Decadal‐scale regional changes in Canadian freshwater zooplankton: the likely consequence of complex interactions among multiple anthropogenic stressors

Abstract

Summary Ecological integrity is increasingly threatened by multiple anthropogenic stressors, but the cumulative impact of stressors is poorly understood because they can interact in unexpected ways. Knowledge of these interactions and their associated impacts is needed to support the conservation of valued ecosystems. We used a large‐scale, replicated field survey and multiple regression analysis to investigate the cumulative impacts of multiple physical, chemical and biological stressors on the crustacean zooplankton assemblages of 34 Canadian Shield lakes between 1980s and 2004–2005. Zooplankton total abundance, species richness, diversity and community structure, as well as the relative abundances of prominent taxonomic orders of zooplankton, changed at a regional scale. These changes occurred in response to changes in water quality and lake thermal regime, and invasion by an exotic predator. Interactions between stressors were common and represented an important determinant of zooplankton assemblage changes over time. We provide the first evidence that the individual and combined impacts of multiple stressors cause regional ecological change over decades. Our results demonstrate the prevalence of stressor interactions in natural environments and highlight the complexity of ecosystem responses to multiple stressors. Zooplankton changes recorded here may be widespread because climate change, acidification, development and the spread of invasive species are globally pervasive. These changes could have cascading impacts because zooplankton is an essential link in aquatic food webs. Our findings highlight the need to consider the interactive effect of stressors when assessing anthropogenic impacts and will inform management and conservation of ecosystems threatened by multiple stressors.

Zooplankton community structure along a pollution gradient at fine geographical scales in river ecosystems: The importance of species sorting over dispersal

“…Local physicochemical factors and biotic constrains have been documented to affect zooplankton communities (Bertani, Ferrari, & Rossetti, ; Palmer & Yan, ). Consistent with our results, many studies demonstrated that the nutrient concentration change was the major driver for spatial variation in zooplankton community structure (Parkes & Duggan, ; Xiong et al., ).…”

The jellification of north temperate lakes

“…We tested our second hypothesis using two datasets: a longitudinal study of eight Ontario lakes sampled over a 30-year period [34], and a regional survey of 31 other Ontario lakes sampled in the 1980s and 2004 or 2005 [35] (see electronic supplementary material, table S2). Zooplankton were sampled during the icefree season near the point of maximum depth by using a metered, 76 mm mesh, tow net.…”

Landscape level estimate of lands and waters impacted by road runoff in the Adirondack Park of New York State

“…As mentioned above, road runoff pollutants often share similar environmental impacts as other regional stressors and often act synergistically, enhancing their effects on ecosystem function (Palmer and Yan 2013). A solid understanding of the spatial extent of road runoff stress allows researchers to focus regional monitoring efforts as well as develop study designs for experiments investigating the interactions of our significant regional stressors (Fancy et al 2009).…”

“…This large rural landscape is exposed to multiple environmental stressors operating at varying spatial scales and often in interacting ways that are poorly understood (Allan 2004;Palmer and Yan 2013). Historically, the principal environmental stressors studied in the region have been acid deposition and climate change (Ito et al 2002;Stager et al 2009).…”