博士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 101 / Hong Kong has a special marine environment that it ranges from estuarine in the west to oceanic in the east under the influence of Pearl River runoffs. Therefore, a significant different fish community was developed in the northwestern waters as compared with other regions. This fish community had experienced detrimental anthropogenic disturbances in the 1990s when the Airport Core Program commenced. Extensive coastal development projects, including mega-scale reclamation in the creation of the Chek Lap Kok International Airport, large volume of marine sand dredging, and a central contaminated mud dumping facility, were commenced within a short period of time. At the same time, this water body is still one of the major remaining living habitats of the Indo-Pacific Humpback Dolphin, both Hong Kong government and the government of the Guangdong Province of China established marine protected areas to mitigate the impacts and conserve the environment for the dolphins. The prohibition of fishing activities in the protected areas then became the ensuing mitigations to the fish community. To study how the fish community responded to these disturbances, the fish community was tracked for 12 years from the start of reclamation to 5 years after the establishment of the marine protected areas in terms of changes in community structure and health. Significant shifts in community structure, typified by 17 species, were revealed by multivariate analyses and community metrics. Dynamic factor analysis disclosed two underlying common trends among them and their significant correlations with the changes in water quality, area of seabed disturbance and area of marine protected areas. A time lag on detectable community changes was also revealed. During reclamation, the fish density was low and community health was poor. Large species disappeared leaving a community dominated by small, fast-growing and young to mature species. After completion of reclamation, some large and medium species returned but soon after the establishment of marine protected areas, medium-sized, fast-growing and young to mature species thrived on reduction of fishing pressure and filled the guilds rapidly. Therefore, even fish density and community health were improved after the mitigation, the original community structure was not restored.
The coastal development projects had caused chronic influences to the environmental settings as well. The creation of airport platform, the changes of seafloor topography due to the very deep mud pits, the modified land runoffs and new sewage discharge had developed hydrographical and hydrological heterogeneity in the northwestern waters. The prohibition of trawling activities in the marine protected area and the restricted areas of the airport and the central contaminated mud dumping facility had changed the pattern of seabed disturbances. Significant differences in the fish community (discriminated by 19 species) and megabenthic invertebrate community (discriminated by 36 taxa) between three stations over the northwestern waters were shown on multivariate analyses. However, no significant relation between the fish species and the environmental variables could be found by Canonical Corresponding Analysis. In contrast, omitting the three sporadic taxa, the relations of the several regular taxa with different parameters of water and sediment qualities, trawling intensity and topographic difference of sea floor were revealed significantly. All indicator taxa are suspension- or deposit-feeders. The concentration of food (primary production or suspended solids) in the water column; seabed disturbance; and the sedimentation regime which affected the sinking of food to seafloor and the compactness of the seabed played the important roles in shaping the megabenthic community. The first station, which was nearer to the Pearl River Estuary, had higher organic nitrogen and primary production, and no bottom trawling disturbance, was typified by bigger catches of a deposit-feeding sea cucumber. The second station, which was situated at the west the airport platform, having higher suspended solid concentration in the water column and frequent disturbance of trawling activities, was remarkably dominated by a very thick shelled filter-feeding gastropod. The last station, which was next to a deep mud pit and had no trawling disturbance at all, had a high proportion of suspension-feeding sea pens in the catch. The slowdown of the water flow over the deep burrow might favour the sedimentation of finer particles which composed the more compact seabed for the less motile to sessile animals. Although no significant relation between the spatial difference in fish community and the environmental heterogeneity was found, the spatial distributions of the benthic organisms can also influence its distribution pattern indirectly.
The above findings support that impacts of coastal developments on fish community in estuarine environment are also significant even fishes inhabiting there have higher mobility and adapted to a dynamic environment. Delayed community changes can happen, if their spawning or nursery habitats are impacted, because different species have different life history traits, some will response later than the others. Similarly, besides of the instantaneous impacts on megabenthic community by direct species removal or smothering during the construction, delayed changes in community structures are still possible if there is a change in the environment due to modifications on hydrologic and hydrographic regimes of the water body. The environmental heterogeneity developed after the creation of new land and deep burrows promotes the progressive change in dominance species in different environments.
| Identifer | oai:union.ndltd.org:TW/101NTOU5451024 |
| Date | January 2013 |
| Creators | Yin-Ki Tam, 譚燕琪 |
| Contributors | I-Hsun NI, Hsueh-Jung LU, 倪怡訓, 呂學榮 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 163 |
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