Further studies of plankton ecosystems in the eastern Indian Ocean. VIII. Seasonal, diurnal, and latitudinal variations in abundance of Euthecosomata along the 110°E. meridian

Abstract

A number of tropical euthecosomes reached peak abundance in the northern tropical water mass between 9 and 20º s. during the south-east monsoon (May-September), with the maximum abundance north of 14º N. Creseis virgula, Hyalocylis striata, Diacria quadridentata and Cavolinia longirostris were typical of this water mass. A few species such as Limacina lesueuri, Styliola subula, Cuvierina columnella and Cavolinia inflexa reached their maximum abundance at other times of the year in the subtropical water mass (south of 20ºS.). Limacina bulimoides was at a maximum around 14ºS. during September-November and there was a second maximum around 23ºS. (in different months). Nocturnal increase in occurrence and abundance was observed in Limacina leseuri, L. helicina rangii, Clio pyramidata, C.p. lanceolata, Styliola subula, Cuvierina columnella, Diacria quadridentata and Cavolinia inflexa.