Species composition and horizontal distribution of the appendicularian community in waters adjacent to the Kuroshio in winter^|^ndash;early spring

Abstract

Species composition and horizontal distribution of appendicularians were investigated in waters adjacent to the Kuroshio, south of Honshu in winter-early spring. Twenty-one species belonging to 5 genera were found and the species composition was characterized by a strong dominance of Oikopleura longicauda and occasional dense occur- rence of Fritillaria pellucida. Oikopleura longicauda was distributed rather uniformly throughout the study area while F. pellucida was usually only sparsely distributed, although it was sometimes found in dense concentrations at the sta- tions close to the Kuroshio axis. Occurrence of O. dioica, a well-studied neritic species, was limited to the stations with a relatively shallow bottom and its relative importance in terms of abundance was small. Generally, the appendicularian biomass was less than one tenth of the copepod biomass in carbon. Nevertheless, the role of appendicularians in terms of secondary production was estimated to be smaller but comparable in magnitude to that of copepods, 1.7-202.3 mgC m � 2 d � 1 in the former and 30.0-185.2 mgC m � 2 d � 1 in the latter, because of their higher somatic growth rates and house production. Clearance rate of appendicularians was also estimated to be comparable to copepods, 3.1-591.3 L m � 2 h � 1 in the former and 49.0-462.1 L m � 2 h � 1 in the latter, owing to their much higher weight specific clearance rates.