Global warming and potential shift in reference conditions: the case of functional fish-based metrics

Abstract

The reference condition approach, advocated by the Water Framework Directive, is the basis of most currently used multimetric indices using functional traits of fish species. The ecological status of streams is assessed by measuring the deviation of the observed trait values from the theoretical values of reference conditions in the absence of anthropogenic disturbances. While reference conditions serve as baselines for ecological assessment, they vary with natural environmental conditions. Therefore, global warming appears to be a major threat to the use of current indices for diagnosing future stream conditions, as climate change is projected to modify assemblage composition, suggesting that the functional structure of fish assemblages will also be affected. The main objectives of this study are to assess the potential effect of climate change on the trait composition of fish assemblages and the consequences for the establishment of reference conditions. The results highlight the relation between environmental, especially climatic, conditions and functional traits and project the effects of climate change on trait composition. Traits based on species intolerance are expected to be most negatively affected by the projected climatic shift. The consequences for the development of multimetric indices based on fish functional traits are discussed.

The influence of riparian vegetation shading on water temperature during low flow conditions in a medium sized river

“…Stream water temperature is an important and limiting parameter for a number of organisms such as fish or aquatic invertebrates (Broadmeadow and Nisbet, 2004;Matulla et al, 2007;Rahel and Olden, 2008;Logez and Pont, 2013;Pletterbauer et al, 2014). It results from the multiple processes, which influence the gains and losses of thermal energy in streambeds, depending on the amount of stream discharge, topography and atmospheric conditions along the river course (Caissie, 2006).…”

Severity Multipliers as a Methodology to Explore Potential Effects of Climate Change on Stream Bioassessment Programs

“…Thus, it is important to understand these changes in relation to other anthropogenically driven changes for which biomonitoring metrics were designed to monitor. The results highlight the need for further testing of the vulnerability of bioassessment metrics to various aspects of global change and the potential for adopting metrics related specifically to climate change (e.g., [13,33,34]). …”

Did you say reference conditions? Ecological and socio-economic perspectives on the European Water Framework Directive

“…Climate change will not only change the ecological status of undisturbed areas, but will also interact with the impacts of human activities on biological communities (e.g., eutrophication and the coupling of thermal regimes and hydrology) and will exacerbate the uncertainties associated with the monitoring and assessment ((European communities, 2009). It is likely that the so-called reference biological communities are evolving and simulation exercises demonstrated the potential impact on the assessment of ecological status (Logez and Pont, 2013). Another major challenge to the concept of reference conditions stems from the observation that significant environmental modifications by humans have occurred for several millennia.…”