Structure and Composition of Macroinvertebrates during Flood Period of the Nokoue Lake, Benin

Abstract

The Nokoue Lake is the largest lake of Benin Republic and it is also considered as one of the most productive lagoon ecosystems in West Africa. This productivity is decreasing and thus raises productivity issue for a better management and conservation. Macroinvertebrate can be useful for this purpose. A study was conducted to assess the spatial variation of macroinvertebrates during high flood period. A total of 3892 macroinvertebrates of fresh and brackish water were sampled during the survey. Structural analysis of the macroinvertebrate community revealed that it was made up of 16 orders, 48 families and 66 genera dominated by Insecta compared to Mollusca, Crustacea and the Annelida. Insects were dominated by Diptera (Chironomus sp. and Tanytarsus sp.), Coleoptera (Dystiscidae) and accounted for 57.1% of the sampled population. Mollusca, Crustacea, Annelida and Arachnida were the following most abundant and represented 23.9%, 10.7%, 8.1% and 0.2% of the total population, respectively. The Evenness index of Pielou was higher on the Station 8 (0.91-0.97), close to Oueme River. However, no significant difference (p > 0.05) was observed neither between station nor between month on the Shannon-Wiener index (2.06-4.31), Simpson index (0.04-0.40) and the taxa number (10-27). Macroinvertebrate assemblages and composition were primarily due to changes in water quality dependent on hydroclimatic changes and probably to anthropogenic actions. This suggests the need for real investigation of the macroinvertebrate biological capacity when formulating conservation strategies for the Nokoue Lake.

Comparison of aquatic macroinvertebrate communities of Lake Ahémé (Benin, West Africa) across the short and long wet seasons

“…The salinity gradient increased from north to south because of the Atlantic Ocean tidal influence (Amoussou, 2010; Badahoui et al, 2010; Dèdjiho et al, 2013). The same trend of variation was observed with conductivity, as reported by Odountan and Abou (2016).…”

“…This dominance order characterises most of brackish ecosystems as reported in Benin (Adandedjan et al, 2012) and elsewhere (Ajao & Fagade, 1990; Chaouti & Bayed, 2005; Zerga et al, 2003). However, these results are in contrast with Adandedjan et al (2011) in Porto‐Novo lagoon (Benin), Odountan and Abou (2016) in Lake Nokoue (Benin), and Imoobe (2008) in Ologe lagoon (Nigeria) who recorded insects as the dominant macroinvertebrate group. This different finding could be related to several factors, such as the difference in sampling methods/frequency or environmental conditions (e.g.…”

“…The former is characterised by two wet seasons with similar precipitation because of the proximity of the ocean (Planchon, 1996) which favours precipitation even during expected “short” wet season. This situation leads some ecologists to ignore the short wet season (SWS) and to consider one dry season and one wet season when studying the seasonal variation of aquatic organisms at Lake Nokoué and surrounding ecosystems (Adjagodo et al, 2017; Odountan & Abou, 2016; Zandagba et al, 2016, 2017). In some cases, the lack of evidence for differences in diversity and composition of macroinvertebrate assemblages between the two wet seasons justifies this monitoring strategy (Adandedjan et al, 2011).…”

Macroinvertebrate Communities in a Lake of an Inter-Basin Water Transfer Project and Its Implications for Sustainable Management

“…However, beyond all doubts, a lot of environmental, ecological and even social problems came after the water transfer projects [6]. Therefore, there is an urgent need to study and monitor the effects of water transfer projects with the aim of protecting aquatic ecosystems in a sustainable manner [7,8].…”

“…Furthermore, owing to technical and financial limitations, it is hardly conceivable to determine all possible pollutants occurring in sediment and to measure their concentrations [11]. Biological methods appear as an alternative to chemical detection using living organisms and have the advantage of being simple and easy to implement [8]. For the above reasons, it is necessary to carry out aquatic bio-monitoring for the lakes involved in water diversion projects.…”