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International Journal of Environmental Sciences
Year : 2012, Volume : 3, Issue : 1
First page : ( 371) Last page : ( 385)
Online ISSN : 0976-4402.
Article DOI : 10.6088/ijes.2012030131035

Seasonal influence of water quality of Batticaloa Lagoon, Sri lanka on fish and plankton abundance

Harris J.M.*, Vinobaba P

Department of Zoology, Eastern University, Sri Lanka, Vantharumoolai, Chenkaladi - 30350

*Email: harriseusl@gmail.com

Online published on 26 November, 2013.

Abstract

Assemblage of lagoon organisms vary in time and space, largely because widely varying of environmental characteristics prevails on lagoon. This study is aimed to assess the impact of water quality of Batticaloa lagoon in relation to changes in fish and plankton abundance. In situ measurements of chemical and physical parameters of the lagoons were recorded fortnightly by calibrated portable water quality Hanna instruments over wet and dry seasons for 15 months from July 2008 to December 2010. Standard methods were used to collect the fish and plankton samples from Batticaloa lagoon. Dissolved oxygen (4.15 ± 0.40 to 15.66 ± 0.24 mg/L), salinity (8.10 ± 1.35 to 30.16 ± 0.23 ppt), nitrate (2.07 ± 0.22 to 3.71 ± 0.72 mg/L) and pH (8.01 ± 0.02 to 8.16 ± 0.05) showed significant seasonal variation. Analysis elucidated that the existing conditions were found to have strong impact on fish community. Comparatively, a higher number of species was recorded in the dry season than in the wet season. However, there was little variation in species composition with respect to seasons. Out of 28 families of 42 species sampled, 4 species were restricted to wet season, while 5 species occurred in both seasons such as families Mugilidae, Clupeidae and Cichilidae. Seasonal differentiation of all species sampled revealed higher values for the dry season than in the wet season. The 2 holoplankton groups of species increased in abundance during the wet season, while about 4 species lacking seasonality. The majority of zooplankton species of Batticaloa lagoon are typical of strongly brackish water although the northern part of the lagoon shows a mixture of marine species and brackish water. Most of the dominant species of phytoplankton were not considered as harmful and dangerous for human health. However, certain species of Anabaena, Microcystis, Oscillatoriya are known to produce certain neurotoxin, hepatotoxin and skin damages. In addition Amphidinium sp also observed in the lagoon produce biologically active haemolytic compounds and may be implicated in ciguatera (phytotoxin). These have to be viewed as a threat to lagoon food safety. This information enables natural resource managers to determine where our lagoons are under stress and where to invest in environmental management activities. It also helps State Government agencies address for monitoring, evaluation and reporting.

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Keywords

Fish community, lagoon, seasonality, water quality, zooplankton.

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