Human Journals Research Article October 2017 Vol.:7, Issue:4 © All rights are reserved by Saki Yao APPIAH et al. Benthic Macroinvertebrates Composition and Spatiotemporal Variation in Relationship with Environmental Parameters in a Coastal Tropical Lagoon (Ebrié Lagoon, Côte D’ivoire) Keywords: Benthic Macroinvertebrates, abundance, community distribution, environmental variables, sectors IV and V of Ebrié lagoon, Côte d’Ivoire Saki Yao APPIAH*, Raphaël N’doua ETILÉ, ABSTRACT Augustin Kouakou KOUAMÉ, Paul Essetchi The Benthic Macroinvertebrates is essential components of an KOUAMÉLAN aquatic ecosystem where it contributes to transferring energy and organic matter from the primary producers to the higher Hydrobiology Laboratory, UFR Biosciences, Félix trophic level taxa. However, changes in some environmental Houphouët-Boigny University, Abidjan-Cocody, 22 BP characteristics strongly influence their diversity and abundance. This work aimed at determining the spatial and 582 Abidjan 22, Côte d’Ivoire, West Africa. seasonal distributions of The Benthic Macroinvertebrates fauna in relation to some physicochemical parameters. The Submission: 19 September 2017 Benthic Macroinvertebrates community of sectors IV and V Accepted: 29 September 2017 of Ebrié lagoon was studied between August 2015 and July Published: 30 October 2017 2016. This study mostly focused on the spatial and temporal distribution, composition and abundance. Ninety-eight taxa belonging to 59 families, 16 orders and 7 classes (Insecta, Gastropoda, Crustaceans, Annelida, Bivalvia, Nematoda and Arachnida) were inventoried in the sectors IV and V of the lagoon during this study. The macroinvertebrates diversity varied according to seasons (20-35 taxa in the dry seasons www.ijsrm.humanjournals.com versus 16-28 taxa in the rainy season). Multivariate analyses (RDA) revealed that The Benthic Macroinvertebrates community composition and abundance variations were mainly controlled by Ebrié lagoon environmental parameters especially water conductivity, pH, temperature, Salinity, transparency, TDS and Depth. www.ijsrm.humanjournals.com 1. INTRODUCTION Coastal lagoons are transition zones serving as ecotones between freshwater, marine and terrestrial biotopes. They contribute to the overall productivity of coastal waters by supporting a variety of habitats, including salt marshes, seagrasses, and mangroves. They also provide essential habitat for many fish and shellfish species. They support a range of natural services that are highly valued by society including fisheries productivity, storm protection, tourism, and others. So, lagoons and estuaries are ecological and social values for riparian population (Antony et al., 2009, Trush et al., 2013). This ecological and social role of lagoons means that they are increasingly undergoing an important anthropogenic impact, which can accelerate natural eutrophication, habitat loss and alteration, chemical contamination, and biotic community's diversity and abundance alteration (Kennish, 2016). In Côte d’Ivoire, coastal lagoons include mainly Grand-Lahou, Ebrié and Aby lagoons. The Ebrié lagoon is a highly productive ecosystem, which has an important economic role for riparian populations (fisheries, aquaculture, transportation, sand extraction, etc.) (Anoh, 2010; Kouassi et al., 1995). It also considered as one of the aquatic environment of Côte d’Ivoire most affected by anthropogenic activities as such domestic, industrial and agricultural waste dumping. These activities can accelerate the natural eutrophication and lead to dystrophic crises due to oxygen depletion (Bartoli et al., 2001) provoking mortalities in the benthic and fish communities, causing sometimes-irreversible deterioration of these ecosystems. The Benthic macroinvertebrates communities have an important role in the structure and functioning of aquatics ecosystems. Macroinvertebrates play an important role as the food source for diversity of fish, amphibians, birds, and other animals (Voshell and Reese, 2002; Tachet et al., 2010) and contribute substantially to the nutrient cycling, transformation of matter and energy flow in aquatics ecosystems (Tachet et al., 2010). They are direct contact with the sediment, where multiple contaminants tend to accumulate (Pilo, 2011) and have best respond to changing environmental conditions (Benoit-Chabot, 2014). To this fact, benthic macroinvertebrates have been extensively used for the assessment of the ecological integrity and biomonitoring of aquatic habitats (Beauger, 2008). Due to their limited mobility, benthic organisms are sensitive to local disturbance and because of their permanence over seasons, they integrate the recent history of disturbances that might not be detected in the water column (Warwick, 1993). The distribution of the different benthic Citation: Saki Yao APPIAH et al. Ijsrm.Human, 2017; Vol. 7 (4): 149-169. 