The immensity of the oceans makes it difficult to monitor them at a spatio-temporal scale that is relevant for resolving ecological processes and responses to decades of pressure from multiple anthropological stressors. With IsoMod, I aim to map the biogeochemical tracers at the base of the food web to inform three key measures of marine ecosystem processes that might be affected by these stressors: productivity, food web structure and animal migration pathways. The application of these tracer maps will be showcased in two case studies. The first will test the role of environmental changes in Atlantic puffin (Fratercula arctica) winter diet in key life-history parameters. Due to a general decline of the population size observed since the early 2000’s, the International Union for Conservation of Nature (IUCN) upgraded its status to "vulnerable" in 2015. The second case study will use the tracer maps to improve forecast of Northeast Atlantic mackerel (Scomber scombrus) summer distribution by identifying best foraging conditions for the fish ahead of their migration to the summer feeding grounds.
Conclusions:
Beyond the production of tracer maps that were made available publicly, ISOMOD demonstrated the usefulness of the approach by identifying strong inter-individual variability in molting grounds and diet within a same colony of puffins in the North Atlantic. This type of information is crucial to understand better the demographic evolution of the seabird populations and develop appropriate conservation measures. The results from the action will lead to the development of further applications for a wide range of marine animals (other seabird species, salmons, marine mammals, sea turtles...).
