Seasonal and tidal dynamics of nutrients and chlorophyll a in a tropical mangrove estuary, southeast coast of India

Abstract

Seasonal and tidal dynamics of dissolved nutrients (NH₄-N, NO₃+NO₂-N, PO₄-P and DOC), chlorophyll a, and primary production was studied in Pichavaram mangroves, Southeast coast of India. Seasonal changes showed an increase in salinity after tsunami (Pre-Tsunami; 24 ± 4.61, Post-Tsunami; 31 ± 2.35) due to the opening of sand bar at Coleroon River mouth causing an influx of seawater into the mangrove region at flood flow. However, dissolved nutrients showed no marked changes after tsunami and followed the seasonal pattern as observed prior to the event. There is an in situ regeneration of nutrients as a primary nutrient source rather than riverine input during a major part of the year. The nutrient balance of the Pichavaram mangroves was influenced by the tidal cycle. This is indicated by the changes in tidal height, salinity, inorganic nutrients, DOC and chlorophyll a over a 24 hours diurnal survey in both wet and dry seasons. The main features of the low tidewater were high concentrations of the nutrients showed the effects of tidal pumping mechanism. The tidal range were high after the December 2004 tsunami (Tidal range: Pre tsunami; 69±4.7, Post tsunami 126 ±11.8). It did not causes significant changes in the chemistry of the mangrove surrounding water column.