Ecology of Indian estuaries: 8. Inorganic nutrients in the Ashtamudi Estuary

Abstract

Ashtamudi Backwater is the second largest estuarine system of the southwest coast of India. Surface and bottom waters from 52 stations covering the entire watershed from the lower reaches of the Kallada River to the mouth of estuary have been analysed. Data pertaining to temperature, salinity, transparency, pH, dissolved oxygen, phosphate-phosphorus, silicate-silicon, nitrate-nitrogen and nitrite-nitrogen are presented and discussed. Various sources of pollution, deposition and filling and their impact on the ecosystem are also discussed. All parameters exhibited wide spatial and zonal variations governed mainly by mixing, nature and intensity of water pollution and other human interferences. Results of the analyses are statistically compared. Phosphate-phosphorus and silicate-silicon are available throughout the watershed. Depletion of nitrate-nitrogen and nitrite-nitrogen has been observed in certain heavily polluted regions