Seasonal Succession of Planktonic Copepods in Bight Environments of Northeastern Taiwan

The seasonality and parameters of ocean waters have a significant influence on planktonic copepod species richness and diversity in various marine environments near and surrounding Taiwan. We conducted 6 sampling cruises in the bights of Shen-Aou Bay and Fan-Zai-Aou Bay to investigate seasonal variations in copepod communities in northeastern Taiwan from Oct. 2007 to Jan. 2009. The sample included 76 species of copepods belonging to 4 orders, 22 families, and 36 genera identified in these 2 bays in northeastern Taiwan. The most abundant species were Temora turbinata (with a relative abundance (RA) of 29.34%), Paracalanus pan/us (of 21.98%), Canthocalanus pauper (of 7.86%), Calanus sinicus (of 4.00%), and Acrocalanus gracilis (of 3.93%). A cluster analysis showed that the copepod communities of northeastern Taiwan fluctuated with season during the study period. Calanus sinicus showed a significant negative correlation with seawater temperature (r = -0.434, p = 0.008) and was abundant during the period when the China Coastal Current intruded into northeastern Taiwan, indicating that it is a temperate species. In contrast, the abundances of 7 copepod species (Acr. monachus, T. discaudata, Macrosetella gracilis, Corycaeus (Corycaeus) speciosus, Cor. (Farranula) concinna, Oncaea media, and Copilia mirabilis) showed significant positive correlations with seawater temperature, indicating that they are subtropical and tropical species. Copepod species, the community structure, and assemblages were distinguished by seasonality based on seawater temperature. Results suggest that the planktonic copepod communities in these 2 bays of northeastern Taiwan are primarily influenced by water temperatures, with seasonal succession determined by ingress of the China Coastal Current and Kuroshio Branch Current.