Littoral Vegetation and Physico- Chemical Characteristics of the Owabi Lake in Ghana

Abstract

The littoral zone of water bodies serves as a habitat for plants and food source for fishes but could be detrimental to the longevity of the lake if the growth and spread of plants are not controlled. The littoral zones of the Owabi Lake is influenced by four river inlets that bring into the lake a lot of sediments and other pollutants. Though these may be detrimental to the water body, they also serve as nutrient source for the littoral vegetation. No work has been done previously on the characteristics of the littoral vegetation of the Owabi Lake. The study thus assessed the general floristic characteristics and the water quality of the Owabi Lake. The littoral perimeter of the lake was divided into zones of 78 plots with 5 m X 5 m quadrats at 50 m intervals. The plant species within each plot was assessed and enumerated. Additionally, the physico-chemical characteristics of the littoral zone were determined using standard protocols. The study yielded a total of 30 plant species which belonged to 25 families. Acrocera zizanioides recorded the highest density of 91.21% but relative frequency of 16.08%. An algae, Lemna minor registered the highest relative frequency of 16.35% but a relative cover of 0.013%. Acrocera zizanioides had the highest IVI of 107.30 with the herbs Chromlaena odorata and Lugwigia alata indicating an IVI of 0.27. Species from the Asteraceae family had the lowest relative density (<1%). The lower portion of the lake recorded higher plant cover with H and 1-D alpha diversity analysis indicating lower diversity within the plants species (H<2.0), with the evenness being significantly different (p=0.03) between the lower and upper portion of the lake. The physico-chemical characteristics of the lake indicated higher concentrations at the lower portion, and that influenced the inward growth of plants into the lake. The values obtained were within the WHO limits with only the light intensity being very low at the upper portion due to shades from tree covers. The higher concentrations of nutrients with adequate light intensity at the lower portion of the lake could account for the relative higher density and IVI of plants at that part of the lake. The uncontrolled inward growth of plants at the lower portion of the littoral zone of the Owabi lake could narrow its size with time and poses danger to the sustainability of the water body.