Vertical distribution of mesozooplankton biomass in relation to oxygen minimum layer in the Andaman Sea

Abstract

Mesozooplankton biomass in the upper 1000m of the Andaman Sea was studied
during February 1999 providing baseline information on stratification of
mesozooplankton of the area. The distribution of mesozooplankton biomass is
related to the oxygen minimum layer (<0.1 ml/litre). The biomass and group
wise diversity were maximum in the mixed layer (average 5 ml/100m3) and
sometimes in the thermocline layer (average 4.4 ml/1003). A prominent feature
was that the minimum average biomass values were confined to the depth strata
of 300m-bottom of thermocline (BT) (0.9ml/100m3) where the oxygen minimum
layer was more pronounced. The averages of zooplankton group percentages in
the upper 1000m showed that copepoda forms the major group (81.01 %) followed
by chaetognatha (6.7 %), ostracoda (4.8 %), siphonophora (1.9 %), and
decapod larvae (1.3 %) and the corresponding average population densities were
4,620 /100m3, 1,201/100 m3, 104/100 m3, 102 /100m3, and 7 /100m3.