Spatial scale affects community concordance among fishes, benthic macroinvertebrates, and bryophytes in streams.

Owing to the lack of information about the distribution patterns of many taxonomic groups, biodiversity conservation strategies commonly rely on a surrogate taxa approach for identifying areas of maximum conservation potential. Macroinvertebrates or fish are the most likely candidates for such a role in many freshwater systems. The usefulness of the surrogate taxa depends largely on community concordance, i.e., the degree of similarity in community patterns among taxonomic groups across a set of sites. We examined the effect of the spatial scale of a. study on the strength of community concordance among macroinvertebrates, bryophytes, and fish by comparing the concordance between ordinations of these groups in 101 boreal stream sites. We specifically asked if communities spanning several drainages are more concordant than those originating from a single drainage system. Our results indicate that community concordance is affected by spatial extent, being variable and generally weak at the scale of individual drainages, but strong across multiple drainage systems and ecoregions. We attribute this finding to different taxonomic groups responding to similar environmental factors and sharing a similar latitudinal gradient of community structure when viewed across large spatial scales. We also identified a "gradient of concordance," with sites contributing disproportionately to community concordance being in relatively large streams with high microhabitat variability. Overall, our results suggest that the degree of community concordance among freshwater organism groups depends critically on the spatial extent of the study, and surrogate groups at the scale of single river systems should be used with caution.     

Factors affecting the severity of injuries among young motorcyclists--a Swedish nationwide cohort study

OBJECTIVES: To determine factors affecting the severity of motorcycle injuries, considering variables related to the individual, the environment, the vehicle, and the crash. METHODS: This is a register-based retrospective cohort study. All individuals born in 1970-1972 (n = 334,070) were extracted from the Swedish Population and Housing Census of 1985 and followed up from 1988 to 2000, when aged 16-30. All subjects whose records indicated an injury as a motorcycle driver in the Swedish National Road Administration Accident Database were selected, and constituted the study population (n = 1,748). Factors related to the individual, the environment, the vehicle, and the crash were considered as exposure measures, whereas the outcome measure was the level of injury severity, based on assessments made on-site by police officers, in two categories: fatal/severe and minor. Associations between individual, environmental, vehicle and crash factors and injury severity were measured, using Chi-square, and through univariate and multivariate stepwise logistic regression. RESULTS: Factors such as alcohol consumption, traffic environment, speed limit, and type of crash were significantly associated (p < 0.0001) with injury severity. More specifically, a positive suspicion of alcohol consumption, driving in a rural area, and a posted speed limit over 50 km/hour were all factors positively associated (OR > 1.0) with the likelihood of being severely injured. On modeling all the variables together through stepwise logistic regression, positive suspicion of alcohol emerged as the strongest determinant (adjusted OR = 2.7) of a severe outcome. CONCLUSIONS. Motorcycle crashes still place a heavy burden on young drivers. Increased efforts are needed to prevent alcohol-related crashes-through law enforcement and a multiplicity of policies at local and national levels.     

The impact of atrazine on lake periphyton communities, including carbon uptake dynamics using track autoradiography

Chlorophyll a, freshweight biomass, ash-free dry weight, cell numbers, species richness, community carbon uptake and species-specific carbon uptake were used to monitor the impact of atrazine (2 chloro-4-ethylamino-6-isopropylamino-s-triazine) on an in situ, enclosed periphyton community. Atrazine concentrations ranging from 0.08 to 1.56 mg litre(-1) were used during the 2 years of study. In both 1982 and 1983, there was a shift from a chlorophyte- to a diatom-dominated community. In 1982 the cyanobacterium Cylindrospermum stagnale and the chlorophyte Tetraspora cylindrica developed isolated colonies in the 1.56 mg litre(-1) treatment, indicating resistance to atrazine at this concentration. After atrazine exposure, community productivity was reduced by 21% to 82% in the low to high exposures, respectively. After day 21 productivity returned to control levels. It was shown, using track autoradiography, that the productivities of the larger algae Mougeotia sp., Oedogonium sp., Tolypothrix limbata and Epithemia turgida were the most affected, with reductions of 74.3% to 93.1% that of the controls. All the biotic measures indicated reduced growth after herbicide exposure.     

