Assessing trait-based approach to long-term monitoring of soft-bottom macrobenthic assemblages in a polluted estuary

The use of biological traits analysis and functional diversity has emerged as a valuable tool for assessing anthropogenic impacts or disturbances on coastal communities. In this study, we applied this approach to evaluate the long-term variation in soft-bottom macrobenthic assemblages from 1998 to 2016 in the highly urbanized and industrialized Odiel-Tinto estuary. The assemblages were structured along the natural gradient from the estuary to the marine environment, although anthropogenic pressures, such as dredging and heavy metal contamination, played a decisive role in shaping functional composition. Functional indices, such as functional richness and Rao’s Q, proved to be more sensitive indicators of environmental changes than traditional taxonomic indices. In the inner zones, species richness and functional diversity were significantly lower, with communities dominated by small-sized opportunistic species typical of unstable environments. In contrast, the outer marine zones supported a more diverse range of feeding modes and functional traits. Traits related to body size, larval or egg development, feeding modes, and AMBI categories exhibited clear responses to environmental stressors, providing valuable insights into the resilience and recovery potential of macrobenthic communities. This study enhances our understanding of estuarine ecosystem responses to anthropogenic pressures and offers essential data for global estuarine conservation efforts, contributing to the formulation of management strategies applicable to similar environments worldwide. • Macrobenthic assemblages followed a clear gradient from estuarine to marine zones • Functional diversity indices were more sensitive than taxonomic indices • Inner estuarine zones exhibited low species richness and reduced functional diversity • Outer marine areas supported a wider diversity of functional traits. • Body size, feeding mode and pollution tolerance traits responded to stressors.