Rank-Abundance Allocations as a Tool to Analyze Planktonic Copepod Assemblages off the Danshuei River Estuary (Northern Taiwan)

Abstract

The planktonic copepod assemblages off the Danshuei River estuary, at the boundary of the East China Sea and the northeastern tip of the Taiwan Strait, were studied as a function of conductivity-temperature-depth (CTD) data obtained from the area from Oct. 1998 to July 2004. From seasonal copepod samples, 120 copepod species were identified off the Danshuei estuary during a 6-yr study period. In a methodical comparison, the rank-abundance (RA) was compared to quantitative estimates and diversity indices of copepods (i.e., the occurrence rate, mean abundance, Shannon-Wiener diversity index, and evenness and species richness index). The present study shows for the first time long-term patterns of planktonic copepod communities, thus demonstrating the usefulness of the RA tool in characterizing plankton bioindicator species to monitor environmental changes. A general model of species successions with season is exemplified by 1 coastal species that dominated the copepod communities during warm-water situations: Temora turbinata. Calanus sinicus was an indicator species belonging to relatively cold-water species transported from the Yellow Sea and East China Sea during the northeastern monsoon in winter.