Global change has consequences on marine populations but also less studied effects on the health status of biological communities. All of these changes affect the functioning of food webs and thus the production of goods and services for human communities. Recent studies show that global change is leading to a reduction in the production of long-chain omega-3 fatty acids (omega 3) at the base of the marine food web by altering the assemblages of microalgae and their physiology. These omega-3s play a vital role in maintaining the physiological functions of higher organisms since they are the main components of their cell membranes. This decline in omega-3 production at the base of the marine food web should mechanically have a cascading effect on the availability of these nutrients to primary and secondary consumers, such as exploited marine fish, which are almost incapable of synthesizing them. However, fish are one of the main omega-3 sources for humans, in whom the beneficial effects of these fatty acids have been widely demonstrated. This chain of consequences could therefore also lead to a possible decline in the availability of these fatty acids for human populations.
Mugilids are opportunistic fish that occupy a diversity of habitats and tolerate a wide range of environmental conditions. They generally occupy an intermediate position in coastal tropical networks: they browse the microalgal biofilm, and are consumed by other exploited fish species (e.g. sea bass, lean fish). They therefore play a key role in aquatic ecosystems by providing a significant part of the coupling between bottom trophic compartments and those of the water column. They thus contribute to the transfer of omega-3s to humans.
Laboratory studies have shown that the physiological performance and behaviour of mugilids (e.g. respiration, swimming performance, growth) are altered in response to a decrease in omega-3 food quality combined with an increase in water temperature (e.g. Vagner et al., 2014, 2015, 2019).
The objective of the project will be to explore the consequences of such modifications on the functioning of coastal marine food webs and, more particularly, on the efficiency of omega-3 transfer to the upper links, particularly to exploited fish and humans. The food webs associated with different types of habitats similar to those along the coast of Brittany will be analyzed. A detailed analysis of the results with regard to the socio-economic context of Brittany will also be proposed. The fishing and aquaculture sectors, which are vital in the region, will benefit from the development of knowledge on the “interest for human health” of mugilids in order to promote these products, particularly by canning factories.
From a methodological point of view, this multi-scale collaborative project between physiologists and modelers will develop an innovative numerical approach, coupling individual physiological data with existing coastal marine food web models (e.g. Linear Inverse Models) in the form of analysis of sensitivity of model parameters.