A comparative study of the Ébrié lagoon (Ivory Coast) and Lake Nokoué (Benin) was made based on ecotrophic model outputs that describe each system's structure and functioning. Two models were constructed using the Ecopath software to differentiate main biomass flows in the systems.Results indicate that biomasses and productions in both ecosystems are concentrated in trophic levels (TL) 2 and 3. Higher TL biomasses and productions in Lake Nokoué compared to Ébrié lagoon may be explained by the presence of acadjas. High production per biomass (P/B) and food consumption per biomass (Q/B) values indicate the high productivity of these systems and the abundance of juveniles in most groups which utilize these systems as refuge zones and nurseries. The difference, however, lies between the principal source of energy and how it is incorporated in the food web of each ecosystem. Lake Nokoué is a detritus-driven ecosystem while Ébrié lagoon is dominated by the phytoplankton pathway. System indicators suggest different levels of ecosystem stability and maturity. Relevance of other observations on ecosystem functioning and indicators in relation to perturbation is discussed.

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The macroinvertebrate, assemblage investigated were collected in eight seasonal samplings from July 2007 through June 2009. A total of 4,179 individual macroinvertebrates were gathered, comprising 182 taxa belonging to 25 orders and 114 families. The most predominant groups were Molluscs and Crustacean which make up 71.11% of the taxonomic richness observed. Annelids and Insects were the second most predominant. This restricted biodiversity is based on a limited number of species such as Tympanotonus fuscatus radula, Pachymelania aurita, Neritina glabrata, Corbula sp., Clibanarius spp., Grandidierella africana, Nereis sp. and Chironomus sp.. Site typology based on environmental parameters reveals five assemblages in which no significant difference exists. The community is controlled by a salinity gradient but is also probably affected by hydrologic factors and human economic activities.