Life at the extreme: aquatic invertebrates across environmental gradients in high altitude saline lakes of Central Andes (Argentina)

This study aimed to determine main community attributes -occurrence, abundance and diversity indices- of zooplanktonic and benthic invertebrates in ten saline lakes located between 3,009 and 4,577 masl in Central Andes (Argentina), and to analyze how environmental variables affect these attributes using multivariate techniques. Sampling campaigns were performed during the spring-summer season (October to April), between 2016 and 2018. The ordination techniques classified the lakes into low- to high-altitude, and hypo- to hyperhaline groups. A total of fifteen taxa of invertebrates were recorded (seven planktonic and eight benthic) and the assemblages presented low abundance, low species richness (S), low diversity (Shannon index, H) and high dominance (Simpson index, D). Zooplanktonic and benthic community attributes were highly variable across environmental gradients, with a general trend to exhibit higher taxa richness at lower salinity content. Altitude and conductivity partially explained the spatial distribution of the assemblages, with some taxa only found in high altitude lakes (Cladocera) or hyperhaline lakes (Ephydridae), whereas others were widely distributed across the gradients (harpacticoids copepods, Monhysteridae nematods). Further research conducted at a smaller intra-lake scale may contribute baseline ecological information on the biota of these fragile and yet understudied systems, currently exposed to increasing anthropogenic pressures.