Application of Macrobenthic Faunal Indices in Assesssing the Ecological Quality Status of Laloi Lagoon of Ghana

Abstract

The aim of this study was to assess the macrobenthic fauna structure and use its indices as a tool for characterizing the ecological state of the Laloi lagoon. Thus, a field assessment of the benthos in the Laloi lagoon was carried in January 2012. Four replicate samples were taken at each station contained in three zones and analysed for their structure and composition. Twenty-one (21) species of macrobenthos belonging to 19 genera were identified. The highest number of species belonged to Polychaetes (15 species) followed by Bivalves (6 species) and 1 species of Gastropod. The grain size of sediments and total organic matter as essential factors in distribution and population diversity of macrobenthos communities were also analysed. The results showed that all of the stations were characterized by medium sand to very fine sand. Shannon-Wiener index (H'), species richness (S) and Pielou’s evenness were calculated and they revealed a high species diversity with variability in abundance within stations. The ecological indices, such as (AMBI, M-AMBI, BENTIX and H’) were also applied to the available benthic species data to determine the ecological status of the lagoon. AMBI, M-AMBI, H' and BENTIX gave different results regarding the boundaries for High, Good and Moderate and it was worse when applying H' and BENTIX. However, the index AMBI provided a more suitable evaluation of EcoQS corresponding to ‘slightly polluted’ lagoons in compliance with univariate community indices.

Keywords: Macrobenthic Faunal Indices, Laloi Lagoon, Ecology