150 www.ijsrm.humanjournals.com macroinvertebrates communities is considered one of the important indicators of the surface waters quality (Badea et al., 2010; Kubosova et al., 2010; Simmou et al., 2015). In Côte d’Ivoire, previous studies on benthic macroinvertebrates have been mainly performed in Aby lagoon (Kouadio et al., 2008), and Ebrié lagoon (Zabi, 1982; Sankaré and Etien, 1991; Le Loeuff & Zabi, 1993; Kouadio et al., 2011, Allouko et al., 2016). The purpose of the present study was to know the variability of benthic macroinvertebrate structure and to identify the abiotic variables managing the structure and the functioning in the sectors IV and V of Ebrié lagoon. 2. MATERIAL AND METHODS 2.1 Study area The Ebrié lagoon (Figure 1) is located between 5°13’ and 5°19’ N and 4°14’ and 4°27’ W. It is the largest lagoon (566 km²) of Côte d’Ivoire stretching for 130 km east to west with a maximum width of 7 km (Albaret 1994, Durand and Guiral, 1994). Based on the hydroclimate, and on aquatic primary and secondary production in Ebrié Lagoon have been divided into six sectors (Durand and Skubich 1982). The permanent linkage with the Atlantic Ocean by the Vridi Channel produces typical estuarine characteristics, especially in sectors II to III, which are near the channel. Under the direct influence of both the Atlantic Ocean and the Comoé River outflow, these parts of the lagoon are seasonally variable and heterogeneous with salinity varying from 0 (rainy season) to 35 (dry season). Conversely, sectors IV to VI are oligohaline (salinity 0 to <10), relatively stable and homogeneous throughout the year (Durand and Guiral, 1994). In the sector I, water is all year round almost exclusively of continental origin in Aghien lagoon and by water with salinity < 9 all year round in Potou lagoon (Traoré et al., 2012). The Ebrié lagoons system is situated in a region under the influence of a subequatorial climate characterized by two rainy seasons, a short (October-November) and a long season (May-July); and two dry seasons, along (December-April) and a short season (August- September) (Kouadio, 2011). 2.2. Benthic macroinvertebrates samples and environment parameter measure The sampling stations were investigated monthly during 12 months from August 2015 to July 2016. Samples were collected using a Van Veen grabs (0.03 m2). At each station, ten samples Citation: Saki Yao APPIAH et al. Ijsrm.Human, 2017; Vol. 7 (4): 149-169. 151 www.ijsrm.humanjournals.com were collected for benthic macroinvertebrates analyses. Each sample was sieved in situ through a 1 mm mesh. The organisms retained by the sieve were fixed in formaldehyde 10 % solution for maintenance of the samples. At the laboratory, macroinvertebrates were identified to the lowest possible taxonomic level and counted using the following works: Fauvel (1923, 1927), Intès and Le Loeuff (1975), Durand and Lévêque (1981), Dejoux et al. (1981), Tachet et al. (2010). Figure 1: Map of Ebrié Lagoon showing location of the sampling sites (●) 2.3. Measurement of Environmental parameters During the investigation period, in situ, the hydrologic parameters (water salinity, temperature, dissolved oxygen (DO), pH, total dissolved solids (TDS) and electrical conductivity were measured monthly at depth intervals of 10 cm, using a multifunctional probe. A Secchi disc was used for water transparency measures. 2.4. Statistical analysis The species richness (S), the Shannon diversity index (H’) and the Pielou evenness index (E) were used to determine the assemblage’s structure of benthic macroinvertebrates community. The analyses were carried out using the sub-routine of Paleontological Statistics (PAST) Package version 2.41. The species occurrence percentage (% of ) was calculated using the following formula: % of = (Ni/Nts) ×100, with Ni = number of samples containing a given taxa i, and Nts = total number of samples collected. The % of was used to classify species following Dajoz (2000): % of ˃ 50: very frequent taxa; 25 ˂ % of ≤ 50: common taxa; %OF Citation: Saki Yao APPIAH et al. Ijsrm.Human, 2017; Vol. 7 (4): 149-169. 152 www.ijsrm.humanjournals.com ≤ 25: rare taxa. Redundancy analysis (RDA) was conducted by using the computer program CANOCO, version 4.5 in order to assess the relationships between water physical-chemical parameters and benthic macroinvertebrates species. KruskalWallis and ANOVA test were performed to test the effects of stations and seasons on physicochemical parameters and benthic macroinvertebrates diversity and abundance. A significance level of p < 0.05 was considered. Analyses were carried out using the software package Statistica version 7.1. To