Abstract
Sagar Island in Indian Sundarbans is bestowed with numerous tidal creeks providing a suitable home to its inherent aquatic biota. The present study investigated the variation in the surface water quality in selected tidal creeks of Sagar Island, Indian Sundarbans to understand the present status of water quality for wildlife propagation and fisheries. Ten water parameters were taken into consideration for analysis on monthly basis from four stations (tidal creeks) from September 2015 to August 2016. One-way ANOVA showed five parameters (water temperature, salinity, dissolved oxygen, turbidity and chemical oxygen demand) varied significantly between seasons (p ≤ 0.05). Factor analysis exhibited four factors explaining 53.21% total variance in the observed data. Salinity and turbidity showed a maximum annual range of variations followed by dissolved oxygen. The fluctuations of physicochemical parameters throughout the year hinted toward the ever-changing nature of the estuarine ecosystem with possible human-induced impacts. Pronounced variation in turbidity seemed to be the effect of ferrying/transportation, monsoonal runoff and other human-induced activities. In the present study, water parameters viz., water temperature, dissolved oxygen and turbidity were the deterministic parameters influencing the variables in the system. The other important parameters were found to be COD, BOD3 and nitrate concentrations during the study period. The study shall provide baseline information in formulating the management measures in terms of water quality in wildlife propagation and fisheries.
Highlights
Sundarbans, the largest deltaic stretch of mangrove forest in the world, is formed at the estuarine phase of the Ganges— Brahmaputra river system (Chaudhuri et al 2012)
Dissolved oxygen and water temperature were influenced to a greater extent by atmospheric conditions and sampling times (Debels et al 2005); as a result, its concentrations vary during various moments of the day and under different weather conditions
Our observation is in conformity with Sarkar and Bhattacharya (2010) where the authors stated that dissolved oxygen concentration in the surface water of Sundarbans mangrove wetland ranged from 5.18 to 6.49 m gl−1 with an average value 4.0 mgl−1, indicating that surface waters are moderately oxygenated
Summary
Sundarbans, the largest deltaic stretch of mangrove forest in the world, is formed at the estuarine phase of the Ganges— Brahmaputra river system (Chaudhuri et al 2012). Tidal creeks are extremely abundant in Sundarbans estuarine systems which serve as feeder rivers, providing food control, storm water drainage and habitat to wildlife It is ecologically important for the transfer of materials from terrestrial to marine biome, habitat to nursery ground for. The large variability in hydrological parameters in coastal water influences, topographic heterogeneity and their interactions, has resulted in a biodiversity explosion in the Sundarbans mangrove eco-region (Ansari et al 2017). Such creek ecosystems are highly vulnerable to environmental changes and anthropogenic interferences, yet their ecological significance is underestimated as very less studies on these systems have been so far conducted relative to larger, better-known estuarine systems (Mallin and Lewitus 2004). The effects of climate change are well documented in and around Sagar Island (Mitra et al 2009)
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