The widespread footprint of demersal fishing, coupled with evolving environmental legislation, necessitates advanced frameworks to assess both the structural and functional dynamics of benthic ecosystems. Modern marine conservation frameworks increasingly demand assessment tools that go beyond structural changes, capturing also the functional degradation caused by bottom fishing. Here we applied a deterministic trait-based modelling framework, the Benthic Fishing Impact Assessment Tool (Bfiat), to quantify how fishing intensity, sediment type, and species life-history traits interact to shape benthic community state and ecosystem functioning.

Using macrofaunal data from 143 stations across a gradient of trawling disturbance off the Northern Sicily continental shelf, we estimated the benthic state (post-disturbance density divided by predicted carrying capacity; D/K) and recovery trajectories. We specifically focused on benthic communities, key functional groups (suspension and deposit feeders), and processes (bioturbation and bioirrigation) that play central roles in regulating sediment biogeochemical cycling. The most degraded benthic states (D/K<0.75) occurred in heavily trawled stations (Swept Area Ratio >3yr-1), which were largely dominated by surface-dwelling and shallow-burrowing species.

Conversely, an area closed to trawling for over two decades served as a crucial baseline; here, observed densities closely approximated the local carrying capacity, illustrating an environment with minimal fishing pressure. Furthermore, species identified as lower D/K outliers, such as the polychaete Sternaspis scutata and the bivalve Nucula nucleus, displayed greater variability, suggesting a potentially higher sensitivity when subjected to cumulative environmental stressors. Functional declines in suspension feeding, bioturbation, and bioirrigation closely mirrored the overall structural degradation. Ultimately, this study demonstrates the critical value of integrating functional and structural indicators to provide a more comprehensive, species- and habitat-specific risk assessment of demersal fishing impacts on benthic ecosystems.