AUTHOR=Hsieh Hsueh-Han , Chuang Ming-Hsiu , Shih Yung-Yen , Weerakkody W. Sanjaya , Huang Wei-Jen , Hung Chin-Chang , Muller François L. L. , Ranatunga R. R. M. K. P. , Wijethunga D. S. 

TITLE=Eutrophication and Hypoxia in Tropical Negombo Lagoon, Sri Lanka

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 8 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2021.678832

DOI=10.3389/fmars.2021.678832

ISSN=2296-7745

ABSTRACT=Hypoxic events becoming frequent in some estuaries and coastal waters due to over-enrichment of anthropogenic nutrients, organic matter and/or due to restricted water circulation. The coastal lagoon estuaries of Sri Lanka are increasingly susceptible to these hypoxic conditions because they are located on the edge of densely populated areas, have relatively sluggish circulation and receive increasing anthropogenic inputs of nitrogen and phosphorus. In this study, we examined the spatiotemporal variability of eutrophication and hypoxia in the Negombo Lagoon, one of the most productive and sensitive coastal ecosystems in Sri Lanka. Based on seasonal measurements of dissolved oxygen, nutrients, chlorophyll-a, particulate and dissolved organic carbon (POC and DOC), we concluded that eutrophication and hypoxia occurred in both the dry and wet seasons. The main contributing factors were high seawater temperature and poor water circulation in the dry season and high nutrient loading combined with elevated POC and DOC inputs in the wet season.