Assessing The Ecological Character Of Wetlands And Their Impact On The Distribution And Abundance Of Water birds In Some Coastal Wetlands In Ghana

Abstract

This study sought to assess the ecological character of the Sakumo II, Laloi and Kpeshie coastal wetlands in Ghana as these wetlands face massive degradation largely driven by urbanization and the rapidly growing human population in these areas. Specifically, the study investigated the quality of water and sediments, the changes in the physical characteristics (land use/land cover), the distribution of benthic macroinvertebrates, the growth and condition factor of the predominant fish species in lagoons in Ghana (Sarotherodon melanotheron), and how they influence the abundance and distribution of waterbirds on these wetlands. Data for this study were obtained from direct field observation and laboratory analysis. Counting of waterbirds was done by using a Swarovski 20 x 60 telescope while sampling and laboratory analysis of water and sediment were done by using approved standard methods (APHA, 2005). The sampling and sorting of benthic macroinvertebrates into their various taxa were also done by appropriate keys and guides. The standard length and weight of the blackchin tilapia (Sarotherodon melanotheron) were measured using the rule and Mettler Toledo Weighing balance while Landsat thematic images were freely downloaded from the United States Geological Survey (USGS) for the years 1986, 2002, and 2017. A total of 24,247 individual waterbirds belonging to 13 families were counted monthly on all three wetlands over a period of one year. Fifty (50) different waterbird species were recorded with the most abundant species belonging to the family Scolopacidae (88.71%) which were mostly waders. In terms of abundance of waterbirds on each site, 12,143 individual waterbirds representing 50.1% of total count was recorded on the Laloi wetland with the Common Ring Plover (Charidrius hiatucula) being the dominant species. The Sakumo II had a record of 10,116 waterbirds representing 41.7% with the Collared Pranticole (Glareola prantincola) as the most dominant. The Kpeshie wetland recorded 1,988 representing 8.2% of the total count with the Common Sandpiper (Actitis hypoleucos) as the most abundant waterbird. In terms of land use land cover changes (LULC) on the wetlands, there was a decrease change of 57.3% of the vegetative cover and 0.6% of waterbodies between 1986 and 2017 with a corresponding increase of built-up areas by 54.4% on the Sakumo II wetland. Vegetative cover and waterbodies also decreased by 58.3% and 6.6% on the Laloi wetland with a resultant increase of 53% in built–up areas over the same period. Furthermore, the vegetative cover and waterbodies III I decreased by 33.7% and 15.2% on the Kpeshie wetland while built-up increased significantly by 50.8%.There were significant positive correlation between conductivity and nitrite (r=0.698, r=0.760, p<0.01 respectively) likewise an inverse relationship between water depth, phosphate and nitrate (r=-0.998, r=-0.920, r=-0.981; p<0.01 respectively) and built-up on the Sakumo II wetland. Land use land cover variables together accounted for 26.8% of the changes in abundance of waterbirds during the study. Built-up and vegetation had a significantly negative relationship with waterbirds abundance [β=-0.651; p<0.05] [β=-1.185; p<0.05] while waterbodies and barelands had a significantly positively relationship with waterbird abundance [β=0.487; p<0.05] [β=1.430; p<0.05]. The mean pH(7.65 ±0.65, 8.05 ±0.65, 7.92±1.30) and temperature (29.23 ±1.35oC, 28.76 ± 0.74oC and 29.71 ±2.11oC) of water samples collected from the Sakumo II, Laloi and Kpeshie wetlands respectively were typical of shallow coastal waters in Ghana with ambient pH and temperatures within a narrow range of 6 - 9 and 25-35 0C. The BOD, turbidity, phosphate and nitrate levels in water samples on both the Sakumo II and Kpeshie wetland were above the WHO permissible limits. Based on the pollution load index (PLI) estimated for all the wetlands using the bottom sediment, there was no overall pollution of heavy metals in sediment although some sites showed extreme enrichment (PLI<1). Heavy metals in PC1, PC2 and PC3 jointly and significantly contributed 25%, 57% and 30% respectively to macroinvertebrates abundance at the Sakumo II, Laloi and Kpeshie wetlands [R2=0.25 p<0.05; R2=0.57, p<0.05; R2=0.30, p<0.05]. A total of 4,474 macroinvertebrates individuals belonging to three major phyla (Annelida, Mollusca and Crustacean) were recorded during the study. Hydrobia spp, Cerithedia spp and the Nereis spp were the most abundant on the Sakumo II, Laloi and Kpeshie wetlands respectively. Macroinvertebrates abundance contributed 12%, 22% and 4% to waterbirds abundance at Sakumo II, Laloi and Kpeshie wetlands respectively [R2=0.12, p>0.05; R2=0.22, p<0.05; R2=0.04, p>0.05]. Sarotherodon melanotheron fishes in the Sakumo II lagoon exhibited isometric growth (‗b‘ is nearer to 3) while a negative allometric growth pattern was observed in fishes from the Laloi and Kpeshie lagoons. Mean condition factors estimated for Sarotherodon melanotheron on all wetlands were greater than one (1) indicating a good environment for fish survival and abundance. Fish condition factor also significantly contributed to 25%, 34% and 35% of waterbirds abundance on the Sakumo II, Laloi and Kpeshie wetlands respectively [R2=0.25 p<0.05; R2=0.34, p<0.05; R2=0.39, p<0.05]. IV I There have been major changes in the quality of water and sediment on all three wetlands, likewise, significant changes in the vegetative cover, waterbodies and built-up areas between 1986 and 2017 due to human interferences on the wetlands. The unprotected Laloi wetland, however, supported the highest number of waterbirds compared to the protected Sakumo II wetland during the study. Major stakeholders like the EPA, the Water Resources Commission, the Forestry Commission, the Ghana Wildlife Division as well as the District and Municipal Assemblies should enforce all existing laws that will help conserve and protect these wetlands from further deterioration. Education and awareness creation on the level of usage, importance and benefits derived from these urban coastal wetlands should be intensified within the catchment areas as human population continues to increase inorder to achieve Goal 6, 14 and 15 of the Sustainable Development Goals (SDG) in and around these urban wetlands