Environmental heterogeneity determines patterns of abundance and distribution of aquatic organisms in small forested wetlands

Abstract

Abstract Small wetlands have a high conservation value due to their importance as biodiversity hot spots. Despite this, they are nowadays at risk due to global change variables. We surveyed a set of seasonal wetlands located in Andean Patagonian forests which are the less studied aquatic systems. The wetlands selected presented different degrees of human impact, and some of them were geographically close and others were faraway and insulated. We registered environmental variables and the diversity and abundance of common pond animals in each wetland. Wetlands were described performing a principal component analysis considering the environmental variables. The main explanatory variables were dissolved organic carbon, water color, total nitrogen, and depth of the wetlands. The diversity of the aquatic organisms was studied using the Shannon index, and the relationship between environmental variables and aquatic organism was analyzed using canonical correspondence analysis (CCA). The rotifers showed the greatest diversity in the zooplankton assemblage, and the trichopterans were the most diverse of the benthic groups studied. The CCA showed that different variables explained the distribution of zooplankton and caddisfly/amphibian larvae assemblages. Each wetland presented a particular assemblage of species, and shared few species among them. Despite the differences in human impact and geographical distance, none of these factors appears to influence the diversity of these wetlands. We postulate that the high environmental heterogeneity found in these wetlands drives the diversity and abundance pattern of the aquatic biota observed.