Spatial and temporal variability of copepod assemblages in Sanya Bay, northern South China Sea

Abstract

Sanya Bay, a tropical open coral-reef bay in the northern South China Sea, is undergoing great changes in environmental conditions due to the rapid increase in human activities. This study assessed spatial and temporal variation in copepod species composition, abundance, and distribution in relation to environmental variables in Sanya Bay. A total of 63 copepod species were identified. The annual average abundance of copepods was 4707.1± 2763.8 ind m–3, with the highest densities observed in winter and the lowest densities observed in summer. The number of copepod species increased from nearshore to offshore waters of the bay, whereas their abundance decreased seaward, with highest values being recorded in nearshore waters. Approximately 90% of copepod recorded in this study belonged to 11 dominant species.Parvocalanus crassirostriswas the most common and abundant species in Sanya Bay. Abundances of total copepods and P. crassirostris were negatively correlated with temperature and positively correlated with chlorophyll a concentration, but no significant correlation between them was found in spring, summer or fall. High abundances of copepods were mainly concentrated near the mouth of the Sanya River. The seasonal and regional patterns of copepod variation in Sanya Bay were characterized by low diversity and high abundance in winter, and by highest abundance in the nearshore waters during the four sampling periods. Copepod abundance distribution in winter was enhanced by low temperature and high chlorophyll aconcentration, and was driven by the dominant species P. crassirostris.