Sewage-induced biogenic reefs build by indicator polychaetes in intertidal areas of the SW Atlantic.

JAUBET, M.L; SANCHEZ, M.A; RIVERO, M. S; GARAFFO, G.V; VALLARINO, E.A & ELIAS, R.

Montevideo, Uruguay

Workshop; ?Indicadores biológicos de contaminação de águas costeiras do sudoeste do Atlântico Países envolvidos: Brasil, Argentina e Uruguay.; 2009

The intertidal zone around Mar del Plata (38ºS-57ºW) is characterized by mussel beds of Brachidontes rodriguezii. The polychaete Boccardia cf. Polybranchia is associated to the intertidal community and has been identified as tolerant species to moderate-high levels of organic contamination due to sewage discharges. This is the first report of biogenic reefs built by a non-reef-forming spionid (Boccardia sp) in areas organically impacted by sewage discharges. The aim of this work was to evaluate the dynamic of these reefs along the months. Those structures were found during spring 2008 and covered it almost the entire impacted area with a density reaching 650,000 ind.m2. The reefs were ephemeral, disappearing from the most impacted sites and colonizing nearby locations in few days or weeks. The presence and stability of these reefs is discussed in relation to the increase of organic contamination and storm-induced disturbance as a structuring factor of these structures.