Multiscale drivers of phytoplankton communities in north-temperate lakes.

Multiple factors operating across different spatial and temporal scales affect ß-diversity, the variation in community composition among sites. Disentangling the relative influence of co-occurring ecological drivers over broad biogeographic gradients and time is critical to developing mechanistic understanding of community responses to natural environmental heterogeneity as well as predicting the effects of anthropogenic change. We partitioned taxonomic ß-diversity in phytoplankton communities across 75 north-temperate lakes and reservoirs in Alberta, Canada, using data-driven, spatially constrained null models to differentiate between spatially structured, spatially independent, and spuriously correlated associations with a suite of biologically relevant environmental variables. Phytoplankton ß-diversity was largely independent of space, indicating spatial processes (e.g., dispersal limitation) likely play a minor role in structuring communities at the regional scale. Our analysis also identified seasonal differences in the importance of environmental factors, suggesting a general shift toward greater relevance of local, in-lake (e.g., nutrients and Secchi depth) over regional, atmospheric and catchment-level (e.g., monthly solar radiation and grassland coverage) drivers as the open-water growing season progressed. Several local and regional variables explained taxonomic variation jointly, reflecting climatic and land-use linkages (e.g., air temperature and water column stability or pastureland and nutrient enrichment) that underscore the importance of understanding how phytoplankton communities integrate, and may serve as sentinels of, broader anthropogenic changes. We also discovered similar community composition in natural and constructed water bodies, demonstrating rapid filtering of regional species to match local environmental conditions in reservoirs comparable to those in natural habitats. Finally, certain factors related to human footprint (e.g., cropland development) explained the composition of bloom-forming and/or toxic cyanobacteria more than the overall phytoplankton community, suggesting their heightened importance to integrated watershed management.

Prevalence, levels and seasonal variations of human enteric viruses in six major rivers in Alberta, Canada.

The prevalence and seasonal variation of 7 viruses in 6 major rivers in Alberta were assessed using a combination of qPCR, cell culture and integrated cell culture with qPCR (ICC-qPCR). Water samples were collected monthly from rivers at different sites upstream and downstream of major urban centers. Seven viruses including rotavirus, adenovirus, astrovirus, norovirus, sapovirus, JC virus and enterovirus, were detected in at least one of the water samples at each site using qPCR. Rotavirus was most common with concentration ranging from 2.3 to 4.5 log10 genomic equivalent (GE) copies/L. Norovirus, sapovirus, astrovirus, adenoviruses and JC virus peaked during the winter (November to March). Viruses were most prevalent at the Bow River sampling site downstream of the City of Calgary, followed by the North Saskatchewan River site downstream of the City of Edmonton and the Red Deer River site downstream of the City of Red Deer. The detection rates and quantity of viruses had significant difference in the sampling sites between upstream and downstream of major urban centers (p < 0.001). 14% of the samples tested positive using viral culture indicating the presence of infectious viruses in river. Sequencing analysis identified human rotavirus in 75% of the samples collected from downstream versus 37% of the samples collected from upstream sites (p < 0.02). Multivariate binary regression showed that human activity in watersheds is a significant determinant of viruses in Alberta's Rivers. The discharge from wastewater treatment plants may be the possible sources of viral contamination. Seasonal coincidence of acute viral gastroenteritis outbreaks and monthly peak occurrence of enteric viruses in river water implies potential impact of waterborne viruses on human health.