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There is a need to develop bioassessment tools that can diagnose the effects of individual stressors that can have multiple ecological effects. Using nuclear magnetic resonance (NMR)-based metabolomics, our experiments aimed to identify the sensitivity of metabolites to changes in food availability and dissolved oxygen (DO) concentrations, and compare these results to identify metabolites that may differentiate between the effects of these two stressors. Forty-eight, laboratory-raised, red swamp crayfish (Procambarus clarkii) were randomly assigned and exposed to one of three food availability or DO treatment levels (high, normal, low). Starved crayfish had lower amounts of amino acids than fed crayfish, suggesting catabolic effects of starvation on tail muscle tissue for energy requirements. In contrast, crayfish exposed to hypoxic conditions experienced changes in abundance of metabolites primarily associated with energy metabolism. Tail muscle was the only tissue sensitive to food and DO stress, suggesting the need to select tissues for monitoring appropriately. Our evaluation of environmental metabolomics as a tool for bioassessment indicates that several identified metabolites in crayfish tail muscle may be able to diagnose food and oxygen stress. Further study is required to determine if these metabolic effects are linked with changes of individual fitness and higher levels of biological organization, such as population size. [ABSTRACT FROM AUTHOR]

Stressor (or human activity) gradients that quantify variation in the magnitude and type of human activity among sites are an important and widely applicable tool for aquatic monitoring and assessment. These gradients are typically determined from regional land cover data. We predicted that their performance could be improved by incorporating less generalized depictions of human activities. Using data from 479 rural, headwater basins we calculated four human activity gradients (HAGs) that differed in the level of detail (coarse, fine) and spatial explicitness (aspatial, spatial) used to describe human activity. Results demonstrated that the addition of fine detailed information was valuable as it resulted in aHAGthat captured subtle differences in the extent of human activity among study units. In comparison, the addition of spatially explicit data added little novel information to theHAG.Analysis of fish and benthicmacroinvertebrate samples from 160 of the 479 basins indicated that the addition of fine detailed and spatially explicit information significantly increased the ability of the HAG to predict variation in aquatic assemblages. We concluded that HAGs can better meet the requirements of monitoring and assessment programs if detailed and spatially explicit descriptions of human activity are used along with more typically available land cover data. [ABSTRACT FROM AUTHOR]

Bioassessment is based upon the premise that biological assemblages have predictable relationships with the surrounding natural and human environments. As the nature of these relationships can vary from region to region, it is important that environment–biota relationships be established prior to the initiation of any bioassessment program. In this study, multivariate analysis was used to establish how fish and benthic macroinvertebrate (BMI) assemblages in southwestern Ontario streams vary across natural and human activity gradients. The use of canonical correspondence analysis allowed us to determine that changes in community composition of both fish and BMI are strongly correlated with variation in the extent of human activity. The primary source of variation in community composition across activity gradients appeared to reflect a shift from intolerant to tolerant taxa as the extent of human activity increased. Habitat and feeding traits, for BMI and fish respectively, accounted for a secondary source of variation primarily attributable to differences in the extent of human activity at the reach scale. However, variation in human activity, especially at the basin scale, covaried with the dominant natural gradient of surface geology, making interpretation of the results difficult. Implications for bioassessment studies are discussed. [ABSTRACT FROM AUTHOR]