JOURNAL OF PLANKTON RESEARCH | VOLUME 12 | NUMBER 2 | PAGES 305-321 | 1990
© Oxford University Press
research-article |
Zooplankton, especially calanoid copepods, in the upper 1000 m of the south-east Arabian Sea
National Institute of Oceanography Dona Paula 403 004, Goa 1Regional Centre of NIO PB 1913, Cochin 682 018, India
Received on February 17, 1989; accepted on August 30, 1989 Abstract. Vertical distribution of zooplankton in the upper 1000 m was studied from the south-east Arabian Sea in order to determine the variations in zooplankton at different depths. The distribution and migration patterns of calanoid copepod species were given special attention. The mean zooplankton standing stock in the upper 1000 m was 2.1 g dry Wt m–2, of which 97.7% was concentrated in the upper 400 m. Herbivores were generally more abundant at all depths, but did not predominate. An increase in zooplankton at night occurred in the upper 200 m, as well as at the 600–1000 m stratum. The maximum diversity of calanoid copepods also coincided with these two depths. Based on vertical ranges, the calanoid copepod species were assigned to three groups: (i) species occurring predominantly in the epipelagic layer and forming the bulk of the calanoids; (ii) relatively sparser deeper living species confined below 200 m; and (iii) species occurring throughout the water column. Some amount of vertical niche separation among congeneric species was indicated. While some species showed active migration, a good number of species were non- migratory.