Time series monitoring of water quality and microalgal diversity in a tropical bay under intense anthropogenic interference (SW coast of the Bay of Bengal, India)

• Published in: Environmental impact assessment review Vol. 55; pp. 169 - 181
• Main Authors: Shaik, Aziz ur Rahman, Biswas, Haimanti, Reddy, N.P.C., Srinivasa Rao, V., Bharathi, M.D., Subbaiah, Ch.V.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-11-2015
• Subjects: Bay of Bengal; BAYS; BIOCHEMICAL OXYGEN DEMAND; Biological; Coastal water; Diatom; DIATOMS; DISSOLVED GASES; ECOLOGICAL CONCENTRATION; ENVIRONMENTAL SCIENCES; FERTILIZER INDUSTRY; Freshwater; Health; INDIA; Kakinada Bay; MANGROVES; N:Si ratios; Nutrient loading; NUTRIENTS; Oxygen demand; PHC; PHYTOPLANKTON; Phytoplankton bloom; RIVERS; SHORES; Skeletonema costatum; Thalassionema nitzschioides; Thalassiosira decipiens; Thalassiothrix frauenfeldii; Time series; TSM; WATER QUALITY; ISW, Bangladesh, Bengal Bay; Bay of Bengal; ISW, India, Andhra Pradesh, East Godavari Dist., Kakinada Bay; Kakinada Bay; Phytoplankton bloom; Nutrient loading; Bay of Bengal; Diatom; Skeletonema costatum; PHC; N:Si ratios; TSM
• ISSN: 0195-9255; 1873-6432
• DOI: 10.1016/j.eiar.2015.08.005

In recent decades, material fluxes to coastal waters from various land based anthropogenic activities have significantly been enhanced around the globe which can considerably impact the coastal water quality and ecosystem health. Hence, there is a critical need to understand the links between anthropogenic activities in watersheds and its health. Kakinada Bay is situated at the SW part of the Bay of Bengal, near to the second largest mangrove cover in India with several fertilizer industries along its bank and could be highly vulnerable to different types of pollutants. However, virtually, no data is available so far reporting its physicochemical status and microalgal diversity at this bay. In order to fill this gap, we conducted three time series observations at a fixed station during January, December and June 2012, at this bay measuring more than 15 physical, chemical and biological parameters in every 3h over a period of 36h in both surface (0m) and subsurface (4.5m) waters. Our results clearly depict a strong seasonality between three sampling months; however, any abnormal values of nutrients, biological oxygen demand or dissolved oxygen level was not observed. A Skeletonema costatum bloom was observed in December which was probably influenced by low saline, high turbid and high Si input through the river discharge. Otherwise, smaller diatoms like Thalassiosira decipiens, Thalassiothrix frauenfeldii, and Thalassionema nitzschioides dominated the bay. It is likely that the material loading can be high at the point sources due to intense anthropogenic activities, however, gets diluted with biological, chemical and physical processes in the offshore waters.
•No signature of enormous nutrient loading was observed over the diel cycle•Dissolved oxygen and BOD concentrations did not show any exceptional trend•Diatoms dominated more than 90% of the total phytoplankton communities•A Skeletonema Costatum (a centric diatom) bloom was noticed during December•No indication of pollution was noticed in terms of the parameters measured