Chironomids community along Salix sp gradient in a stream of NW Patagonia. Preliminary results

MONTES DE OCA, FERNANDA; MASSAFERRO, JULIETA; BLACKHALL, MELISA; FRANZESE, JORGELINA; RELVA, M. ANDREA

Esquel

Congreso; 9no Congreso Argentino de Limnología; 2021

CIEMEP CONICET

Chironomid(Insecta:Diptera) larvae from Chacabuco Stream, a lotic system located in the northernPatagonia steppe, was analyzed between December 2018 and March 2021. Sampleswere collected yearly during two hydrological (seasonal) periods: low water(spring) and high water (summer) periods. Four sites were selected forsampling: two, located in a disturbed area composed by non-native plants(mainly Salix sp) and two, located inan area surrounded by native species (Nothofagusantarctica, Discaria chacaye). Taxonomical and functional chironomiddiversity was examined and compared at different levels: between sites andbetween seasonal periods. Limnological and climatic variables were alsoanalyzed and were used to investigate potential drivers of the faunalcomposition. Benthic invertebrate communities was analysed to observe whetherthere were differences in aquatic insect community structure at spatial andtemporal scales. The results show that the abundance and diversity of chironomidswere higher during the summer or high water period. The group of chironomidsbelonging to “collectors” such as Parapsectrocladius(in part), Tanitarsini and Chironomus feeding group were thedominant in the Salix plots. Incontrast, “scrapers” such us Stictocladiusand Psectocladius, “collectors-gatherers”such as Orthocladius sp, and Smittia and “collectors-filterers” Parapsectrocladius were the feedinggroups observed in native vegetation plots. These results show that thestructure of native plants of the riparian areas provide particularmicrohabitat diversification, light conditions, organic matter supply, andother conditions, (related to the structure of the stream bed, patterns ofriver flow) (work in progress), which favors periphyton growth. Consequently,the appearance of other feeding groups such as scrapers, collectors-gatherers,collectors-filterers, and predators and a high chironomid taxa number. Incontrast, plots with the presence almost exclusive of Salix spp. showed a severe reduction of light conditions leading toa poor substrate for algal growth and impoverishing the general fauna abundanceand diversification.