Trophic Characterization and Ecosystem Modeling of An Artificial Reservoir in a Humid Tropical Zone: The Case of the Farm-school Lake at Jean Lorougnon Guédé University (Daloa, Côte d'Ivoire)

Small artificial reservoirs in humid tropical regions are increasingly influenced by agricultural activities, nutrient inputs, and organic matter, which can alter water quality and trophic functioning. Understanding the organisation of food webs and the pathways of energy transfer within such systems is essential for assessing their ecological functioning and supporting sustainable management. However, the trophic structure of the farm-school reservoir at Jean Lorougnon Guédé University has not been comprehensively characterised at the whole-ecosystem level. This study characterised the trophic organisation and energy-flow structure of the 0.065 km² farm-school reservoir at Jean Lorougnon Guédé University, Daloa, Côte d’Ivoire. Environmental and biological monitoring was conducted from December 2022 to February 2024, combining physicochemical measurements, fish sampling, stomach-content analysis, plankton sampling, benthic macroinvertebrate collection, and Ecopath mass-balance modelling. The reservoir food web was organised into nine functional groups encompassing ten fish species, primary producers, invertebrates, and the detrital bacterial compartment. The balanced model indicated a trophic structure extending to level 3.52, with phytophagous cichlids occupying a low trophic level (TL = 2.12) and contributing the highest fish biomass (24.50 t/km²). Their ecotrophic efficiency was 0.845, while apex and secondary carnivores depended substantially on this group in their diets. Phytoplankton and macrophytes supported both direct pelagic transfer and detrital recycling pathways, with benthic omnivores, microbenthivores, invertebrates, and bacteria contributing to the utilisation of organic matter. The hydrochemical conditions indicated mesotrophic-to-eutrophic characteristics, with conductivity ranging from 385 to 440 μS/cm, nitrate concentrations of 3.2–4.8 mg/L, mean BOD₅ of 38 mg/L, and surface oxygen of 6.4 mg/L. Overall, the reservoir functioned through closely connected pelagic and benthic pathways, highlighting the importance of water-quality management, riparian macrophytes, and agroecological practices for maintaining ecological functioning and supporting sustainable educational aquaculture.