Leveraging 4-Dimensionally Mapped Ocean Biogeochemistry to Inform Species Distribution Modeling

MARY MARGARET STOLL (University of Washington) ABSTRACT: Understanding the drivers of animal migratory patterns in a four-dimensional (4D) ocean is essential for developing reliable species distribution models (SDMs) that support ecosystem-based management. Despite recent advances in biologging and monitoring technologies, many SDMs overlook dynamic, subsurface biogeochemical conditions that impose critical constraints on suitable habitat. The Biogeochemical Argo (BGC-Argo) float array has revolutionized our view of the 4D biogeochemical landscape, providing new perspectives on the linkages between species distributions and environmental conditions. To assess the utility of depth-resolved, biogeochemical information in SDMs, we leverage archival tagging datasets, mapped ocean biogeochemistry data products, and machine learning methods to examine the extensive migrations of North Pacific albacore tuna (Thunnus alalunga), a commercially important fishery species. Our SDM predicts habitat suitability with high skill across space and time using multiple 4D biogeochemical predictor variables that capture both environmental deterrents (e.g. oxygen limitation) and attractants (e.g. chlorophyll, particulate organic carbon). These conditions strongly impact albacore vertical distributions, influencing both seasonal shifts and large-scale migration patterns. While temperature is a key determinant of habitat suitability, our findings demonstrate that biogeochemical variables substantially expand or contract habitat beyond what is thermally suitable. In this study, biogeochemical predictors contract suitable habitat by more than 60% in winter and expand it by 25% in summer, emphasizing the influence of subsurface biogeochemistry in modulating habitat availability. This scalable framework can be applied to other taxa and regions, offering new avenues to improve bycatch avoidance, catch per unit effort estimates, and predictions of climate-driven habitat shifts.