Anthropogenic pressures of various sources and magnitude bring about a lot of changes in the physicochemical characteristics, of the seagrass and mangrove ecosystems of the world. A study was conducted during the period Jan-December 2015 to elucidate the status of the physicochemical aspects indicating the healthiness of these ecosystems in Tuticorin coastal waters, which was threatened due to the impact of industrialisation over a while. Seawater, sediment and infaunal samples for quality parameters have been collected every month and analysed following the standard procedures.
Not much variation noticed in the air and water temperatures and pH between the two ecosystems. Except for the dissolved oxygen concentration, which was significantly higher in the seagrass ecosystem (p<0.01), elevated levels of most of the water quality parameters like GPP, chlorophyll, T.S.S, TDS, ammonia and nutrients like nitrite, phosphate and silicate were noticed at the mangrove ecosystems. The significant proportion of the sediment both in the mangrove and in the seagrass beds was constituted by fine sand followed by coarse sand, clay and silt. The fine sand and coarse sand proportions are significantly varied between stations (p<0.001). The percentage of organic matter, organic carbon and N2 were also comparatively higher in the mangrove beds. The benthic productivity was more or less similar to the same numbers of taxa (six groups each were noticed in the mangrove as well as seagrass beds). Bivalve was the major benthic group with a mean density of 21.7±5.38nos.m-2 at the mangrove beds whereas isopod constituted the dominant constituent with a mean density of 21.67±7.21nos.m-2 in the seagrass beds. The density of macrobenthos was higher in the seagrass ecosystem and varied between 1.34 and 3.87g.m-2. In general, the mangrove ecosystem which is under the influence of high saline water from neighbouring salt pans is more critical as evidenced by the abnormal water and sediment quality parameters.