Composition and distribution pattern of plankton communities in lagoon and offshore region of Kavaratti Atoll, Lakshadweep Archipelago, India

This paper summarizes the spatio-temporal variation of phytoplankton and zooplankton assemblages in Kavaratti lagoon and offshore water of Lakshadweep Archipelago, India. The objective of this study was to evaluate phytoplankton and zooplankton assemblage with responses to changing environmental conditions in Kavaratti lagoon and offshore water. Samples were collected and analysed during the pre-monsoon and post-monsoon season during 2016. During this period, in total, 69 species of zooplankton and 54 species of phytoplankton were identified. The population density of various groups of zooplankton found to be of the following order: Crustacea > Foraminifera > Porifera > Chaetognatha > Ciliophora > Appendicularia. Similarly, phytoplankton composed of the order of Bacillariophyceae > Dinophyceae > Chlorophyceae > Cyanophyceae. The highest population densities were recorded in the pre-monsoon period of the study. The lagoon region recorded the maximum plankton distribution than the offshore region. Crustaceans exhibit maximum diversity and richness in all the stations and seasons studied. Macrosetella gracilis (711 nos/m(3)) was the most dominant zooplankton species observed and which may be attributed to the availability of preferential food and favorable environmental conditions. There is a significant effect of water salinity on the population density of Daphnia magna (652 nos/m(3)) has been noticed during the pre-monsoon season of the study. Daphnia magna is well adapted to certain fluctuations, such as low oxygen conditions, high pH, wide ranges of salinity, and temperature. Among the phytoplankton, diatoms, such as Bellerochea malleus (20,160 nos/m(3)), Coscinodiscus gigas (1180 nos/m(3)), Eucampia zodiacus (880 nos/m(3)), and Rhizosolenia alata (2380 nos/m(3)), were dominant during the study. The Shannon-Wiener Diversity Index (0.183-2.587) for phytoplankton represents moderate level of pollution in the Kavaratti Island. The canonical correspondence analysis (CCA) confirms that the positive correlation of environmental parameters, such as water temperature, salinity, ammonia, nitrates, and silicates, on the distribution and assemblages of the plankton community.

Automated summary

This study evaluates the spatio-temporal variation of phytoplankton and zooplankton assemblages in Kavaratti lagoon and offshore water of Lakshadweep Archipelago. It was found that the highest diversity and abundance of plankton were recorded during the pre-monsoon season, with Crustacea being the most dominant group of zooplankton and Bacillariophyceae being the most prominent group of phytoplankton in the study area.