Species diversity of chaetognaths along the equatorial region of the Indian ocean with comments on the community structure

Abstract

Chaetognath species from the Indian Ocean equatorial region, 5° N-5° S extending the entire breadth of the Ocean, were studied. Among the 14 species found in the collections, cosmopolitan and typical Indo-Pacific tropical species contributed much to the fauna. The common species showed a meridional distribution the western side and a zonal distribution along the eastern part of the equatorial region. Aggregates of large populations of major groups of zooplankton contributed to the maximum biomass values confined to the area west of 55°E. Biomass values, abundance of common chaetognath species and integrated values for phosphate showed positive correlation. Studies on the coexistence among the 13 major groups of zooplankton indicated widespread positive correlation between groups. Most significant correlation existed among chaetognath species did not indicate any widespread coexistence. Low values of diversity index suggested that the region covered was not rich with respect to the Chaetognath species. However, the western part showed high diversity.