Hydrobiology of lagoons

Abstract

The hydrography, productivity, zooplankton biomass and faunistic composition of the lagoons of Lakshadweep were studied during January-March 1987 period. The surface temperature of lagoon waters off Agatti and Kalpeni reached the maximum temperature of 38"C. Even during night period the temperature was in the range of 32-33°C in the Minicoy lagoon. Salinity values of surface samples of lagoons of Kalpitti, Bangaram and Kalpeni mere in the range 36%o to 39.39%o. Low dissolved oxygen value of 1-1B ml/litre was observed in Suhelipar lagoon. In most of the lagoons the secondary production was very poor but biomass of zooplankton from the seaward side of the lagoons was slightly higher suggesting that the oceanic zooplankton might be nourished by coral reef community. Minicoy lagoon is an exception where the biomass of zooplankton was very high being 61.25 ml and the biomass of samples collected from the sea was 9.5 ml. Swarming 'of Lucifer sp, Copepods and Linglea sp. (algae) has increased the standing crop of lagoon. In most of the lagoons, decapod larvae and copepods constituted the dominant items, other zooplankter like fish eggi, chaetognaths, siphonophores and appendicularians also occurred In small numbers. In lagoon samples of Bangaram and Kavaratti fish eggs formed 8.73% and 17.38% of total biomass respectively.