Phytoplankton species composition, abundance and distribution in Fishing area 58 of Indian Ocean sector of Southern Ocean

Phytoplankton species composition, abundance and standing stocks investigations were carried out during the First Indian Antarctic Krill Expedition (FIKEX). Nitrate, phosphate and silicate were available in sufficiently higher concentrations at Polar Front zone. Nitrate and silicate, exhibited a marked boundaries between high values in the Sub Antarctic region. Diatom dominated the phytoplankton in the study region and their numbers generally increases southward with peaks of abundance in Sub Antarctic waters. Dinoflagellates, flagellates and “monads” occur in highest concentration north of the Polar Front zone. Various diatom assemblages are characteristics of different latitudinal zones. Vicinity of the Polar Front was found to be rich in Nitzschia, Pseudonitzschia group of species. South of Polar Front Nitzschia “nana” (Cells of both N. cylindrus and N. pseudonana) and Dactyliosolen tenuijunctus dominate. Diatoms viz. Fragilariopsis kerguelensis and Thalassionema nitzschioides ; were reported earlier and present studies. Present study laso reveals that the diatom Pseudonitzschia spp. were numerous in numbers.