Ocean Currents and their Influence on Marine Food Webs and Biodiversity

Ocean currents are essential for the functioning of marine ecosystems, impacting the distribution of heat, the cycling of nutrients, and the interrelationships between habitats located throughout the global ocean. Although the ecological importance of ocean currents is being increasingly recognized, there is currently a lack of synthesis of the mechanistic links between the oceanographic processes related to currents and the often-polarised diets and biodiversity distributions of marine food webs. This paper uses an integrative approach to examine the influence of the major ocean current systems (Benguela, California, and Arctic boundary) on primary productivity, trophic structure, and species diversity along the lengths of different oceanic environments (e.g., continental shelf versus the open ocean). The approach is based on the integration of satellite-derived sea surface temperature and chlorophyll-a data, in situ sampling of stratified transect stations, stable isotope analyses (δ¹³C and δ¹⁵N), and Ecopath with Ecosim (EwE) modeling of food webs to characterize the trophic pathways and indices of biodiversity in upwelling zones compared with non-upwelling zones. The results of this study demonstrate that ocean current-induced upwelling has generally increased the biomass of phytoplankton (mean chlorophyll-a concentration: 4.2 ± 0.9 mg m⁻³) and resulted in food webs with a higher mean trophic level (MTL: 3.8 ± 0.4) than in oligotrophic gyres (mean chlorophyll-a concentration: 1.1 ± 0.3 mg m⁻³; MTL: 2.9 ± 0.3). Additionally, the Shannon indices of diversity were significantly higher in the upwelling zones (H' = 3.21 ± 0.18) than in non-upwelling areas (H' = 2.04 ± 0.22). The results illustrate that ocean circulation is critically important for the maintenance of marine biodiversity and food web integrity. The findings are highly relevant to the development of marine conservation planning.