Effects of human-induced water level fluctuations on copepod assemblages of the littoral zone of Lake Maggiore

Abstract

Human-induced water level fluctuations (WLFs) are among the major pressures threatening lake ecosystems. Their effect on meiobenthic species of the littoral zone has been poorly investigated. In this study, we aimed at assessing the effects of human-induced WLFs on the composition and functionality of the benthic copepod assemblages of the littoral zone of Lake Maggiore, Italy and Switzerland. From 1942 to present, the water level of Lake Maggiore has been regulated through the Miorina Dam. We monitored copepod assemblages during different water levels defined within the period of regulation by the dam, using taxonomy- and trait-based metrics. We observed variation in the overall abundance and biomass of copepods, as well as in the number of individuals belonging to some trait classes such as ovigerous females, opportunists, omnivores and deposit feeders. None of the investigated trait class was completely lost. The results of our study suggest that ecosystem services supplied by the littoral zone of Lake Maggiore are likely altered by human-induced WLFs. Our findings provide a first picture of WLF impacts on benthic copepod assemblages, which can be useful for future research expanding on other functional traits.