Plankton Dynamics as Pollution Indicator in the Coastal Waters of Ondo State, Nigeria

Abstract

The dynamics of planktons in the coastal waters of Ondo State, Nigeria were investigated from April, 2014 to March, 2016. Samples were collected monthly using plankton net of 55 μm-mesh size, preserved in 4% formalin, examined with Olympus microscope and identified using standard guides. Zooplankton was more abundant in the environment in this study with NOI of 55.54% and 53.25% in the wet and dry seasons respectively. A total of twenty-three species of phytoplanktons belonging to two taxonomic groups were recorded. Diatom (65.22%) represented by five phyla consisting of Ochrophyta (7species), Heterokontophyta (6species) and Bacillariophyta (2species) while Dinoflagellates (34.78%) were represented by phylum Dinoflagellata (4species) and Myzozoa (4species). The zooplankton assemblage was composed of twenty-seven species including phylum Arthropoda (10), Rotifera (6), Chordata (3), Chaetognatha (2), Echinodermata (2), Ciliophora (1), Cnidarian (1), Granolereticulosa (1), and Mollusca (1). In wet-season, Fish-eggs (4.69%) (most abundant) Brachionus quadridentatus (3.79%); Coscinodiscus sp (3.67%); Biddulphia mobiliensis (3.31%) and Odonata nymph (3.01%) with Foraminifera (0.60%, the least) while the composition of the dry-season had a descending trend of Asterionellopsis sp (3.25%)>Cerataulina sp and Pseudo-nitzschia sp (3.02%)>Chaetognatha adult (2.86%)>Brachionus falcatus; Ceratium hirundinella sp and Coscinodiscus sp (2.70%)>Gyrodinium spp (2.62%) to Protoceratium reticulatum (0.48%). The Number of Individuals ranged from 26.25±6.86 (Dry-season) to 38.85±16.33 (Wet-Season) while Number of the most abundant species (Nmax) and average number of species (S) (which exhibited seasonal variation at P<0.05) ranged from 2.92±0.87 (Dry-Season) to 3.92±1.18 (Wet-Season) and from 18.10±3.14 (Dry-season) to 20.38±5.72 (Wet-Season) respectively. The Margalef’s Diversity Index and Shannon-Wiener Index which showed no seasonal variation ranged from 5.25±0.70 to 5.35±1.28 and 2.80±0.18 to 2.86±0.29 respectively, while Simpsons-Reciprocal Index ranged from 32.25±12.74 (Wet-Season) to 40.10±15.84 (Dry-season) and exhibited seasonal variation at P<0.05. The abundance and diversity of planktons in this study is an indicator of eutrophic ecosystem that is possibly unstressed.

Keywords: Abundance, Brackish-water; Planktons; Eutrophic; Diversity Index, Composition, Nigeria


Article Review Status: Published

Pages: 22-31 (Download PDF)

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