The Environmentalist, 24, 49–55, 2004  2004 Kluwer Academic Publishers. Manufactured in The Netherlands. The Water Quality of some Tropical Freshwater Bodies in Uyo (Nigeria) Receiving Municipal Efﬂuents, Slaughter-House Washings and Agricultural Land Drainage ANTHONY W. AKPAN ∗ Department of Zoology, University of Uyo, P.M.B. 1017, Uyo, Akwa Ibom State, Nigeria Summary. The water quality of some tropical fresh-water bodies in Uyo (Nigeria) was investigated for two years in relation to point and non-point source city efﬂuents and slaughter-house washings discharged into them. Streams which received city efﬂuents and slaughter-house washings were degraded in quality with acidic water (pH = 5.26 ± 0.83 to 6.20 ± 0.56), low oxygenation (2.46 ± 1.30 to 3.88 ± 0.29 mg l −1 ), high biochemical oxygen demand (4.96 ± 0.66 to 8.20 ± 0.82 mg l −1 ) and chemical oxygen demand (88.60 ± 3.50 to 146.36 ± 9.86 mg l −1 ) than non-efﬂuent receiving streams. High acidity in streams is due mainly to the acidic nature of underground water which replenishes the streams. Nutrient levels were high indicating enrichment from highly fertilized farmlands and slaughter-house washings. The concentrations of most of the hydrochemical variables were signiﬁcantly lower in non-efﬂuent than efﬂuent-receiving streams. Some of the hydrochemical variables (total alkalinity, dissolved oxygen, nitrate, phosphate and conductivity) exhibited pronounced seasonality regimes with signiﬁcant correlations with rainfall indicating its inﬂuence on the chemical hydrology of the water bodies. Land use in the catchment inﬂuenced water quality through inﬂow of nutrients, organic and inorganic contaminants and siltation. Pollution in the impacted streams is attributed mainly to episodic events. Keywords: tropical streams, efﬂuents, land use, water quality Introduction Many of the water bodies in Nigeria receive various forms of pollutants such as industrial efﬂuents, do- mestic sewage, run off from highly fertilized farm- lands, polychlorinated pesticides and other organic contaminants including petroleum hydrocarbon, both crude and reﬁned (Akpan, 1994, 1995; Sangodoyin and Sanyaolu, 1995; King, 1998). Such pollutants de- grade the environment and destroy the habitats with grave consequences to the aquatic biota. The as- sessment of ecological impacts in chemically conta- minated aquatic environments is therefore considered to be necessary for the evaluation of risk to ecosys- tems and the health of human consumers of ﬁsh and shell ﬁsh (Malins, 1989). Some of the pollutants in ∗ Senior Lecturer in Hydrobiology, University of Uyo, Nigeria. aquatic systems enter in intermittent pulses described as episodic (Seager and Maltby, 1989). Such episodic pollution result from farm wastes, domestic sewage and industrial efﬂuents which usually are washed into the stream via runoff. Seager and Maltby (1989) iden- tiﬁed episodic pollution as posing a major problem and being one of the major causes of poor water qual- ity in rivers in the United Kingdom. A lot of the deteri- oration in water quality in rivers in urban and agricul- tural catchments in Nigeria may also be attributed to such pollution. In addition, transient pollution from sewer over ﬂows in urban rivers and the discharge of farm wastes in agricultural catchments have been identiﬁed as major causes of decline in water quality of rivers in England and Wales (Department of the En- vironment, 1986). The objective of the present study was to investi- gate the status of the physico-chemical characteristics