No abstract

Asu River is one of the major tributaries of Cross River, a tropical reforest river in southeast Nigeria. The climate of the region is divided into the wet and dry seasons. Human activities such as fishing, bathing and washing go on in the river especially during the dry season. Farming also takes place at the fringes of the river. Some important physicochemical parameters of the river were investigated at two designated sites comprising the downstream and the upstream for nine (9) months, from October, 2013 to June, 2014. Temperature, carbon (iv) oxide, conductivity, total dissolved solids, nitrate and phosphate recorded maximum values during the dry season while dissolved oxygen and pH recorded maximum values in the wet season. The physicochemical variables evaluated showed that the river is not in a critical condition as most of the variables recorded are within the WHO permissible limit. However, the paper therefore recommends the need for public enlightenment on environmental management and control of household and industrial wastes in order to sustain the usefulness of Asu River.

Small rivers provide important ecosystem services and harbour a rich biodiversity. Nevertheless, their ecology is still poorly understood in many parts of the world due to the paucity of studies. To this end, the water quality and zooplankton structure of several first order rivers in Ebonyi State, Nigeria were studied for the first time to assess the factors that influence the species diversity, abundance and biomass. Samples for water quality parameters and zooplankton analyses were collected for eighteen months using a standard procedure. The results showed a significant (p < 0.05) seasonal variation in mean air and water temperatures, conductivity, total dissolved solids, flow rate, and dissolved oxygen. Rotifera dominated zooplankton abundance and biomass and were the most diverse group. Cladocera contributed most to zooplankton species richness at the Ebyia and Idumayo rivers in the dry and rainy season, respectively. The dominance of Brachionus spp., Filinia longiseta, Cyclops spp. and nauplii indicated organic pollution at some of the rivers in the dry season. The Canonical Correspondence Analysis showed that temperature, water flow rate, transparency, conductivity, TDS, dissolved oxygen, and available phosphate were the major factors that affected zooplankton abundance, diversity, species richness and biomass in the rivers during the study.