Background: Comparing meiofaunal assemblages in the seagrass zone with bare sediment will provide information on the structuring factors and phytal preferences of meiobenthic invertebrates since differences in density and diversity of meiofauna are to be expected between vegetated and bare zones. Results: A total of 11 groups of meiofauna, with harpacticoids dominating (51 %) and comprising 48 species within 14 families, have been identified. At all localities, the following harpacticoids were found to be relatively abundant, contributing 30.9 % of all harpacticoids: Longipedia weberi, Canuellina nicobaris, Scottolana longipes, and Parastenhelia hornelli. A highly significant correlation (r = 0.987, r 2 = 0.974, F (1,9) = 337.3, P < 0.001) of meiofaunal assemblage was found between seagrass leaf blades and the canopy sediment compared to bare sediment which was found to have a moderate correlation (r = 0.543, r 2 = 0.294, F (1,9) = 3.756, P = 0.085). In addition, the abundance of harpacticoids was significantly higher (ANOVA, F (2,144) = 19.53, P < 0.001) in seagrass sediments and differed markedly from blades and bare sediments, and the composition was unique in the different zones of the present study. Conclusions: Productive seagrass ecosystems are as yet inadequately studied in the Andaman Islands. This study provides a first step to characterize a faunal group from the seagrass community.

BackgroundMicrozooplankton consisting of protists and metazoa <200 μm. It displays unique feeding mechanisms and behaviours that allow them to graze cells up to five times their own volume. They can grow at rates which equal or exceed prey growth and can serve as a viable food source for metazoans. Moreover, they are individually inconspicuous, their recognition as significant consumers of oceanic primary production. The microzooplankton can be the dominant consumers of phytoplankton production in both oligo- and eutrophic regions of the ocean and are capable of consuming >100% of primary production.ResultsThe microzooplankton of the South Andaman Sea were investigated during September 2011 to January 2012. A total of 44 species belong to 19 genera were recorded in this study. Tintinnids made larger contribution to the total abundance (34%) followed in order by dinoflagellates (24%), ciliates (20%) and copepod nauplii (18%). Foraminifera were numerically less (4%). Tintinnids were represented by 20 species belong to 13 genera, Heterotrophic dinoflagellates were represented by 17 species belong to 3 genera and Ciliates comprised 5 species belong to 3 genera. Eutintinus tineus, Tintinnopsis cylindrical, T. incertum, Protoperidinium divergens, Lomaniella oviformes, Strombidium minimum were the most prevalent microzooplankton. Standing stock of tintinnids ranged from 30–80 cells.L-1 and showed a reverse distribution with the distribution of chlorophyll a relatively higher species diversity and equitability was found in polluted harbour areas.ConclusionsThe change of environmental variability affects the species composition and abundance of microzooplankton varied spatially and temporarily. The observations clearly demonstrated that the harbor area differed considerably from other area in terms of species present and phytoplankton biomass. Further, the phytoplankton abundance is showed to be strongly influenced by tintinnid with respect to the relationship of prey–predator. Consequently, further investigation on microzooplankton grazing would shed light on food web dynamics.

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