Seasonal and diel vertical distributions of copepod assemblages in relation to environmental factors in Tapong Bay, southwestern Taiwan
| Autor: | Pei-Kai Hsu, 徐培凱 |
|---|---|
| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 The small-scale vertical migration patterns and spatiotemporal variations of copepods in the Tapong Bay, southwestern Taiwan, from 2003 to 2005 were studied. The differences in species composition and abundance of copepods before and after the removal of oyster culture racks in relation to tides, hydrography and other environmental factors were also compared and herein discussed. Tapong Bay has distinct dry (October to April) and wet (June to August) seasons and exhibits apparent inter-annual variation, cold, saline and low Chl a concentration in dry season, and vice versa in wet season. Most copepod species displayed normal diel vertical migration, descending to the deeper water during daytime and ascending to near surface water at night. Copepods were always more abundant at night than during daytime. Higher abundance but smaller species number of copepods were found during ebb than flood tides. In all, 123 copepod species belonging to 18 families and 31 genera were identified. Oithona oculata, Parvocalanus crassirostris, Acartia sinjiensis, Acartia sp., Bestiolina amoyensis and copepod nauplius were predominant and together they composed 74% of the total number of copepods. These dominant species showed apparent seasonal changes, with higher abundance in autumn and winter. Copepod assemblage also showed apparent difference between stations. Warm-saline-coastal species dominated in the outer region, while small-size taxa and common species of estuaries and aquaculture ponds dominated in the inner bay. Results of indicator species analysis could possibly recognize the area affected by tides and water masses, and identified Acrocalanus gracilis to be the indicator species of flood tide and outer region of the bay, and Acartia sinjiensis the indicator species of ebb tide and inner bay. Our results showed that after the removal of oyster culture racks the species number and abundance of copepods were higher but the seasonal and spatial differences in abundance became smaller. Furthermore, the increase in abundance of zooplankton and copepods in the Bay after the removal of oyster culture racks might be due to the absence of oyster population which exerts great filter–feeding impact on phytoplankton, and decrease of predation pressure from moon-jelly that usually aggregated in the inner Bay and settled down their polyps on the oyster racks but disappeared after the removal. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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