Summary of Abstract Submission

Abstract Submission No. IO50-09-0023PresentationPoster


H.B. Dalabehera*1, V.V.S.S. Sarma1, P. Sudharani1, D. Desai1, J.S. Patil1, A.C. Anil1

1 National Institute of Oceanography, India


Five thermal fronts and adjacent non-frontal zones have been sampled in the northeastern Arabian Sea during winter to examine variations in physical and chemical properties and their impact on biological processes. Frontal zone are relatively cooler (0.4 to 1.2oC), saltier (0.03 to 0.14) and nutrient rich compared to outside suggesting occurrence of intense vertical mixing within the front. Despite increase in nutrient in the fronts, higher phytoplankton biomass was not observed in all fronts sampled compared to outside suggesting that either delay in biological response or enhanced grazing pressure. The inverse relationship of biomass of phytoplankton and zooplankton indicates that the concentration of former was controlled by the grazing pressure. Relatively lower or equal phytoplankton biomass was noticed within compared to outside fronts at two regions where high fishing activity was noticed. Such low phytoplankton biomass was associated with high zooplankton biomass and fish production indicating that enhanced grazing decreased phytoplankton biomass. The potential fishing zone identified by remote sensing sea surface temperature and chlorophyll-a were not always associated with high fishing activity suggesting that age of front is important. Higher primary production and f-ratios were observed in all fronts sampled suggesting that about 6 to 20% of the more organic carbon exported to the twilight zone in the fronts than outside indicating that frontal zones sequester atmospheric carbon dioxide more efficiently.