Seasonal variations in species composition, abundance, biomass and estimated production rates of tintinnids at tropical estuarine and mangrove waters, Parangipettai, southeast coast of India

Seasonal varaitions in species composition, abundance, biomass and production rates of tintinnids (Protozoa: Ciliata) were investigated in the tropical estuarine and mangrove systems of Parangipettai, South India, monthly from January to December 1994. There were remarkable seasonal variations in environmental parameters, chlorophyll a concentrations and abundance, biomass and production rates of tintinnids: highest in postmosoon/summer and lowest in monsoon. The total abundance and biomass of tintinnids were in the range of 2-420 indiv. l(-1) and 0.02 3.01 mug C l(-1), respectively, with the peak appearing in the estuarine waters. A total of 47 species of tintinnids belonging to 14 genera was identified. Of which, Tintinnopsis was the most abundant genus in terms of number of species (20), followed by Codonellopsis (4), Stenosemella (4), Favella (3), Eutintinnus (3), and the remaining genus, number of species are one or two. Most of the tintinnid species occurred on distinct seasonal pattern and closely associated to species-specific environmental conditions. Due to large thermal gradients (range: 22.5-33.8 degreesC), the overall mean biomass was highest (mean: 1.64 mug C l(-1)) during summer than the remaining seasons. Estimated production rates of tintinnids ranged from 0.02 to 2.5 mug C I-1 day(-1), with peak in summer. The trophodynamic role of tintinnids was assessed by estimating their grazing impact as expressed by daily removal of phytoplankton biomass. The grazing impact also demonstrated a seasonal pattern and ranged from 0.03% to 1.24% removal day(-1). The higher grazing impact estimated during summer could be related to high concentrations of food supply. Due to significant positive relationship between the total biomass of tintinnids and chlorophyll a concentrations, food supply is not a problem for tintinnids harboring in this estuarine and mangrove systems. Hence, predation loss by meso- and macrozooplankton might be the possible reasons for the estimated low biomass of tintinnids in the present study. Therefore, the results demonstrate that tintinnids play an important role to transfer the production of pico- and nanoplankton to meso- and macrometazoan predators. Thus, the seasonal environmental factors exert major influence on the species composition, abundance, biomass and production rates of tintinnids. (C) 2002 Elsevier Science B.V. All rights reserved.