PJB-2023-571
NUTRIENT DYNAMICS IN MANGROVE ECOSYSTEM IS A FUNCTION OF LITTER PRODUCTION AND DECOMPOSITION AT SANDSPIT BACKWATER KARACHI, PAKISTAN
Seema Shafique
Abstract
The importance of mangrove litter for food of a variety of organisms is well established. Litter production and decomposition has been studied previously from two locations in Pakistan. This communication presents release of dissolved nutrients in mangrove channel water at Sandspit. Overall concentration of nutrient ions was high during post-monsoon season. Highest values of all nutrients (NH4 15.41µg. l-1, NO3 8.26 µg. l-1 and NO2 6.58 µg. l-1), except for phosphates, were recorded in November. Phosphate had highest value (14.78 µg. l-1) in December. The levels of all nutrients showed sharp decreases and attained lowest values in summer. The in situ seasonal values of nutrient ions had significant correlation with the litter production in the area. The litter trap data reveals high production of litter during dry post-monsoon season (1.93±1.15 g.m-2.d-1) which is largely constituted of leaf litter (52%). Similarly, the in vitro leaf decomposition experiment clearly demonstrate release of particulate and dissolved matter during decomposition and 50% weight loss was noted in 48 and 50 days under aerobic and micro-aerobic conditions, respectively. Rate of release of all nutrient ions was slightly slower under micro-aerobic condition. Seasonal variability observed in water parameters and dissolved nutrients showed significant correlation with the litter production and decomposition. It is evident from the data that nutrient concentration in mangrove ecosystem (Manora Channel) is regulated through mangrove detrital system, though some influence of Layari River may exist. The organic detritus and nutrients could potentially enrich the coastal waters and ultimately support primary and secondary productivity.
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