Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 Recent increases in environmental variability and human activity threaten unprecedented reorganization of marine assemblages. The northwest Atlantic coastal shelf ecosystem (NWACS) has had a long history of fishing and with the addition of global climate change, its communities face disturbances at multiple spatial and temporal scales. We sought to quantify trends in the spatial structure of coastal assemblages among four NWACS regions, and to relate these patterns to potential external factors. Yearly abundance-occupancy (A-O) models were developed for each community. We used ordinary least squares regression to quantify temporal variation in the interspecific A-O relationship. The slopes, intercepts and coefficients of determination of these regressions were used as indices to describe patterns of organismal density (OD), total space used (TS) and spatial heterogeneity (SH), respectively. We found that the strength of trends increased with latitude, coinciding with regional shifts in assemblage structure. There was also clear, although regionally variable, evidence for the effect of commercial landings, surface temperature and Gulf Stream position on community spatial utilization. Our results help characterize the impact of extrinsic factors on ecologically relevant metrics tied to density-dependence and resource partitioning. Additionally, our results highlight the complexity and variety of biological responses to disturbance, even for adjacent communities. Last Modified: 10/31/2013 Submitted by: Michael Frisk