Study of Macroinvertebrates Assemblage as an Indication of a Tropical Freshwater Lagoon Water Quality: Ono Lagoon (Côte d’Ivoire, West Africa)

Macroinvertebrates are diverse array of animals without backbones operationally defined as those that are retained by a sieve or mesh with pore size of 0.2 to 0.5 mm, as used most frequently in stream sampling devices. Lagoon macroinvertebrates include various groups of worms, molluscs, crustaceans, mites, and above all insects (Winterbourn, 2008). Most invertebrates are important components of lagoon ecosystems. They graze periphyton, assist in the breakdown of organic matter and cycling of nutrients and, in turn, may become food for predators (Hynes and Naba, 2012). Macroinvertebrates are the organisms most commonly used for biological monitoring of freshwater ecosystems worldwide. This is because they are found inmost habitats, have generally limited mobility, are quite easy to collect by way of well established sampling techniques, and there is a diversity of forms that ensures a wide range of sensitivities to changes in both water quality (of virtually any nature) and habitats (Hellawell, 1986; Abel, 1999). Studies of aquatic ecosystems macroinvertebrates as biological monitoring techniques have been widely reported and described in the literature (Hart et al.,1999; Touzin, 2008; Odountan, and Abou, 2015). Macroinvertebrates assemblages have been widely used as biondicators of the overall health of different aquatic ecosystems within several biotic indices (Raburu et al., 2009a, 2009b). Freshwater macroinvertebrates species vary insensitivity to organic pollution and, thus, their relative abundances have been used to make inferences about pollution loads. In Ono lagoon, increased deforestation and unsustainable agriculture coupled with agro-industrial activities pose threats to the wellbeing of aquatic ecosystems. Major industrial activities include agricultural practices of the Alsacienne Society of Côte d‟Ivoire (SALCI) and the Study of Banana Crop (SCB). The proximity of leaching waters of neighbouring agricultural lands is a permanent source of pollution. Given that community livelihoods in Ono lagoon basin revolve around agricultural crop production and fisheries, it is imperative that the wetland ecosystem is closely monitored and conserved to ensure sustainability. Numerous studies have highlighted the importance of using benthic macroinvertebrates for monitoring purposes to support the results obtained regarding physical and chemical variables (Masese et al. 2009; Raburu et al. 2009a, 2009b; Minaya et al. 2013). These organisms were good biological indicators of water quality, due to the fact that they are both abundant and ubiquitous in nature, thereby offering a wide spectrum of observable responses to environmental changes (Turkmen and Kazanci, 2010). Till to date, no study has been undertaken to document the occurrence and distribution of macroinvertebrates assemblage in small lagoon and their response to varying levels of disturbance. The objective of this study is to present the status of water quality and ecosystem health of Ono lagoon using the most community structure indices such as Biological Monitoring Working Party (BMWP) and Pollution Tolerance Index (PTI).