Nitrate and nitrite injection during municipal solid waste anaerobic biodegradation

Nitrified leachate recirculation has been proposed as a promising strategy for sustainable landfill management. In four test reactors, nitrate or nitrite was added (250 mg N-NO(x)(-)L(-1)) during municipal solid waste biodegradation. Nitrogen-oxides reduction reactions were monitored. Denitrification was the main nitrogen reducing reaction observed. On one hand, during the acidogenic waste degradation phase, as high amounts of volatile fatty acids (VFA) were present, nitrogen-oxides reductions were interpreted as heterotrophic denitrifications. On the other hand, denitrification reactions occurring during the late methanogenic phase were accompanied by sulphate productions and, as VFA were not detected, it was probably an autotrophic reaction. Denitrification inhibition was observed once. Ammonium concentration increased suggesting the occurrence of a dissimilatory nitrate reduction to ammonium (DNRA). Statistical treatment of analytical data revealed that only H(2)S concentration had a significant negative effect on N(2) production in our system. NO production was observed once when nitrite was injected during the acidogenic phase resulting in a total waste degradation inhibition. These results indicate that the consequences of nitrified leachate recirculation in full-scale landfills need to be carefully examined especially during the acidogenic phase or in the presence of waste containing high quantities of sulphur.     

Microplastic contamination in Great Lakes fish

Freshwater ecosystems, generally adjacent to human population and more contaminated relative to adjacent marine ecosystems, are vulnerable to microplastic contamination. We sampled 7 species of fish from Lake Ontario and Lake Superior and assessed their gastrointestinal (GI) tracts to quantify ingested microplastics and other anthropogenic particles. A subset of the microparticles were chemically analyzed to confirm polymer types and anthropogenic origins. We documented the highest concentration of microplastics and other anthropogenic microparticles ever reported in bony fish. We found 12,442 anthropogenic microparticles across 212 fish (8 species) from nearshore Lake Ontario, 943 across 50 fish (1 species) from Humber River, and 3094 across 119 fish (7 species) from Lake Superior. Fish from Lake Ontario had the greatest mean abundance of anthropogenic microparticles in their GI tracts (59 particles/fish [SD 104]), with up to 915 microparticles in a single fish. Fish from Lake Superior contained a mean [SD] of 26 [74] particles/fish, and fish from Humber River contained 19 [14] particles/fish. Most particles were microfibers. Overall, ≥90% of particles were anthropogenic, of which 35-59% were microplastics. Polyethylene (24%), polyethylene terephthalate (20%), and polypropylene (18%) were the most common microplastics. Ingestion of anthropogenic particles was significantly different among species within Lake Ontario (p < 0.05), and the abundance of anthropogenic particles increased as fish length increased in Lake Ontario (ρ = 0.62). Although we cannot extrapolate the concentration of microplastics in the water and sediments of these fish, the relatively high abundance of microplastics in the GI tracts of fish suggests environmental exposure may be above threshold concentrations for risk.     

Effects of anthropogenic landscapes on population maintenance of waterbirds

Anthropogenic impacts have reduced natural areas but increased the area of anthropogenic landscapes. There is debate about whether anthropogenic landscapes (e.g., farmlands, orchards, and fish ponds) provide alternatives to natural habitat and under what circumstances. We considered whether anthropogenic landscapes can mitigate population declines for waterbirds. We collected data on population trends and biological traits of 1203 populations of 579 species across the planet. Using Bayesian generalized linear mixed models, we tested whether the ability of a species to use an anthropogenic landscape can predict population trends of waterbird globally and of species of conservation concern. Anthropogenic landscapes benefited population maintenance of common but not less-common species. Conversely, the use of anthropogenic landscapes was associated with population declines for threatened species. Our findings delineate some limitations to the ability of anthropogenic landscapes to mitigate population declines, suggesting that the maintenance of global waterbird populations depends on protecting remaining natural areas and improving the habitat quality in anthropogenic landscapes. Article impact statement: Protecting natural areas and improving the quality of anthropogenic landscapes as habitat are both needed to achieve effective conservation.