Zooplankton-based assessment of the trophic state of a tropical forest river in Nigeria

Abstract

In this study, we explore the usefulness of zooplankton as a tool for assessing the trophic status of a Nigerian forest river. The river was sampled monthly and investigated for water physico-chemistry and zooplankton community structure using basic statistical measurement of diversity indices to characterize the zooplankton fauna. The trophic sta­tus of the river evaluated from its physico-chemical parameters indicates that the river is oligotrophic. The zooplankton composition was typical of a tropical freshwater river, with a total of 40 species, made up of 16 rotifers, 12 cladocerans, and 12 copepods and their developing stages in the following order of dominance: Rotifera > Cladocera > Cyclopoida > Calanoida. There were strong correlations between the lake's trophic status and its zooplankton communities. The zoo­plankton community was dominated by numerous species of rotifers and crustaceans, which are typical of oligotrophic to mesotrophic systems, such species including Conochilus dossuarius and Synchaeta longipes. However, the most dominant zooplankton species in West African freshwater ecosystems, viz., Keratella tropica, Keratella quadrata, Brachionus angularis, Trichocerca pusilla, Filinia longiseta, Pompholyx sulcata, and Proales sp., and others that are indicator species of high trophic levels, were not recorded in the river. The river is very clear and can be used for all manner of recreational activities

Water quality assessment of Osse River, Gele-gele: a tributary of Benin River, southern Nigeria

“…Dissolved oxygen, which is a measure of the amount of oxygen that is freely available in water, is essential for sustaining aquatic life in any ecosystem. The average value (4.27mg/l) obtained in this study is similar to that obtained in other tropical rivers (Imoobe and Adeyinka, 2010;Anyamwu;2012) from Ogba river. This value is slightly less than the permissible limit (5mg/l) necessary to sustain aquatic life, an indication that the water quality was starting to deteriorate.…”

Assessment of some heavy metals and total hydrocarbons in Clarias gariepinus fish of Osse River, Edo State, Nigeria

“…The river flows in south westerly direction through Nikorowa, Ekewan, Gelegele, and Izedema communities. It is a fresh oligotrophic (Imoobe and Adeyinka, 2009) lotic freshwater, with a thick vegetation canopy along most part of its bank. It is located in the Ovia North-East local of area of Edo State; in the tropical rainforest belt of southern Nigeria.…”

Behavioural and Some Physiological Assessment of Glyphosate and Paraquat Toxicity to Juveniles of African Catfish, Clarias gariepinus

“…Run-off of herbicides from agricultural lands into natural water bodies have become a worldwide phenomenon. Due to the different pollutants entering the aquatic ecosystems, the organisms there are subjected to environmental stresses which may be deleterious to them, to a population or to a community and eventually causing an alteration in the structure of natural ecosystems (Imoobe and Adeyinka, 2010). The quality of fish food is inexorably linked to the health of fish which itself is dependent on the level of pollutants in the aquatic environment (Verma et al, 1981).…”