Plankton production associated with cold water incursion into the estuarine environment

Abstract

Phytoplankton blooms comprising mainly of diatoms and dinoflagellates (approx. 0.55 million cell/l) and intense zooplankton swarms (biomass approx. 5.34 ml/m@u3@@) were observed in the Mandovi and Zuari estuarine environment in October-November 1980. During the period, pigment concentrations varied from 1.0 to 10.2 mg/m@u3@@. Temperature, dissolved oxygen and salinity at the upper layers showed variations from 26.77 to 30.15 degrees C, 4.7 to 5.8 ml/l and 27.25 to 34.4 ppt respectively. The nutrients such as NO@d2@@-N (0.35-1.4 mu g at/l) and PO@d4@@-P (1.4-2.8 mu g at/l) were high, whereas NO@d3@@-N was low (0.23-0.92 mu g at/l). At the subsurface layers temperature, dissolved oxygen and salinity varied from 22.5 to 29.16 degrees C, 0.6 to 56 ml/l and 32.7 ppt respectively. The variation of NO@d3@@-N was from 0.23 to 1.15 mu g at/l. NO@d2@@-N from 0.37 to 3.34 mu g at/l and PO@d4@@ -P from 1.43 to 4.45 mu g at/l. The incursion of cold, nutrient-rich subsurface waters into the euphotic region augmented the plankton production of the Mandovi and Zuari estuarine environment