MAJOR FACTORS THAT STRUCTURE THE BENTHIC FAUNA OF A SHALLOW, TROPICAL LAKE, LAKE KURIFTU, ETHIOPIA
Abstract
The aim of this study was to determine the community structure of the benthos in Lake Kuriftu in relation to some environmental
variables. Benthic samples were collected with an Ekman grab (0.0225 m 2 ) from three sites (littoral, sub-littoral and profundal zones) on a monthly basis from September 2009 to February 2010. Dissolved oxygen and temperature were measured with a probe at different depths of each site. Sediment texture was determined by the Bouyoucos hydrometer and organic matter content by loss on ignition method. Chironomids, EPT (Ephemeroptera, Plecoptera, Trichoptera), oligochaetes and coleopterans were abundant in littoral and sub-littoral zones, with EPT much higher in the vegetated littoral area. The mean density of benthic macro-invertebrates in littoral, sub-littoral and profundal zones was 20,443, 18,251, and 4,388 ind/m 2 , and that of Chironomids was 12,545, 14,003 and 3,215 ind/m 2 , respectively. The profundal zone had the lowest diversity with abundant oligochaetes but no EPT samples, despite the high oxygen content of the profundal zone (6.33 mg/l). Chironomids and oligochaetes were present in all zones which had negligible difference in dissolved oxygen and organic matter content. The littoral zone had highest diversity (H’=1.26) and richness (d=2.72). Our results indicate that abundance of benthic macro-invertebrates of Lake Kuriftu was best correlated with the presence of vegetation in the littoral zone and sediment texture (high clay) in the littoral and profundal zones. We conclude that benthic macro-invertebrate community structure in Lake Kuriftu is mainly influenced by spatial variation in vegetation, sediment texture and temperature, but not dissolved oxygen and organic matter content.
Downloads
References
Baye Sitotaw (2006). Assessment of benthic macro-invertebrate structure in relation to environmental degradation in some Ethiopian rivers. MSc Thesis. Addis Ababa University.
Beneberu, G., S. Mengistou, H. Eggermont and D. Vershuren (2014). Chironomid distribution along a pollution gradient in Ethiopian rivers, and their potential for biological water quality monitoring. Afr. J. Aquat. Sci. 39(1): 45-56.
Betael Assefa (2010). Study of benthic macro-invertebrates in Lake Hayq. MSc Thesis.Addis Ababa University, 56 pp.
Bogut, I., Vidakovic, J., Palijan, G. and Cerba, D. (2007). Benthic macro-invertebrates associated with four species of macrophytes. Biologia 62(5):600-606.
Bouchard, W.R. (2004). Guide to Aquatic Invertebrates of the Upper Midwest. Identification manual for students, University of Minnesota, 207 pp.
Bouyoucos, G.J. (1936). Directions for making mechanical analysis of soils by the hydrometer method. Soil Sci. 42 pp.
Boyd, C.E. (1970). Production, mineral accumulation and pigment concentration in Typha. Ecology 51:285-290.
Brook Lemma, Benndorf, J. and Koschel, R. (2001). Fish predation pressure on and interactions between Cladocerans: Observations using enclosures in three temperate lakes (Germany) and one tropical lake (Ethiopia). Limnologica 31: 209-220.
More inside the PDF
