The invasive polychaetes reef-forming Boccardia proboscidea outcompete engineering mussels

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

Mar del Plata

Conferencia; 2nd World Conference on Biological Invasions and Ecosystem Functioning (BIOLIEF); 2011

The study of the occurrence of invasive species through time and space can be useful to detect the native species outcompete. In the intertidal zone of Mar del Plata, Argentina (38˚S-57˚W), the invasive polychaetes Boccardia proboscidea is favoured by organic contamination generated by sewage discharge. The aim of this work was to assess the spatio-temporal pattern of the structuring species Brachidontes rodriguezii and the invader Boccardia proboscidea. Cover percent (0.25m2-squares) of both species and organic matter of sediments were sampled from 2004 to 2011 in four sites: Effluent and South Impacted (200m and 800m south of the outfall respectively), Control 1 (9,000m-north of the outfall) and Control 2 (8,000m-north of the outfall; from 2008). A repeated measures ANOVA was use considering 3 sample units in each site. Before 2008, B.rodriguezii percent cover reached values up to 80% in the Control site while in the impacted sites the values were lowest (30 - 50%). B. proboscidea had low cover in both Impacted and Control sites until June 2008. However, from June 2008 the percent cover of mussels largely decreases in impacted sites because the increase of B. proboscidea (almost 100% cover). The massive development of B.proboscidea resulted in biogenic reefs because the high increase in organic matter content of sediments. The effect of this polychaeta on the community structure is the displacement of the ecosystem engineer as structuring species.