Solar radiation and its penetration in a tropical estuary

Abstract

The Cochin Backwater which is an estuarine area on the west coast of India receives maximum solar radiation from December to March and minimum from June to September. During the monsoon months the estuary becomes highly turbid as a result of the inflow of a considerable amount of fresh water. Seasonal changes in the attenuation coefficient showed that light penetration is small throughout the year and least during the monsoon months. No relationship was found between the attenuation coefficient and amount of suspended matter. The upward scattering of light in the estuary ranged from 2–8% of the incident illumination and the transmission of surface light at Secchi depth was about 23%. The compensation depth in the estuary varied from 2.5–5 m and the zone of optimum illumination for maximum photosynthesis lay between 0–1.5 m.