Plankton interactions, their environmental determinants and biological/geochemical consequences in the southern Senegal cOastal LABoratory – SOLAB

Coastal oceans and the services they provide are socially, economically and environmentally essential, particularly for the populations that inhabit their shores. These regions are subjected to major anthropogenic stress from local origin but also as a consequence of global changes: upper ocean warming, deoxygenation, acidification, eutrophication, overfishing, and various pollutions (heavy metals, wastewaters ...). These disturbances can interact with each other, and spread/amplify in the ecosystem through modifications of key trophic interactions. To manage and anticipate the effects of these disturbances, marine environment monitoring and management tools are urgently needed. Unfortunately, in many coastal areas, scientific knowledge is insufficient to implement such tools.

This context is exacerbated in West Africa where marine resources play a vital socio-economic role, where they undergo major anthropogenic stresses and where the functioning of marine ecosystems receives only modest attention. SOLAB proposes to turn a sector of the southern Senegal shelf (SSUS) of approximately 200 km by 200 km identified as particularly favourable into a natural laboratory for the study of coastal ecosystems and trophic interactions. The overall objective of SOLAB is to improve our ability to predict and manage coastal ocean evolutions. Because of its pivotal role in marine ecosystems, plankton will be the focus of SOLAB research. The project will investigate its dynamics, diversity, structure and variability in the 3 adjacent eco-subprovinces making up the SSUS. Specifically, we seek to 1) understand how the plankton ecosystem responds to variability of its physical/biochemical drivers on scales from days to months in time, and from 1 to 100 km in space (finer physical processes will also be considered insofar as they contribute to trophic transfers); 2) clarify present-day impact of planktonic and abiotic environment variability at these scales on small pelagic fish (mainly sardinella spp which utilize the SSUC as a nursery area) and coastal shellfish; 3) take advantage of 1) and 2) to explore the possible SSUS ecosystem modifications as a result of global changes.

Our methodology relies on integrated multi-scale modelling and observations (in situ and satellite) with an emphasis on synoptic/submeso scales (from a few days to a few weeks and 1-10 km). The transitions periods between the upwelling and monsoon seasons when most of the Sardinella aurita stock migrates in or out of the SSUS will be of particular interest.

SOLAB combines a wide range of observation methods (satellites, field campaigns, instruments on long-term moorings,measurements by acoustics, optics, chemistry analyzes, metabarcoding). Based on these state-of-the-art observation activities, SOLAB is designed to contribute to the emergence of a new generation of coastal ocean numerical models of the coastal ocean (covering physics, biogeochemistry, plankton functional biodiversity) apt to model SPF life cycles with a realistic representation of their habitat and relationships to fine-scale biotic/abiotic environment.
By turning Southern Senegal into a laboratory for coastal ocean sciences SOLAB seeks to support West African societies in managing their marine environment and its future evolutions (e.g., by pursuing training activities carried out for several years by the consortium). It also more specifically seeks to contribute to the development of marine aquaculture, and provide the scientific foundations of the Senegal marine environment observatory in planning.