Estuarine seaweeds as sinks of anthropogenic particles

Recent studies have shown that seaweeds are significant sinks for emerging contaminants such as hazardous anthropogenic particles (APs). The Bahía Blanca Estuary-BBE (Argentina; S38°44’ – 39°27’; W61°45’ – 62°30’) harbors one of the major port complexes of the Southwestern Atlantic Ocean, with intense maritime traffic and significant economic activities. The seaweed flora of the BBE, formerly considered poor (10 taxa) now comprises 22 taxa, due to the increased availability of artificial substrate and introduction of exotic species. The aim of this study was to evaluate the abundance of APs in different seaweed taxa. Seaweeds were collected at four sites with different anthropogenic influence, representing approximately 50% of the local flora, including four Classes: Florideophyceae (Polysiphonia morrowii and Ceramium diaphanum); Bangiophyceae (Porphyra sp. and Bangia sp.), Phaeophyceae (Punctaria latifolia and Planosiphon nakamurae), and Ulvophyceae (Ulva linza, Ulva flexuosa, Ulva lactuca and Blidingia minima). These taxa are the most frequent in the austral winter at the BBE and exhibit different thallus morphologies (i.e. filamentous, laminar, tubular, compressed). APs were extracted, identified and quantified according to established protocols and categorized based on morphology, color, and size. Seaweeds proved to be effective sinks for microplastics (MPs), antifouling and anticorrosive paint particles (APPs), burnt black particles, metallic fragments and black microspheres. APs (total= 160) were detected in all the taxa studied, being MPs the most abundant type (48.13%). P. nakamurae, showed the highest MPs abundance (1.576 ± 0.197 items g⁻¹ w.w.). Ulvophyceae exhibited the greatest diversity of particle types, including various morphotypes of MPs, APPs, and items classified as “other”, the latter being detected exclusively in Ulva. In contrast, Phaeophyceae, Bangiophyceae and Florideophyceae accumulated only microfibers and MPs. No significant differences were detected in MPs' concentrations among thallus morphology (p>0.05); however, retention capacity differed among sampling sites, reflecting local pollution sources.