Monsoonal Floods Affecting Cochin Backwater Ecosystem

The samples were collected in five sampling campaigns conducted during postmonsoon 2008, premonsoon 2009, monsoon 2009, postmonsoon 2009 and premonsoon 2010. The phytoplankton species dominant in premonsoon were mainly species of Chorella, Asterionella, Ceratium, Coscinodiscus, Nitzschia and Trichodesmium. During monsoon, species of Arthodesmus, Chaetoceros, Closterium, Dinorhysis and Spirogyra were abundant. Species of Volvox, Closterium, Peridinium and Ceratium were mostly represented. Copepods the main secondary producers were represented by species belonging to Acartia, Pseudodiaptomus, Paracalanus, Oithona and Coryceus. Copepods have indicated increase in carnivorous species namely Tortanus, Oithona, Oncaea and Corycaeus spp. The main fish species studied were Oreochromis mossambicus, Mugil cephalus, Channa striatus and Etroplus suratensis. Enumeration of the fish species in 2008 reported only 50 species as against 160 species observed in 1970’s. The changes in hydrochemical properties indicate environmental degradation with the increase of nutrient load. Eutrophication and harmful algal blooms are also observed. The recent reports of octopus in the fishing nets operating in the backwater suggest that salinity of backwater is on par with that of the Arabian Sea during premonsoon period. There is marked alteration in the predator components in the coastal fishery showing a significant rise in puffer fish. Recently, scientists from Central Marine Research Institute have spotted many dolphins in the CBW. Climate change and temperature rise in coastal waters cause damage to marine, estuarine and inland fishes. Vulnerability of plankton and fish in CBW exposed to floods and salinity ingress is causing serious threat to many traditional species.