Temporal and Spatial Variations in Abundance and Diversity of Zooplankton Fauna of Opa Reservoir, Obafemi Awolowo University, Ile-Ife, Southwest Nigeria

Abstract

The present study investigated the ecological status of Opa reservoir, Obafemi Awolowo University, Ile Ife, Nigeria, based on the spatial and temporal variations in abundance and distribution of zooplankton. 72 samples were collected monthly with a quantitative net zooplankton from both the surface and bottom levels in three stations established at the dam site (Lacustrine), mid-lake (Transition) and inflow (Riverine) over a period of an annual cycle. A total of fifty-four (54) species were recorded from the reservoir comprising Rotifera (57.41%) > Arthropoda (33.33%) > Protozoa (5.56%) > Ciliophora (1.85%) = Cnidaria (1.85%), in the order of abundance. The least number of species (47) was recorded at the Transition station, while the highest number of species (49) occurred at the Lacustrine zone. Of all the zooplankton recorded, four species had significant spatial variation, while nine displayed seasonal variations during the study period (p ≤ 0.05). The highest species richness was observed in Transition surface station (4.18), followed by Lacustrine surface station (3.80) and Riverine surface station (3.23). Shannon's index showed that zooplankton species were more diverse during the rainy season than dry season. The highest Trophic State Index (TSI CR ) with respect to Rotifer abundance occurred in Transition surface, followed by Riverine surface and the least occurred in Transition bottom portion. The mean TSI CR value obtained was 65.20, indicative of hyper-eutrophic, while the mean TSI CL value with respect to cyclopoida-calanoida obtained was 58.07 also revealing eutrophic status of the study area. Opa reservoir comprises mainly Rotifers and its TSI CR showed the lake as eutrophic, tending towards becoming hyper-eutrophic, which could speed up the aging of the lake.

Impact of Hindiya Dam on Rotifera Community of Euphrates River on the Northern of Babil Governorate, Iraq

“…The lowest values were at sites 4 in January, whereas the highest value was at site 5 in June (Figure -3). As for spatial variation, site 5 had high density may due to it had favorable conditions for rotifers growth such as higher value percentage oxygen saturated [28], and the presence of macrophytes [29].…”

“…While, Shannon's index values were reduced with a less water current velocity ˂0.1 m s/L, when discussed man-made ditch in the Drawa catchment (Poland) which are similar with influence of artificial dams. As well as, Czerniawski et al [28] when studied Barycz River and its tributaries which are outlets of carp ponds (in Poland).…”

The Effect of Tharthar-Tigris Canal on the Environmental Properties of the Tigris River Northern Baghdad, Iraq

“…River channel confluences are sites of significant hydraulic and morphological change within fluvial networks. The local and downstream effects of confluences can have profound effects on the physical water parameters and aquatic animal structures 4,5 .The portion of the river system affected by merging of flows at a junction is defined as Confluence Hydrodynamic Zone (CHZ). Also, confluences play a crucial role in the health of lotic water system and regulate the dynamic of sediment downstream the joining point 6 .…”