Structure and composition of Chironomidae (Diptera) assemblage in Ventana Stream (Argentina): a preliminary approach

SIRI, AUGUSTO; SPACCESI, FERNANDO; DONATO, MARIANO

San Carlos de Bariloche

Congreso; VIII Congreso Argentino de Entomología. Los Insectos y el hombre: diversidad de interacciones, diversidad de miradas; 2012

Sociedad Entomológica Argentina

A seasonal and bi-annual study on the structure and composition of Chironomidae assemblages on the Ventana Stream, Buenos Aires province (Argentina) is being conducted. Preliminary results of the samplings carried out in May 2011 are presented. Three sample sites were chosen along 12 km of this aquatic ecosystem: site 1 in the upstream section (782 masl), site 2 in the middle section (574 masl) and site 3 in the downstream section (342 masl). Different samplers were used: Ekman drag, D-net, and pipet. Univariate analysis was applied (taxa richness, Shannon & Wiener diversity, and Pielou‟s evenness). Physicochemical variables were measured to describe water quality. The pH had neutral values, conductivity had very low values (78-133uS/cm), percentage of dissolved oxygen increased from site 1 to 3 (75 to 85%), and the temperature had a mean of 13°C. A total of 4 subfamilies were recorded, Orthocladiinae with 3 genera, Chironominae with 3 genera, Tanypodinae with 3 genera, and Podonominae with 1 genus. The last subfamily represents the first record for Buenos Aires province. Site 1showed the lowest richness and diversity. Site 2 and site 3 showed similar richness and diversity, however the subfamilies composition varied. The Orthocladiinae was the dominant subfamily in site 2, followed by Tanypodinae and Podonominae. Conversely, Chironominae was the dominant subfamily in site 3, followed by Orthocladiinae and Tanypodinae.