Zooplankton of the lagoons of the Laccadives: diel patterns and emergence

Abstract

Zooplankton populations in the water column increased substantially at night in four lagoons of the Laccadives. Epibenthic forms emerging into the water column during night, as well as non-epibenthic forms such as calanoid and cyclopoid copepods, were responsible for this. Unsealed traps were found subject to contamination and hence less reliable in estimating densities of emerging fauna compared with sealed traps. Direct sampling of the substratum during daytime showed that the actual densities of epibenthic forms are much higher than those observed in traps. Densities of emerging plankton varied geographically. Most of the zooplankton organisms which contribute to the lagoon fauna are resident in the lagoons and rarely occurred in the surrounding sea.