Macroinvertebrate assemblages in lowland streams under horticultural impact (Buenos Aires, Argentina)

Abstract

This study aimed to determine the impact of horticultural land use on the taxonomic composition and the composition of functional feeding groups of freshwater macroinvertebrate assemblages in lowland streams. Three streams running through intensively cultivated plots were compared to three less impacted streams, two of which run through a UNESCO Biosphere Reserve. Nutrient and pesticide measured concentrations, as well as the macroinvertebrate assemblages associated with aquatic vegetation, were analyzed in each stream. These concentrations were higher at the horticultural streams, negatively correlated to the richness, density, and diversity of the macroinvertebrate assemblages, leading to a dominance of tolerant families. The trophic structure of the macroinvertebrates assemblages was dominated by collector-gatherers in the horticultural streams, while all functional feeding groups were more equally distributed in less impacted streams. We concluded that horticulture reduces biodiversity and changes the trophic structure of the macroinvertebrate assemblage, eventually affecting stream functions. Mitigation measures are required to preserve the structure and function of these ecosystems.