Ward, Colette L.; Hunsicker, Mary E.; Shelton, Andrew O.; Hollowed, Anne B. 2019. Spatial community structure of groundfish is conserved across the Gulf of Alaska. (Abstract)
The mechanisms structuring patterns of diversity and community composition can be difficult to identify in large, open ecological systems. However, it is important to understand what drives these patterns at larger scales, especially in the face of climate change and other perturbations. The Gulf of Alaska (GOA) is an ideal study system because it has complex topography, climate-driven variability, and an on-going groundfish community survey. We used groundfish community data to examine the ecological theory underlying spatial diversity and community composition across 10 study areas in the GOA. We created geostatistically modeled groundfish abundance and biomass from the Alaska Fisheries Science Center trawl survey data (1984 to 2015) to address inherent errors in trawl observations. We found that species richness and alpha, beta, and functional diversity varied little both within and between study areas. However, turnover in community composition was significant along a longitudinal gradient, with differences driven by lower-abundance species. Fishing pressure had non-linear effects only on species richness and local diversity, while productivity was linearly related to beta diversity. We conclude that spatial patterns of diversity were not driven by disturbance, but were largely driven by environmental heterogeneity, because of the longitudinal turnover in community composition and high beta diversity (and thus low saturation). In addition, the invariant functional diversity but varying community composition together indicate functional redundancy in this ecosystem. Finally, the spatially invariant alpha and functional diversity show that the underlying community structure of the GOA groundfish community was conserved across this large marine ecosystem.