Aquatic Macrophytes and Their Impact on Water Quality of Lekan Aare Lake, South West Nigeria

Abstract

Survey of Aquatic Plants of Lekan Aare, South West Nigeria was carried out between May and August 2005. The aquatic plants located along the edge of the lake and the ones in the lake water (reservoir) were all collected, identified and classified into 13 families. Macrophytes abundance, distribution, species diversity, species zonation and similarity indices were studied within the chosen sampling area of 3,600 m2 using transect lines. Their percentage distribution along the entire stretch of the lake was calculated using Sorensen‟s (Simpson‟s similarity index). The Families Cyperaceae and Poaceae topped the list by having 4 species each while the others had 1 species each. The species diversity ranged between 1.04 – 23.68% with Azolla africana having the highest species diversity of 23.68% while Ceratophyllum demersum had the lowest value (1.04%). Species richness (abundance) revealed that Azolla africana had the highest value (0.03) while Fimbristylis ferruginea had the lowest species distribution (evenness) of 0.38% with Ludwigg decurrens and Luffa aegyptiaca having the highest value of 1.00%. Zones II and III had the highest similarity index (73.68%) of all the zones while zones I and III had the least (31.58%). 13 of the aquatic plants species were emergent, 2 species were floating while 1 species was found submerged in water. The water quality was observed to be clear with low concentration of suspended sediments and maintained good dissolved oxygen level of 5.53mg/l and pH of 7.62 implying low level of production.

Key words: Aquatic plants, Lekan Aare Lake, Macrophytes, South West Nigeria.