The change in copepod abundance and diversity possibly influenced by an anomalous China Coastal Current in the southern Taiwan Strait

Abstract

The cold China Coastal Current (CCC) flows southward into the Taiwan Strait from the East China Sea in winter, and is usually blocked by the warm Kuroshio Branch Current in the water west of Penghu. An unexpected intrusion of CCC to the surrounding waters of Penghu happened in February 2008. This intrusion of cold event caused a drop of 3.5 °C in water temperature at station A inside the Chinwan Bay of Penghu, as compared with the February 2006. We recognized 103 species of copepods belonging to 3 orders, 21 families, and 41 genera identified in this study. The first five dominant copepods during this study periods included Centropages tenuiremis, Paracalanus aculeatus, Oncaea venusta, Temora turbinata, and Clausocalanus furcatus. The cluster analysis showed that copepod compositions at the station inside the bay were significantly different from those at the stations outside the bay. The cold event due to the intrusion of the CCC clearly changed the copepod compositions at station A in the following two months. C. tenuiremis bloomed at station A in the month following this cold event. In the meantime the cold event did not seem to have apparent effect on the copepod compositions of the stations outside the bay. Copepod diversities were significantly lower at the station inside the bay than those of stations outside the bay, especially in March 2008.