ASSESSMENT OF SEAGRASS BEDS, ASSOCIATED FISH ASSEMBLAGES AND SOCIO-ECONOMICS OF NORTHERN PALK BAY, INDIA          

Seagrasses are the only flowering plants, living immersed in seawater and are capable of doing reproduction entirely underwater (den Hartog, 1970). Seagrass ecosystems constitute an essential part of marine habitats in continental shelf waters throughout the world, except polar regions. There are 60 described species of seagrasses worldwide, within 12 genera, and 4 families and orders (Short et al., 2001). Palk Bay, a shallow tropical water body is located between Sri Lanka and India. There are 14 species of seagrasses identified in this region (Kannan et al., 1999). They are distributed in a variety of habitat ranging from high intertidal to shallow sub-tidal soft bottoms, i.e. sandy bays, mud flats, lagoons and estuaries, where they often form extensive mono- and multispecific meadows (Huh and Kitting, 1985).  

           Seagrass meadows are among the most productive plant communities, providing habitat and food for a variety of marine organisms (Heck and Westone, 1977; McRoy and McMillan, 1977; Orth et al., 1984; Summerson and Peterson, 1984, Duarte and Chiscano, 1999). Due to the complex architecture of the leaf canopy in combination with the dense network of roots and rhizomes, the seagrass meadows may stabilize bottom sediments (Fonseca, 1989) and serve as effective hydrodynamic barriers, reducing wave energy and current velocity (Koch, 1996), thereby reducing turbidity (Bulthuis et al., 1984) and decreasing coastal erosion (Almasi et al., 1987). Further, seagrass meadows trap large amounts of nutrients and organic matter in the bottom sediment (Gacia et al., 1999). Seagrass depletion might be induced by natural events such as storms (Gallegos et al., 1992) or diseases (den Hartog, 1987). Seagrass loss, however, mainly occurs due to human impacts and the most general explanation to reduction of seagrass is excessive nutrient enrichment, i.e., eutrophication of coastal waters (Kemp et al., 1983; Orth and Moore, 1983; Tomasko et al., 1996; McGlathery, 2001). Effluent disposal (Larkum and West, 1990) and changes in land use pattern (Shepherd et al., 1989) are other important anthropogenic disturbances that threaten seagrass populations. Along the coast of Palk Bay region, coastal aquaculture ponds release their effluents directly into the Bay and seaweed culture is being carried out above the water column of seagrass meadows. Bomb fishing and shore seining and indiscriminate trawler operations throughout the Palk Bay region have been causing severe physical damage to seagrasses and reducing the diversity and assemblage of associated fauna. For more information, please contact marine_balaji@yahoo.com