Study on zooplankton distributions in Mahin Lagoon within transgressive mud coast, Ondo, Southwest Nigeria

Abstract

Distributions of zooplankton were studied in Mahin Lagoon within the transgressive mud coastal zone, Southwest Nigeria. Zooplankton samples were collected at fifteen stations along the stretch of the lagoon and analysed using standard methods for four months (October 2013, 2014, March 2014 and 2015). In each of the rainy and dry seasons, zooplankton recorded belonged to phyla Foraminifera, Arthropoda, Rotifera, Ciliophora and Protozoa. During rainy season, when salinity levels were relatively low, rotifers constituted the dominant zooplankton fauna whereas tinttinids (ciliophorans) and copepods (crustaceans/arthropods) were the major taxa recorded during dry season when salinity was high in some stations. March 2014 and 2015 recorded higher zooplankton abundance and species diversity than October 2013 and 2014 across the fifteen stations. The distributions of species across different stations were however relatively uniform during October 2013 and 2014. Ciliophorans (such as Tintinnopsis, Codonellopsis spp) were distributed mostly within the stations close to the Atlantic Ocean with higher salinity while freshwater stations further upstream were prevailed mostly by rotifers (such as Ascomorpha, Brachionus, Keratella, Filinia spp.). Copepods (such as Acartia, Paracalanus, Parapontela spp) and Cladocerans (such as Bosmina, Moina and Penilia spp) however were distributed across the entire study area. The imperativeness of sustainably managing the water body and resources therein is discussed.

Keywords: Zooplankton abundance, species diversity, coastal waters, salinity, sustainable management