Partitioning the impact of environmental drivers and species interactions in dynamic aquatic communities

Abstract

Temperate aquatic communities are highly diverse and seasonally variable, due to internal biotic processes and environmental drivers, including human-induced stressors. The impact of drivers on species abundance is supposed to differ fundamentally depending on whether populations are experiencing limitations, which may shift over the season. However, an integrated understanding of how drivers structure communities seasonally is currently lacking. In order to partition the effect of drivers, we used random forests to quantify interactions between all taxa and environmental factors using macrofaunal data from 18 agricultural ditches sampled over two years. We found that, over the agricultural season, taxon abundance became increasingly better predicted by the abundances of co-occurring taxa and nutrients compared to other abiotic factors, including pesticides. Our approach provides fundamental insights in community dynamics and highlights the need to consider changes in species interactions to understand the effects of anthropogenic stressors.

Experimental evidence for neonicotinoid driven decline in aquatic emerging insects

“…Inferring causality on the contribution of each of these and other drivers is challenging and is commonly addressed using large datasets that describe local population dynamics. Such approaches ( 4 , 12 , 15 ) contain a number of confounding factors that limit the understanding of individual drivers. As a result, studies addressing potential drivers of decline are often inconclusive because of their correlative nature, possible occurrence of confounding factors, and the fact that most data are local instead of global ( 4 , 10 ).…”

Spatial and temporal homogenisation of freshwater macrofaunal communities in ditches

“…This is not the result of dispersion of propagules from locations with reproduction to locations without reproduction as this would show similar decreases of spatial diversity. Instead, knowing that community regulation is increased by increasing food limitation (Cadotte & Tucker, 2017;Musters et al, in press), the decreasing dissimilarity is likely to reflect an increase in food limitation or decrease in food quality over time, which is particularly evident in ditches adjacent to bulb fields where a myriad of agricultural chemicals are applied (Hunting et al, 2016Vijver et al, 2017).…”

Ecosystem coupling: A unifying framework to understand the functioning and recovery of ecosystems

“…Despite these trophic cascades, it is often surprisingly hard to pinpoint how disturbances, such as those from anthropogenic stressors, affect simple metrics of change, such as alpha diversity, abundance, or overall structure and functioning of freshwater systems. 100,101 Therefore, improved characterization of spatial and temporal coupling metrics in aquatic environments may aid in understanding how dynamic shifts, such as those imposed by anthropogenic stressors, affect the functioning of entire aquatic systems. This requires extensive efforts to monitor the biotic, abiotic, and biogeochemical components of freshwater ecosystems in both a spatial and temporal manner.…”