Relationships between the spatial distribution of oligochaetes (Annelida, Clitellata) and environmental variables in a temperate ESTUARY SYSTEM OF SOUTH AMERICA (RÍO DE LA PLATA, ARGENTINA)

ARMENDÁRIZ, L.C; RODRIGUES CAPÍTULO, A.; AMBROSIO, E. S.

NEW ZEALAND JOURNAL OF MARINE AND FRESHWATER RESEARCH

RSNZ PUBLISHING

Lugar: otago.ac.nzealand; Año: 2010

0028-8330

Abstract             We sampled the oligochaete assemblages on the Argentine coast of the Río de la Plata estuary seasonally (September 2005 through July 2006) within environments having different types of disturbances. Three habitats were sampled: sediments free of vegetation, sediments within bulrush stands, and substrates with the presence of the invasive mussel Limnoperna fortunei. The species richness, the evenness, and the Shannon-diversity values were different among those three habitats. The only dominant species (rated according to the Kownacki index) was Nais variabilis. The mean-density values varied between 400 and 199,500 ind.m-2. The organic matter, ammonium, and phosphates were positively correlated with the mean oligochaete abundance, but not with the granulometry. The physicochemical variables and nutrient levels were measured and their relation to the sampling sites assessed through a principal-components analysis (at a 41.8% cumulative variance). The canonical-correspondence analysis (at a 41.2% cumulative variance) indicated that the oligochaetes distributed along both a eutrophication and pollution gradient (axis 1) and a turbidity and conductivity gradient (axis 2). These results would be useful for assessing the ecological status of the estuaries for a subsequent implementation of the appropriate sustainability-management policies.