 2005 |
1 |
189.4 |
|
Tai Ho Wan |
Unknown juvenile |
Sep, 1998 |
1 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juvenile |
Jun, 1999 |
8 |
Not recorded |
|
|
Carcinoscorpius rotundicauda mating pair |
Jun, 1999 |
2 |
Not recorded |
|
|
Tachypleus tridentatus |
Jun, 1999 |
2 |
Not recorded |
|
|
Carcinoscorpius rotundicauda juveniles |
Dec, 2003 |
20 |
Not recorded |
|
|
Carcinoscorpius rotundicauda |
May, 2004 |
14 and 3 molts |
Not recorded |
Note: Although Tachypleus gigas has
been reported in the wider study area, it may have been misidentified as Chiu
and Morton (1999) only recorded the similar Tachypleus tridentatus during
extensive surveys of the Northwestern waters. Adapted from AFCD (pers. comm.);
ERM (1997), Chiu and Morton (1999); Fong (1999); Huang (1997); Mott Connell Ltd
(2003); Mouchel (2004; 2005b).
7.4.7.1
Solitary corals have been
reported from the study area in the region around East Sha Chau and further to
the east at Sham Tseng and Tsing Lung Tau adjacent to
7.4.7.2
Corals are usually adversely
affected by reduced salinity (hyposalinity) and coupled to the high levels of
suspended solids discharged by the Pearl River (and hence low light
penetration) the absence of many hermatypic corals from the study area is not
unexpected. The coral communities of the study area are sparse compared to
rocky reefs of similar depth and exposure in the higher saline oceanic eastern
and southern waters of Hong Kong although a number of ahermatypic cup corals
(thought to be Balanophyllia or Phyllangia sp.), pale-blue gorgonian (Euplexaura sp.), Dendronephthya sp. colonies, isolated sea pens (Virgularia or Pteroides sp.) and one hermatypic coral Oulastrea crispata were recorded in June 2001 the far eastern
Northwest waters (at Sham Tseng and Tsing Lung Tau; Mouchel, 2001b; Figure
7.1). Similar results were also recorded
in dive surveys at Lung Kwu Chau in November 2001 (Maunsell, 2002). Coral dives survey conducted in Ocotber 2003
around along the tentative alignment for the HKZM Bridge recorded low abundance
(<5% cover) of one hard ahermatypic coral, Balanophyllia sp. on hard
substrate to the west of HKIA at Sham Wat/San Shek Wan, but not the eastern or
southern side (Mouchel, 2004). Low abundance (<5% cover) soft coral Echinomuricea
sp. was also recorded in the October 2003 survey at the eastern and
southern sides of the HKIA, but not the western side (Mouchel, 2004). It is
notable that the ahermatypic cup coral (Balanophyllia
or Phyllangia sp.) and the
pale-blue gorgonian (Euplexaura sp.)
have only rarely been recorded in the oceanic eastern and southern waters of
7.4.8
Cetaceans (Dolphins and
Porpoises)
7.4.8.1 There are sixteen recorded cetacean species from Hong Kong waters although only two of these species, the Indo-Pacific Humpback dolphin (Sousa chinensis) and Finless porpoise (Neophocaena phocaenoides) are resident (Parsons et al., 1995). Until the early 1990s there were few records of Sousa chinensis in Hong Kong waters (Jefferson and Leatherwood, 1997) although construction of the international airport at Chek Lap Kok drew attention to the presence of the Indo-Pacific Humpback dolphin in local waters and intensive research into the distribution and conservation requirements of the species have been ongoing since about the mid 1990s.
7.4.8.2 Although other cetaceans (Finless porpoise and False killer whale) have been found in the Northwestern waters, these are probably extralimmital records and only the Indo-Pacific Humpback dolphin has so far been consistently reported from the study area (comprising the area from Tuen Mun to the Southwest of the airport) where it is widely distributed (Parsons et al., 1995; Jefferson and Leatherwood, 1997; Jefferson, 2000a, 2005; Hung, 2005). There appears to be only limited overlap in distribution of the Indo-Pacific Humpback dolphin and Finless porpoise in local waters as the dolphin tends to be predominantly distributed in the western waters whereas the porpoise is usually recorded from areas further to the east of Hong Kong (the southern coast of Lantau around Fan Lau and the Soko Islands predominantly marks the western edge for the distribution of Neophocaena phocaenoides; Parsons et al., 1995; Jefferson, 2000a; Hung, 2005).
7.4.8.3
Globally, the Indo-Pacific
Humpback dolphin is widely distributed throughout shallow (< 20 m) coastal
waters of the Indian and
7.4.8.4
Groups of Indo-Pacific Humpback
dolphin are consistently recorded from waters near Tuen Mun and off Lung Kwu
Chau, Sha Chau and around HKIA although the distribution in Hong Kong may be
presently more restricted than when the population was assumed to contain more
individuals in the past (Parsons et al.,
1995). It should be noted, however, that no reliable census data are available
prior to the construction of the HKIA and the hypothesis that the population
was larger in the past is only an assumption.
The distribution of the dolphin tends to show a slight seasonal response
(possibly related to feeding opportunities, as the species is known to feed
predominantly on estuarine fish) as individuals tend to move further to the
east of the study area during the summer monsoon when ambient seawater is lower
in salinity (Jefferson, 2000a). In the dry season (winter and spring) the
population tends to be concentrated in the waters around the Sha Chau and
7.4.8.5 In addition, a six day baseline monitoring survey of Indo-Pacific Humpback dolphins in and around the project area was conducted in late 2005 using transects (Figure 7.3a) as part of the pre-construction dolphin abundance monitoring required by the previous Environmental Permit (EP-139/2002/A). Over the six days survey, the number of sightings per survey day varied between 3 to 11 and the group sizes ranged between 1 to 8, although 1 to 2 individuals were observed in the majority of the cases. The locations of the sightings recorded during the baseline survey are presented in Figure 7.3b and the original report is presented in Appendix F3.
7.4.9.1
The ecological value of each
habitat present in the study area is largely based on the species present. For
example, habitat that contains species of conservation interest or serve as a
nursery or breeding grounds are considered to have high ecological value. The
marine waters present in the study area are the media used by the species of
highest ecological importance, the Indo-Pacific Humpback dolphin. The waters within
the
7.4.9.2 Criteria for evaluating ecological impacts to habitats in the study area were determined in accordance with criteria stipulated in Table 2 (Annex 8) of the TM. The ecological value of both the soft and hard substrates present within the study area are discussed below in Sections 7.4.9.3-7.4.9.7.
Soft-Bottom Benthic and Littoral Habitat
7.4.9.3
The benthic habitats in the
western waters of Hong Kong are generally characterised by soft-bottom material
composed of silts and clay as a homogenous layer or in loosely packed mud
clasts bound in a puzzle fabric (Binnie Consultants, 1995; ERM, 1999) although
coarser material under the influence of strong tidal currents has been reported
from the area to the Northeast of The Brothers (Greiner-Maunsell, 1991). The
species present in the benthos are common and have been recorded in similar habitats
throughout
7.4.9.4 There is also the occasional sandy shore present in the study area, notably at Sha Chau. Previous surveys of the sandy shore at Sha Chau have however revealed that it is biologically depauperate. Similar findings were also recorded in the more recent field surveys conducted at Lung Kwu Chau (Maunsell, 2002). Extremely low species numbers and biological diversity are, however, typical of exposed sandy shores in the study area where the substrate is unstable (Morton and Morton, 1983; ERM, 1995).
Hard-bottom Benthic and Littoral Habitat
7.4.9.5 &