Study of Planktonic Food Webs in the Mayotte Lagoon: Towards Adaptive Ecological Monitoring in the Face of Anthropogenic Pressures

Mayotte, a tropical French island located in the northern part of the Mozambique Channel in the western Indian Ocean, boasts a unique lagoon housing a diverse marine ecosystem that is particularly sensitive to anthropogenic pressures. At the heart of this ecosystem lies the planktonic food web. Plankton, including phytoplankton and zooplankton, support the biological production of many habitats, such as coral reefs and seagrass beds, by providing the main source of carbon and nutrients for higher trophic levels. However, this vital food web is under increasing pressure, such as eutrophication, caused by nutrient inputs linked to human activities.
To assess the health of this ecosystem and monitor its response to pressures, it is crucial to develop indicators targeted at the planktonic food web. The typology of this food web enables us to better understand how plankton, the base of the food chain, reacts to environmental changes, in terms of carbon production and energy transfer. For example, phytoplankton, which vary in size and abundance according to nutrient concentration, directly influence the trophic chains that depend on them, and the availability of carbon for higher levels.

Ecological network analysis (ENA) is a valuable tool for quantifying the structural and functional properties of these planktonic food webs. By examining carbon transfer pathways, this method can identify key indicators such as food web stability, nutrient recycling capacity and planktonic community productivity intensity. Thus, in more nutrient-rich waters, the food web may become more active but less stable, while in less productive environments, the food web tends to be more organized and resilient.
The integration of planktonic food web typology and ENA indices provides an effective framework for adaptive management of the Mayotte lagoon. By closely monitoring planktonic responses to anthropogenic pressures, this approach helps to better orient conservation strategies, thereby preserving the ecological balance of this exceptional lagoon.