International Journal of Biodiversity and Conservation Vol. 5(1), pp. 33-38, January 2013 Available online at http://www.academicjournals.org/IJBC DOI: 10.5897/IJBC12.092 ISSN 2141-243X ©2013 Academic Journals Full Length Research Paper Biodiversity of coastal Lagoon in Nallavadu village, Puducherry, India Anbarashan Padmavathy and Munisamy Anbarashan* Department of Ecology and Environmental Sciences, Pondicherry University, Kalapet, 605014, Puducherry, India. Accepted 4 January, 2013 The floristic and macro faunal diversity in Nallavadu lagoon (Puducherry, India) with an aerial length of 3.44 km was sampled monthly from June, 2009 to June, 2010. The lagoon salinity was 7.6 during post- monsoon period and 8.7 in pre-monsoon. Sequence of increased and decreased patterns in species diversity was noted during post-monsoon and pre-monsoon periods. Final results revealed, a total of 21 flora species (17 families) comprising of mangrove associates and in fauna, a total of 56 species (36 families) including 12 species of fishes, 9 species of gastropods, 6 species of bivalves, 9 species of crabs, 5 species of prawns, 3 species of snakes and 12 species of birds were recorded. This study was an attempt to provide a more complete inventory of the flora and fauna diversity of this coastal lagoon along the Puducherry coast. Key words: Coastal lagoon, fauna, molluscs, crustaceans, fishes, water snakes, conservation. INTRODUCTION Coastal lagoons constitute merely 13% of global coastline (Farmworth and Golley, 1974; Poyyamoli et al., 2010) and considered as a different coastal environment from estuaries (Kjerfve, 1994). Coastal lagoons notably act on the control of freshwater inflow and connections with the sea (Crivelli and Ximenes, 1992; Peja et al., 1996; Quinn et al., 1999), they are found to be highly dynamic, productive and extremely unpredictable systems (Barnes, 1980). Coastal Lagoons are shallow coastal bodies of water separated from the ocean or sea by a series of barrier islands, sand and sand bars, which lie parallel to the shoreline (Phleger, 1969). Coastal lagoons are formed and maintained through sediment transport processes. Sediment carried by rivers, waves, currents, wind and tides (Nichols and Boon, 1994) accumulates in river and tidal deltas, on marshes and flats where submerged aquatic vegetation slows currents, and on wash over fans. The process of sedimentation can eventually fill in lagoons (Nichols and Boon, 1994). Lagoon barriers are constantly eroded by waves and wind, requiring continuous sediment *Corresponding author. E-mail: anbupu@gmail.com. deposition to maintain them (Bird, 1994). Water quantity and quality in a lagoon is influenced by the rate at which the lagoon loses or gains water from evaporation, precipitation, groundwater input, surface runoff, and exchange with the ocean (Allen et al., 1981). Lagoon- ocean exchange is driven by tides and wave action (Zimmerman, 1981) and is often the largest component of lagoon water balance (Smith, 1994). Heat is also lost and gained through exchange with the atmosphere, sediment, and ocean (Smith, 1994). Their interface position between continental and marine ecosystems results in variability in its physical and chemical conditions. This extreme physio-chemical characteristic implying natural stresses over flora and fauna communities (micro and macro) in that lagoon systems (Anthony et al., 2009). Coastal lagoons contribute to the overall productivity of coastal waters. The vegetation is dominated by salt marshes, sea grasses, seaweeds and mangroves species, which can tolerate high soil and water salinities and waterlogging or periodic inundation (Mitsch and Gosselink, 1993). These species can enhance the biodiversity of a lagoon by providing a physical refuge from predation and also serve as nursery and feeding habitats for a variety of organisms (Heck and Thoman, 1984; Harris et al., 2004). Nutrients are transported to