Anthropogenic environmental changes impact freshwater biodiversity globally. While biodiversity assessments in freshwater environments have traditionally focused on individual groups of organisms or trophic levels, considering patterns of ‘multitrophic biodiversity' across the food web provides a more comprehensive view of anthropogenic impacts and changes in communities along environmental gradients. Here we evaluate spatial biodiversity patterns in multitrophic communities of lake plankton (bacterioplankton–phytoplankton–zooplankton) across a lake‐rich country: Canada. Capitalising on the first standardized survey at the country scale, we used random forest and structural equation models to identify natural and anthropogenic drivers of multitrophic alpha and beta diversity in 559 lakes from 11 ecozones. Our analyses revealed that multitrophic alpha diversity (assemblage richness) was positively related to water quality but negatively related to water clarity, while beta diversity (assemblage uniqueness) was negatively related to both water quality and water clarity. Agricultural land use in lake watersheds strongly affected water quality and clarity, thus indirectly shaping multitrophic alpha and beta diversity. Bacterio‐, phyto‐ and zooplankton diversity were not well correlated and responded to distinct drivers, confirming the utility of multitrophic indices to provide an integrative view of diversity patterns. Finally, our analyses showed that facets of alpha and beta multitrophic diversity have contrasting responses to the indirect effect of a key human disturbance, watershed land use, thereby illustrating the value of considering multiple diversity facets in biodiversity assessments.
Fugère et al. (Thu,) studied this question.