Sewage-induced polychaete reef in the SW Atlantic: a phenomenon nothing ephemeral, they arrive to stay permanently.

JAUBET MARÍA LOURDES; MARIA DE LOS ANGELES SANCHEZ; GRISELDA VALERIA GARAFFO; MARIA SILVIA RIVERO; EDUARDO ALBERTO VALLARINO; RODOLFO ELÍAS

Lecce

Conferencia; 10th International Polychaeta Conference; 2010

<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-1610611985 1073750139 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; text-align:justify; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-fareast-font-family:Calibri; mso-bidi-font-family:"Times New Roman"; mso-fareast-language:EN-US;} span.mediumtext {mso-style-name:medium_text; mso-style-unhide:no;} span.shorttext {mso-style-name:short_text; mso-style-unhide:no;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; mso-ascii-font-family:Calibri; mso-fareast-font-family:Calibri; mso-hansi-font-family:Calibri;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Intertidal areas around the sewage outfall of Mar del Plata city (32°S-57°W) have been studying since 1997. The community, characterized by the mussel Brachidontes rodriguezii, as well as their associated polychaete fauna have been successfully used to assess organic contamination. The spionid Boccardia polybranchia has been identified as tolerant species to moderate-high levels of organic contamination due to intertidal sewage discharges. Hence a study of their population dynamics started at the beginning of 2008. However, during spring 2008 other (invasive?) Boccardia species colonized the sewage-impacted area forming biogenic structures like reefs. These massive reefs occupied all the rocky intertidal (horizontal abrasion platforms) up to 2,000m around the outfall. These structures were constituted by vertical tubes of polychaetes, in densities up to 650.000 ind.m-2. The sediment seems to be binding by mucus, providing great stability to the reef and make it compact enough to support a person walking over. First studies showed the ephemeron nature of these reefs, because their destruction and regeneration occurred in just few weeks. However, they survive the storm effect (autumn-winter of 2009) and nowadays are permanent structures. The aim of this work was evaluate the recovery time of the reef to an experimental disturbance of small scale. The present study was carried out on one impacted area situated 1000m south of the sewage effluent of Mar del Plata city. Five rocks were selected randomly and the recovery to a small-scale disturbance (39 cm-2) was evaluated. Posterior successive days to the disturbance, each rock was sampled to measure the density of the patch. Preliminary results have shown that the total recovery of the reef has been as fast as 3-4 days.