Water quality and plankton biota of Osinmo reservoir, Osun State, south-west Nigeria

Abstract

The study aimed at determining spatial and temporal changes in physico-chemical water quality and planktonic composition in relation to rainfall patterns was carried out in Osinmo reservoir, an impoundment on the Ataro River, Osun State, Nigeria, over a period of six months (May-October 2011). The effect of rains and reservoir zonation on the investigated parameters varied widely. A wide range of DO, BOD 5 , organic carbon and transparency values was recorded both temporally and spatially. The rainfall pattern affected four out of the nine investigated chemical parameters (conductivity, alkalinity, carbonate and organic carbon). Water conductivity was found to be highly variable during the three phases of the annual rainy season. The lacustrine zone was characterised by the highest content of organic carbon, considerably differing from that in other zones, and the greatest abundance of plankton followed by that in the transitional zone. The variation in plankton abundance was highly significant (p < 0.05) temporally, but showed no significance (p > 0.05) spatially. The fluctuations recorded, particularly in conductivity and organic carbon concentrations, showed that the influx into the reservoir via rainfall should be monitored in order to prevent reservoir pollution.Buvo tiriamas kritulių poveikis vandens fizinių-cheminių parametrų ir planktono struktūros kaitai. Tyrimai atlikti 2011 m. gegužės-spalio mėnesiais Nigerijoje, Osuno valstijoje esančioje Osinmo vandens saugykloje, atsiradusioje užtvenkus Ataro upę. Deguonies koncentracija, biocheminis deguonies poreikis, organinės anglies kiekis vandenyje ir vandens skaidrumas skyrėsi priklausomai nuo kritulių periodiškumo ir saugyklos vietos. Kritulių periodiškumas turėjo įtakos keturiems iš 9 tirtų cheminių vandens parametrų (laidumui, šarmingumui, karbonatų ir organinės anglies kiekiui). Lietingojo periodo metu labai kito vandens laidumas. Ežerinėje (giliausioje) vandens saugyklos zonoje nustatytas didžiausias organinės anglies kiekis (ženkliai besiskiriantis nuo kitų zonų), joje buvo gausiausia planktono. Planktono gausumo pokyčiai laike buvo patikimi (p < 0,05). Vandens parametrų pokyčiai rodo, kad siekiant išvengti vandens taršos saugykloje, būtina stebėti kritulių sukeltą vandens prietaką.

Assessment of the Ecological Status of OPA Reservoir, ILE IFE, Nigeria Based on a Comparative Study of its Planktonic Community and Water Quality Parameters

“…While obstruction of light depicted by maxima turbidity at the transition led to reduction in growth and minima phytoplankton abundance recorded at the zone. Moreover, the highest phytoplankton abundance recorded from the lacustrine might be as a result of less turbulence and more restricted movement unlike riverine, which is the inflow, characterized by very high turbulence [43].…”

Effects of discharge from carwash on the physico-chemical parameters and zooplanktonic abundance of Odo-Ebo River, Ile-Ife, Nigeria

“…The effect of the effluent was also revealed in the temporal abundance of the zooplankton with 11 out of the 31 species recorded having highly significant seasonal variation, 9 of which were more abundant in the rainy season. Moreover, zooplankton abundance during the rainy season was twice that of the dry season, which has been attributed to nutrient influx with run-off [32]. Adeniyi and Adedeji (2007) [33] also attributed the qualitative richness to the mixing effects of the runoff, which usually frees organisms from river beds and littoral vegetation.…”

Ecological Status of Opa Reservoir, Obafemi Awolowo University, Ile Ife, based on the Abundance and Diversity of its Planktonic Flora

“…The observed irregular variation in phytoplankton distribution from surface to bottom across the three sampling stations could be as a result of high mixing and nutrient re-cycling in the reservoir column during the rainy season (Ugwumba and Ugwumba, 1993;Adedeji et al, 2015). The higher planktonic composition recorded during the rainy season may furthermore be due to an increase in ionic dilution during this period as well as an increase in nutrient inflow and introduction of organic matter (Adedeji et al, 2015).…”

“…The lowest abundance in spite of high species richness recorded in April 2013, a period towards the first peak of the rainy season, could possibly be an effect of the washing away of many individual phytoplankton through flooding and their dislodging from littoral vegetation hence species enrichment (Adeniyi and Adedeji, 2007). The observed irregular variation in phytoplankton distribution from surface to bottom across the three sampling stations could be as a result of high mixing and nutrient re-cycling in the reservoir column during the rainy season (Ugwumba and Ugwumba, 1993;Adedeji et al, 2015). The higher planktonic composition recorded during the rainy season may furthermore be due to an increase in ionic dilution during this period as well as an increase in nutrient inflow and introduction of organic matter (Adedeji et al, 2015).…”

“…The maximum phytoplanktonic abundance, recorded in the lacustrine zone, might be due to stability of certain environmental variables in this zone as a result of reduced water current, restricted movement and higher transparency (Salem, 2011;Adedeji et al, 2015). The lowest abundance in spite of high species richness recorded in April 2013, a period towards the first peak of the rainy season, could possibly be an effect of the washing away of many individual phytoplankton through flooding and their dislodging from littoral vegetation hence species enrichment (Adeniyi and Adedeji, 2007).…”