Impact of Environmental Factors on the Carbon Dynamics at Hooghly Estuarine Region

Degradation of litter from mangrove forests adjacent to the creeks at Sagar Island of the Hooghly-Matla estuarine ecosystem is one of the principal sources of nutrient to the estuary. This system receives a major load of carbon from adjacent mangrove forest in the form of litterfall throughout the year. Keeping in view, the effect of environmental factor on the dynamics of carbon is studied through multivariate statistics. Essential environmental variables like soil carbon, dissolved carbon, temperature, salinity, pH, and dissolved oxygen are analyzed following standard protocol. Multivariate statistical analyses like correlation, regression, and centered PCA ordination are done in order to know the impact of environmental variables on carbon dynamics. The results reflect a close intercorrelation among the studied environmental variables and carbon. It also emphasizes the fact that soil and water temperature, and dissolved oxygen affect soil carbon dynamics, whereas salinity and pH of soil and water greatly regulate dissolved carbon dynamics. The variance pattern of these studied variables through seasons is also enumerated by PCA ordination studies. 1. Introduction Out of the fourteen major rivers, the Ganges (2,525？km in length) along with its tributaries is the largest major river basin in India [1, 2]. It originates in the Gangotri glacier in the Himalayas in the state of Uttarakhand and its first deltaic offshoot is known as Hooghly estuary (21°31′–23°20′N and 87°45′–88°45′E). Sundarbans, vast lush green mangroves with distinctive faunal diversity, is located along the coastal line of Bay of Bengal, where the Ganges meets the sea (Figure 1). A wide variety of fishes harbour in the whole estuarine area and so the livelihood of the local people is mainly dependent on this ecosystem. Figure 1: Map of Hooghly estuary showing study site, Sagar Island. Construction of barrage at Farakka, port activity, dredging, and discharge of sewage hamper the normal activity of the estuary [3]. Primary production is controlled by the light availability that depends on the concentration of suspended particulate matter [4] and surface water remains undersaturated with respect to dissolved oxygen and production of large quantities of dissolved carbon dioxide also takes place in this estuary [5]. This estuary seems to be net heterotrophic ecosystem and the order of magnitude of the resulting atmospheric CO2 source has also been studied. Diurnal and seasonal variations, seasonal effects, and driving forces behind air water CO2 exchange are investigated [6, 7]. The