Massive polychaete reefs as indicator of both increase sewage-contamination and chlorination process: Mar del Plata as a case not of study

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

Simposio; International Symposium on Outfall Systems (ISOS); 2011

<!-- /* 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;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES; mso-fareast-language:ES;} .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;} @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;} --> Sewage discharge is one of the oldest forms of contamination. To assess the effect of contaminants on the environments the use of biological indicators is recommended, because the organisms could show the healthy of the environment. Mar del Plata has the worst scenario for a sea side resort: the sewage effluent discharge untreated on intertidal zone affecting most of the coast line. Benthic studies on intertidal community were conducted since 1997. The intertidal community, dominated by the small mytild Brachidontes rodriguezii, develops on almost horizontal, abrasion platforms of consolidate sediments. Mussel beds form a secondary infaunal habitat for several invertebrate fauna, including several species of polychaetes. Polychaetes have been recognized as tolerant or sensitive to contamination, been useful for indexes to environmental health monitoring. The objectives are assessing the effect of the sewage discharge in the spatial and temporal scale. The samples were collected from November 1997 to November 2008 in the intertidal community developed in both Impacted and Control sites. For the analysis three areas were considered by pooling data from the Impacted site (between 50-200 m south to the sewage effluent), the site called Control 2 (between 800 to 1,200 m south to the effluent), and the Control site (an area 9,000 m north to the effluent). A total of 64,723 individuals belonging to 27 polychaete species (11 families) were recorded from 1997 to 2008 in the intertidal reference areas and those affected by sewage discharges. The Analysis of Similarity (ANOSIM) show significant differences (Global R= 0.116, p 0.2%), been all groups different from each other (RImpacted, Control 2= 0.059, p 4.3%; RImpacted, Control= 0.171, p 0.2%; RControl 2, Control= 0.123, p 0.4%). The SIMPER analysis show the species that most contributed to the differences among sites by pooling the years analyzed. The sewage-impacted areas are characterized by the capitellid Capitella “capitata” sp. and the spionids Boccardia spp. and B. proboscidea. The later (an invasive species) produce a bloom from 2008, developing biogenic structures. These reefs reached abundances several orders of magnitude greater in response to increasing organic contamination. The Control 2 area is characterized by high abundances of the spionids but also by Leodamas uncinata and Syllis prolixa. The Control site have the same polychaetes species, but in lower abundances. From 2003 the site name Control 2 (1,200 m south to the effluent) behaves as a permanent sewage-impacted location. The data strongly suggest that the explosive development of polychaete reefs was trigged by the progressive increasing of sewage-contamination. The disappearance of the reefs in February is also highly correlated to the chlorination process of sewage, and the release of chlorinate water to the environment. Mitigation process kills both the invasive polychaete reef and natural fauna.