Polychaete functional traits and environmental filtering on intertidal rocky shores in northwestern Morocco:...

Polychaetes are widely recognized as effective bioindicators of environmental conditions and anthropogenic disturbances in marine ecosystems. This study investigated seasonal and spatial variations in polychaete diversity and ecological quality across four rocky intertidal stations along the Atlantic shores of Safi (northwestern Morocco) over a 4-season period. A total of 25 species were identified, with Sabellaria alveolata being the most abundant (21 % of total individuals). The polychaete assemblages included five feeding modes, dominated by omnivores and filter-suspension feeders, particularly jawed omnivores, such as Perinereis cultrifera. Univariate indices (species richness, abundance, Shannon-Wiener diversity, and Pielou's evenness) revealed significant spatiotemporal variations, with the highest diversity recorded in spring. Stations closer to pollution sources showed lower diversity, highlighting the influence of environmental stressors on community structure. Multivariate analyses (PERMANOVA) identified significant differences in species composition, with deposit-feeding and opportunistic species (e.g., Capitella capitata) thriving in polluted areas, while filter-suspension feeders and sensitive species (S. alveolata) were more prevalent in less disturbed areas. Biotic indices (AMBI, M-AMBI, and BENTIX) reflected ecological quality ranging from "High" to "Moderate", with BENTIX being the most consistent in detecting degraded conditions. Environmental parameters such as salinity, dissolved oxygen, and pH significantly influenced community dynamics, emphasizing the value of integrating biological indices with environmental monitoring. This study highlights the role of polychaetes as reliable indicators for evaluating benthic ecological quality, underscores the importance of their functional traits in detecting anthropogenic impacts, and supports the development of targeted conservation strategies for intertidal ecosystems.