Faunal shift between two copepod congeners (Temora discaudata and T. turbinata) in the vicinity of two nuclear power plants in southern East China Sea: spatiotemporal patterns of population trajectories over a decade

Abstract

Differential tolerance of congeners with an overlapping ecological niche, to the anthropogenic activities leads to a faunal shift at spatiotemporal scales, which in turn provides an insight to the subtle changes happening in the abiotic environment. Aiming to asses the effects of influent and effluent waters of two Nuclear Power Plants (NPP-I and NPP-II), of northern Taiwan this study monitored the biography and population trajectories of two congeners of calanoid copepod, Temora discaudata and Temora turbinata from September, 1998 to April, 2009, comprising 44 sampling cruises in the southern East China Sea. The two Temora species occurred in >90% of the samples, showing differential trends of occurrence and abundance. The density of T. turbinata was higher than T. discaudata. The absolute and relative abundance of both of the Temora spp. increased significantly from inlet and outlet stations to seaward stations 500–1000 m away from land, beyond which there was a decline in density. The effects of month, season, year on abundance and occurrence of either Temora species were highly significant. The maximum and minimum abundance of T. discaudata was recorded in Aug, 1999 and March, 2000, respectively, where as those of T. turbinata was recorded in May, 2000 and March, 2000. The density, and occurrence frequency of either species showed a positive correlation with seawater temperature, but neither species showed a significant correlation with salinity. The areas around inlet and outlet stations record lower copepod density than unaffected stations. Our results point to a faunal shift within the congeners in coastal waters in the vicinity of both the NPPs. These results will be useful in assessing the ecological impact of discharge from NPPs, and in understanding the long-term population dynamics of Temora spp. which are believed to be invasive and cosmopolitan.