Aquatic pollutant assessment across multiple scales

Aquatic pollutant testing using biological assays is useful for ranking the toxicity ofdifferent chemicals and other stressors, for determining acceptable concentrations inreceiving systems and for elucidating cause and effect relationships in the environment.This \u27ecotoxicological\u27 testing approach supplants previous approaches that indirectlyestimated toxicity using chemical and physical surrogate measurements alone. Nevertheless, many published aquatic pollution studies are restricted to examining theeffects of a single toxicant on only a single species. Moreover, laboratory-basedecotoxicity tests often intrinsically suffer from a number of limitations due to their smallscale.For example, a major criticism of single-species bioassays is their failure tointegrate and link toxicants (and other associated abiotic components) with higher scalesof biological and ecological complexity (predation, competition, etc.). Many researchershave suggested that single-species toxicant testing has become so widely entrenched thatit has hindered the development and greater use of testing at more ecologically-relevantscales. An improvement to single-species laboratory tests are microcosm and mesocosmstudies using more complex and relevant measures to aquatic biotic communities.Nevertheless, mesocosms still do not entirely simulate the ecosystem they come from,rather they mirror its general properties. As a result, there is increasing interest incorrelating pollution measures from field surveys with measures of aquatic bioticcommunity structure to determine a toxicant\u27s scale of effect. However, fieldassessments, although extremely useful in determining site-specific impacts, may belimited by lack of experimental controls, too few or poorly-positioned regional referencesites and by confounding effects from impacts unrelated to the disturbance of concern. A hegemony on the evolution of ecotoxicological science and practice is that theprimary application of ecotoxicological data is regulatory. As ecological systems do nothave a single characteristic of scale, validation of single-species toxicity assessmentsby higher ecological level assessments remains the highest standard for aquatic pollutionstudies. As such, multi-scale assessments at all of these scales are now being recognisedas providing the highest reliability for environmental protection of lake ecosystems