Lucknow 226 002 UP India. Abstract: Physicochemical variables and zooplankton of Ologe Lagoon were studied in three stations (station. 1, the point at which ...
J. Ecophysiol. Occup. Hlth. 9(2009) 67-75 ® 2009 The Academy of Environmental Biology, India
Variations in Zooplankton in Response to Physicochemical Changes in a Tropical Coastal Lagoon O. I. Okogwu and C.D. Nwani1 Applied Biology Department, Ebonyi State University, PMB 53, Abakaliki, Ebonyi State, Nigeria. 1 National Bureau of Fish Genetic Resources, Indian Council of Agricultural Research, Lucknow 226 002 UP India. Abstract: Physicochemical variables and zooplankton of Ologe Lagoon were studied in three stations (station 1, the point at which river Owo enters the Lagoon, Station 2, fish landing site and station 3, the middle of the Lagoon) during the dry and wet seasons of 2000. Multidimensional scaling (MDS), correlation and analysis of variance (ANOVA) were used to test for temporal and spatial variation in environmental and zooplankton data. The first two MDS axis explained 51.3% of the variation in environmental data. Twenty one taxa (21) of zooplankton were identified as Protozoan (5), Rotifera (12), Cladoceran (3) and Copepoda (1). Rotifers dominated the zooplankton and the dominant species were Brachionus falcatus, B. patulus and Keratella tropica. The crustaceans were only seen during the period of low salinity when they became dominant in Station 2. Zooplankton density increased with increase in diversity in Station 1 but declined with increased diversity in Stations 2 and 3. There was also an increase in zooplankton abundance and diversity with increase in rainfall. This was attributed to dilution effect of rain on the lagoon waters, which allowed the establishment and proliferation of salinity intolerant species. The absence of crustaceans from Station 1 was mainly attributed to low dissolved oxygen (
