A study was carried out to understand the changes in the meroplankton produdion in the two adjoining seas, Gulf of Mannar (Site-I) and Palk Bay (Site-II). Fortnightly collections were made from tach station round the year. These two collection sites are closer to tach other but still varied in many physical oceanographic aspects. Numerical abundance of meroplankton were observed maximum during the month of November '93 (1,44,993 nosh3 at site I and 136,695 nos/m3 at site 11) and their minimum were recorded during the month of July '94 at the site I (8814 nos/m3 and May '94 at the site II (10,094 nos/m3). The meroplanktonic components include, nauplius, protozoea and mysis larvae of prawns such as Penrreus semisulcatus, P. merguiensis, P. indicus, P. monadon, zoea of branchyura, zoea of petrolisthes, zoea of Emerib, megalopa larvae, eggs, fish larvae, bivalves and gastropod larvae. The in-situ physicochemical variables such as pH, temperature, dissolved oxygen, salinity and electrical conductivity and nutrients like phosphate, nitrate and silicate were also estimated. The relationship between physicochemical variables and meroplankters is discussed.

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