Structure of intertidal benthic community in areas organically impacted of Mar del Plata, Argentina (SW Atlantic).

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

Lecce

Conferencia; 10th International Polychaete 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:TimesNewRoman; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:0; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:auto; mso-font-signature:3 0 0 0 1 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;} --> The intertidal zone around Mar del Plata, Argentina is characterized by dense mussel beds of the small mytilid Brachidontes rodriguezii established on natural or artificial hard substrates. The community also develops in sewage impacted areas on abrasion platforms being used for environmental impact assessment by sewage discharges, as well as their associated polychaetes. Organic enrichment of sediments due to sewage may result in a series of non-linear changes in the abundance, biomass and diversity of benthic organisms, in both spatial and temporal patterns. The polychaetes are one the most useful marine taxa for detection of pollution because they live at the water-sediment interface. The present study was carried out in the intertidal zone around Mar del Plata sewage effluent. The samples were collected during November-December 2008, and January- February of 2009 in two Control and two Impacted areas to assess spatial and short-term impact (Before-After Summer). Multimensional scaling (MDS) and Similarity Analysis (ANOSIM) were employed to evaluate differences between areas and before-after summer. Differences due areas are highly significant (R= 0.716, p 0.1%). Species that most contributed to differences are B. rodriguezii (dominant in Control areas) and Boccardia sp. (dominant in Impacted areas, but also subdominant in Control 2). Differences in Before-After Summer were not significant. The irruption of Boccardia sp. in the area produces a great change in the dynamics of the area. Impacted areas resulted almost permanently covered by the new Boccardia species, producing biogenic reefs. The monoculture of this polychaete outcompete all other species of the intertidal community. Microbiological and coprostanol analyses were employed to detect the influence of sewage in the spatial and before-after scale. However data from January and most of the environmental data are still under analysis.