Abstract
Estuaries are influenced by the mixture of river water with seawater; creating unique ecosystems with several physical and chemical processes affecting the water quality. Spatial and temporal assessment of the composition, abundance, and distribution of zooplankton fauna of Uta Ewa Estuarine water system was carried out between May 2019 and February 2020 to assess the effects of anthropogenic activities on the zooplankton assemblage. Water and Zooplankton samples were collected from three (3) stations using standard procedures. Some parameters like water temperature, dissolved oxygen, hydrogen-ion, electrical conductivity, and turbidity were determined in-situ. The ranges of the physico-chemical parameters were: water temperature (24.9-25.3oC), EC (62.3-70.9mS/m), pH (6.5-6.7), turbidity (12.0-28.0NTU), DO (3.8-4.7mg/L), BOD (2.3-3.2mg/L), phosphate (3.2-5.2mg/L), and nitrate (3.0-6.3mg/L). ANOVA showed a significant difference (p<0.05) in the spatial and temporal means values of some parameters. A total of 1,067 individuals from 30 zooplankton taxa and 4 taxonomic groups were recorded. Rotifers (33.4%) were the dominant group, followed by protozoa (32.9%), copepods (20.9%) and cladocerans (13.8%). Station 1 had the highest abundance (388 individuals), station 2 (303 individuals) and station 3(375 individuals). The higher number of individuals (193) was recorded in August 2019. The biodiversity indices pointed to slightly polluted to stable environment. This study showed that the water quality and zooplankton community was influenced by anthropogenic activities both spatially and temporally but season also played a major role in the temporal variation. In conclusion, the water quality was deteriorating due to anthropogenic activities, which in turn affected the structure of zooplankton community. Keywords: Abundance, Assessment, Zooplankton, Physicochemical, Estuary
Highlights
Complex and dynamic aquatic ecosystems exist within the estuary and coastal areas (Morris et al, 1995)
Related studies have shown that zooplankton abundance in the water body is associated with the seasonal fluctuations in some aspect of hydrochemistry concentration in the water body (Essien-Ibok & Ekpo, 2015; Jonah & George, 2019)
Uta Ewa Estuary is characterized by heterogeneous forms of anthropogenic activities, and it is the major source of water for irrigation and other domestic purposes communities within its watershed
Summary
Complex and dynamic aquatic ecosystems exist within the estuary and coastal areas (Morris et al, 1995). Zooplankton are microscopic animals that are an indispensable constituent of aquatic food webs; an important link in the energy conversion from producers to consumers (Sousa et al, 2008; Sharma et al, 2010) They could be non-motile or very poor swimmers; drifting in the water column of water bodies and depends on water to get to any great distance (Ferdous & Muktadir, 2009). Related studies have shown that zooplankton abundance in the water body is associated with the seasonal fluctuations in some aspect of hydrochemistry concentration in the water body (Essien-Ibok & Ekpo, 2015; Jonah & George, 2019) Human activities such as industrial, indiscriminate disposal of wastes and agriculture are leading contributors to pollution in the aquatic ecosystem (Anyanwu et al, 2013; Jonah et al, 2019; Anyanwu & Umeham 2020a; Jonah et al, 2020); these activities alter the favorable water quality for zooplankton growth and development. The objective of this study was to assess the effect of anthropogenic activities and season on the zooplankton assemblage of the estuary
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