How do aquatic communities respond to contaminants? It depends on the ecological context

Abstract

Recognizing patterns in nature and using these observations to generate and test hypotheses are fundamental components of scientific inquiry [1]. The science of ecotoxicology aims to identify patterns that describe population and community responses to contaminants. Our ability to predict these responses is generally greatest for communities that change consistently in response to a specific contaminant or class of contaminants, thereby providing a direct path to extrapolation, hypothesis testing, and scientific inference (see Predicting the Effects of Contaminants). Although evidence suggests that some communities respond similarly to both natural and anthropogenic stressors [2], we know that regional variation in how communities are composed as a result of environmental, historical, biogeographical, or climatic factors complicates our ability to identify general patterns. Several studies have reported that the effects of contaminants on populations and communities vary along environmental In This Issue: ET&C FOCUSFocus articles are part of a regular series intended to sharpen understanding of current and emerging topics of interest to the scientific community.Abstract-Context dependency refers to variation in ecological patterns and processes across environmental or spatiotemporal gradients. Research on context dependency in basic ecology has focused primarily on variation in the relative importance of species interactions (e.g., competition and predation) among communities. In this Focus article, the authors extend this concept to include variation in responses of communities to contaminants and other anthropogenic stressors. Because the structure of communities varies naturally along environmental gradients, their responses to contaminants may also vary. Similar to the way in which aquatic toxicologists assess abiotic factors associated with contaminant bioavailability, observations about context dependency could be used to test hypotheses about ecological mechanisms responsible for differences in sensitivity among communities. Environ. Toxicol.

Impact of contaminated-sediment resuspension on phytoplankton in the Biguglia lagoon (Corsica, Mediterranean Sea)

“…The main reason for this is that past experiments were mainly based on laboratory investigations typically performed under controlled conditions, from singlecontaminant tests, and without taking into account biotic and abiotic factors. Yet consideration of the environmental context has been shown to be essential to achieving a comprehensive understanding of the biological effects of contaminants (for reviews see Clements and Rohr, 2009;Clements et al, 2012). Phytoplankton responses to contaminants can, for example, be influenced by species interactions (Leboulanger et al, 2001;Ortmann et al, 2012), grazing pressure (Munoz et al, 2001), temperature (Bérard et al, 1999), water chemistry (Knauer et al, 2007), light exposure history (Guasch and Sabater, 1998;Laviale et al, 2010) or contamination exposure history (Dorigo et al, 2004;Serra et al, 2009).…”

Riverine Ecosystem Management

“…The assessment and prediction of chemical impacts in river systems are complicated by a range of context-dependent factors that act on different spatial scales (Clements et al 2012). Here, we focus particularly on factors that influence the impacts of chemicals in river systems on the site and landscape scales (Fig.…”

“…10) are also known to interact in their impact on freshwater organisms . Consequently, prediction of the impacts of a chemical in a river would require understanding of the interactions of chemicals with potentially co-occurring stressors or the environmental context in general (Clements et al 2012). This is highly relevant for risk assessment as it implies that the same chemical concentration can have different impacts depending on the context (Fig.…”

Assessing sediment toxicity: Past, present, and future

“…Bringing together the thoughts of many colleagues, I offer the following suggestions for improving the sediment assessment: 1) create a better linkage of spatial and temporal exposure with effects, thereby reducing uncertainty in hazard and risk assessments; 2) improve field method sensitivity, discriminatory power, and practicality; 3) use context-based assessments [24] that link key sensitive indigenous receptors with stressors; 4) consider ecosystem stress from habitat, nutrients, solids, and hydrology in the context of water column (baseflow and stormflow) and sediment contaminants; and 5) validate efficient biomarker relationships to population and community effects. Currently, the field of sediment ecotoxicology is addressing these issues, and noteworthy advances are more evident with each passing year.…”