Effect of physico-chemical regimes and tropical cyclones on seasonal distribution of chlorophyll-a in the Chilika Lagoon, east coast of India

• Published in: Environmental monitoring and assessment Vol. 189; no. 4; p. 153
• Main Authors: Sahoo, Subhashree, Baliarsingh, S. K., Lotliker, Aneesh A., Pradhan, Umesh K., Thomas, C. S., Sahu, K.C.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.04.2017; Springer Nature B.V
• Subjects: Atmospheric Protection/Air Quality Control/Air Pollution; Bacillariophyceae; Bays; Biodiversity; Biogeochemistry; Biomass; Chlorophyll; Chlorophyll - analysis; Coasts; Cyclones; Cyclonic Storms; Diatoms; Dissolved oxygen; Earth and Environmental Science; Ecology; Ecotoxicology; Environment; Environmental Management; Environmental monitoring; Environmental Monitoring - methods; Environmental restoration; Fresh water; Fresh Water - analysis; India; Lagoons; Monitoring/Environmental Analysis; Nitrogen - analysis; Nitrogen dioxide; Nutrients; Phytoplankton; Phytoplankton - growth & development; Plankton; Pore size; Precipitation; River flow; Rivers; Salinity; Seasonal distribution; Seasons; Seawater - chemistry; Temperature; Tropical cyclones; Water quality; Wind; Phytoplankton; Nutrients; Lagoon; Tropical cyclone; Salinity
• ISSN: 0167-6369; 1573-2959
• DOI: 10.1007/s10661-017-5850-5

A comprehensive analysis on spatiotemporal variation in physico-chemical variables and their control on chlorophyll- a during 2013–14 was carried out in the Chilika Lagoon. Spatiotemporal variation in physico-chemical regimes significantly controlled the phytoplankton biomass of the lagoon. Further, precipitation-induced river/terrestrial freshwater influx and marine influence controlled the physico-chemical regimes of the Chilika Lagoon, such as nutrients (NH 4 + , NO 3 − , NO 2 − , PO 4 3− and Si(OH) 4 ), temperature, salinity, total suspended matter and dissolved oxygen. This study revealed significant effects of tropical cyclones Phailin (2013) and Hudhud (2014) on physico-chemical regimes and in turn the phytoplankton biomass of the lagoon. Although both cyclones Phailin (2013) and Hudhud (2014) were intense, Phailin (2013) had a greater impact on the Chilika Lagoon due to the proximity of its landfall. Heavy precipitation caused an influx of nutrient-rich freshwater, both during each cyclone’s passage, through rainfall, and after, through increased river flow and terrestrial run-off. The increase in nutrients, carried by the run-off, promoted phytoplankton growth, albeit in lag phase. In general, phytoplankton growth was controlled by nitrogenous nutrients. However, the addition of SiO 4 through terrigenous run-off fuelled preferential growth of diatoms. The salinity pattern (which can be considered a proxy for fresh and marine water influx) indicated injection of freshwater nutrients into the northern, southern and central sectors of the lagoon through riverine/terrestrial freshwater run-off; marine influx was restricted to the mouth of the lagoon. Present and past magnitudes of salinity and chlorophyll- a were also compared to better understand the pattern of variability. A significant change in salinity pattern was noticed after the opening of an artificial inlet, because of the resulting higher influx of marine water. The overall phytoplankton biomass (using chlorophyll- a concentration as a proxy) remained consistent in the lagoon pre- and post-restoration. Due to the wide range of salinity and temperature tolerance, diatoms remained dominant in both pre- and post-restoration periods, but the overall phytoplankton diversity increased after the artificial inlet was dredged.