Understanding how food web structure varies across broad spatial gradients is essential for identifying general principles of ecosystem organization and resilience under global change. We analyzed seven highly resolved marine food webs spanning a latitudinal gradient from 48°S to 78°S in the Southwest Atlantic and Antarctic region to evaluate how ecosystem size, latitude, human impact, and number of species shape network structure and dynamic stability. We quantified multiple topological and dynamical properties—including connectance, link density, mean trophic level, modularity, dynamic stability (maximum eigenvalue), SVD-based complexity, and rank deficiency—and modeled their relationships with environmental predictors using a multivariate Bayesian framework. To account for the variability of food webs, we implemented a metaweb assembly model by simulating site-specific local networks.
Ecosystem area emerged as the strongest and most consistent predictor of food web organization. Larger ecosystems supported higher trophic levels, greater interaction density, increased structural complexity, and higher dynamic stability, in agreement with theoretical expectations. However, larger areas exhibited lower modularity, which is consistent with large-scale fish food webs. Although lower modularity is often associated with greater potential for perturbation spread, the greater spatial extent of large ecosystems may buffer disturbance propagation at broader scales. Latitude showed similarly strong effects: higher-latitude systems exhibited greater connectance, structural complexity, trophic level, and dynamic stability, independent of the number of species. In contrast, human impact effects were comparatively weak and uncertain, likely because the cumulative impact index integrates multiple stressors whose effects on food web structure may differ in magnitude and direction.
Together, these results demonstrate that ecosystem size and latitude are dominant drivers of marine food web structure and resilience in the Southwest Atlantic.