Ocean temperature drives a latitudinal gradient of nearshore fish predation

Warmer seas play host to higher rates of fish predation, according to a new study featuring replicated experiments conducted across two oceans and 115 degrees of latitude. The research reveals a temperature-dependent latitudinal gradient with greater predation intensity and stronger impacts in warm equatorial waters than the cooler waters at higher latitudes. The findings suggest that future climate warming may have a predictable influence on top-down control of nearshore marine communities. “Such broad-scale shifts in top-down control could have far-reaching consequences, given the key role of species interactions in maintaining ecosystem structure, diversity, biogeochemical processes and the provision of critical ecosystem services to human communities,” write the study’s authors. Species richness for many taxa is generally higher near the equator. Ecologists have long suspected that this biogeographical pattern is linked to the strength of species interactions, such as predation and competition, in low tropical latitudes. However, recent studies that encompass the large spatial scales and multiple habitats required to test such a hypothesis are limited and have provided conflicting empirical support for it. As a result, little is truly known about how predation affects prey community composition at large geographic scales, particularly across latitudinal gradients. This understanding could help inform patterns of biodiversity, ecosystem function, and resilience to climate warming. To test whether predation on seafloor marine communities is higher at lower latitudes, Gail Ashton and colleagues performed a standardized and replicated experiment at 36 sites along the Americas’ Pacific and Atlantic coasts that spanned 115 degrees latitude. The experiment, which measured three separate components of predation, evaluated the impact of fish and other large, mobile predators on sessile seafloor marine invertebrate communities. Ashton et al. discovered that marine predators have both higher consumption rates and stronger impacts on biomass and species composition of benthic communities in warmer tropical waters nearer to the equator. These effects declined with water temperature across latitudes. According to the findings, the observed trends in predation were more strongly related to water temperature than latitude, which could have potential implications for how marine ecosystems will respond to ongoing ocean warming.