title: Effect of physico-chemical regimes and tropical cyclones on seasonal distribution of chlorophyll-a in the Chilika Lagoon, east coast of India.
abstract: 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 (NH4+, NO3-, NO2-, PO43-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 SiO4through 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.
authors.affiliation: Department of Marine Sciences, Berhampur University, Brahmapur, Odisha, 760 007, India.
authors.forename: Subhashree
authors.initials: S
authors.lastname: Sahoo
authors.affiliation: Indian National Centre for Ocean Information Services, Hyderabad, 500 090, India.
authors.forename: S K
authors.initials: SK
authors.lastname: Baliarsingh
authors.affiliation: Indian National Centre for Ocean Information Services, Hyderabad, 500 090, India. aneesh@incois.gov.in.
authors.forename: Aneesh A
authors.initials: AA
authors.lastname: Lotliker
authors.affiliation: CSIR-National Institute of Oceanography Regional Center, Mumbai, Maharashtra, 400053, India.
authors.forename: Umesh K
authors.initials: UK
authors.lastname: Pradhan
authors.affiliation: Science Systems and Applications, Inc., Ocean Biology Processing Group (OBPG), National Aeronautics and Space Administration (NASA), Goddard Space Flight Center (GSFC), Greenbelt, MD, 20771, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Thomas
authors.affiliation: Department of Marine Sciences, Berhampur University, Brahmapur, Odisha, 760 007, India.
authors.forename: K C
authors.initials: KC
authors.lastname: Sahu
mesh_terms: D061006:Bays; D018533:Biomass; D002734:Chlorophyll / Q000032:analysis*; D000077194:Chlorophyll A; D055867:Cyclonic Storms; D017377:Diatoms; D004784:Environmental Monitoring / Q000379:methods; D005618:Fresh Water / Q000032:analysis; D007194:India; D009584:Nitrogen / Q000032:analysis; D010839:Phytoplankton / Q000254:growth & development; D045483:Rivers; D054712:Salinity; D012621:Seasons; D012623:Seawater / Q000737:chemistry*; D013696:Temperature
chemical_list: D002734:Chlorophyll; D009584:Nitrogen; D000077194:Chlorophyll A
keywords: Lagoon; Nutrients; Phytoplankton; Salinity; Tropical cyclone