The Importance of Ecological Networks in Multiple-Stressor Research and Management

Abstract

Multiple stressors are increasingly affecting organisms and communities, thereby modifying ecosystems' state and functioning. Raising awareness about the threat from multiple stressors has increased the number of experimental and observational studies specifically addressing consequences of stressor interactions on biota. Most studies measure the direct effects of multiple stressors and their interactions on biological endpoints such as abundance, biomass, or diversity of target organisms. This yields invaluable information for the management and restoration of stressed ecosystems. However, as we argue in our perspective paper, this common approach ignores a fundamental characteristic of communities and ecosystems, i.e., that organisms in ecosystems are interlinked by biotic interactions in ecological networks. Examples from the literature show that biotic interactions can modify stressor effects, transfer stressor effects to distant groups of organisms, and create new stressor interactions. These examples also suggest that changes in biotic interactions can have effects of similar or greater magnitude than direct stressor effects. We provide a perspective on how to include network characteristics and biotic interactions into analyses of multiple-stressor effects on ecosystems. Our approach can also make use of biomonitoring data produced with established and intercalibrated methods, and can combine it with novel metrics used to describe the functioning of ecosystems, such as trait information or stable-isotope measurements. The insights on network-mediated effects gained via the approach we propose can substantially increase mechanistic understanding of multiple-stressor effects, and in turn, the efficiency of ecosystem management and restoration.

Soil fauna diversity and chemical stressors: a review of knowledge gaps and roadmap for future research

“…Many ecosystem functions are the results of interactions between soil fauna and microbes, and between above‐ground and below‐ground organisms (Wardle et al 2004). Therefore, understanding ecosystem functioning responses to chemical stressors needs to consider multi‐trophic biodiversity and biotic interactions (Bruder et al 2019). In addition, it will not be possible to forecast future soil biodiversity and ecosystem functioning without accounting for multiple drivers of global change (Rillig et al 2019), including chemical stressors (Schaeffer et al 2016).…”

The case for research integration, from genomics to remote sensing, to understand biodiversity change and functional dynamics in the world's lakes

“…Despite the complexity of lake ecosystem dynamics (e.g., Bruder, Frainer, Rota, & Primicerio, 2019) we propose that there are distinct, idealized types of research method integration, which we term complementarities. Each of these cases assumes the presence of an underlying causal "truth," and together these cases frame a diversity of opportunities for interdisciplinarity in lake ecology.…”

“…We argue that any attempt to integrate across research subdisciplines, to tackle the "big questions" around how freshwaters respond to global change drivers, must be underpinned by a conceptual (causal) model that is, a series of hypotheses and assumptions regarding the perceived "true" mechanisms and states of the ecosystem phenomena of interest. This begins with the recognition that Despite the complexity of lake ecosystem dynamics (e.g., Bruder, Frainer, Rota, & Primicerio, 2019) we propose that there are distinct, idealized types of research method integration, which we term complementarities. Each of these cases assumes the presence of an underlying causal "truth," and together these cases frame a diversity of opportunities for interdisciplinarity in lake ecology.…”

Agricultural pressures impair trophic link between aquatic microorganisms and invertebrates

“…This process relies on a complex interplay between microorganisms and invertebrates where microbial conditioning of OM enhances nutritional value for invertebrates, while consumption of OM by invertebrates renders a diverse size range of dissolved and particulate OM that supports microorganism as well as filter-and deposit feeding invertebrates (Barlöcher, 1985; Graça et al, 1993; Graça, 2001; Wright & Covich 2005; Danger et al, 2012; Danger et al, 2012; Arce Funck et al, 2015; Vonk et al, 2016; Bundschuh & McKie, 2016). While most studies and monitoring efforts focus on diversity measures such as species abundances within a single trophic level, an explicit consideration of the complexity of interactions is now crucial to develop an in-depth understanding of aquatic food webs and its vulnerability to human activities (Hines et al, 2016; Schrama et al, 2017; Seibold et al, 2018; Bruder et al, 2019).…”