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Aim: The regionalized patterns of biodiversity distributions are actively studied in terrestrial and marine ecosystems, but much less is known on the geographical patterns of ecoregions founded on freshwater taxa. Here, we studied, for the first time, how well existing freshwater ecoregions describe the geographical distribution of inland water plants. Location: Greenland, continental Canada and USA. Taxon: Freshwater vascular plants of all taxa and multiple functional groups (i.e. growth forms). Methods: Using newly available fine‐grained data on freshwater plant distributions, we studied how ecoregions founded on fish are suitable for freshwater plant regionalization across North America. Specifically, we calculated internal homogeneity and distinctness among neighbouring ecoregions in relation to species replacements and richness differences. We also explored how a complex suite of ecogeographical characteristics affect ecoregion delineation of freshwater plants using spatially explicit regression routines. Results: We found a clear geographical patterning of ecoregion robustness for North American freshwater plants, with communities being more internally homogeneous and more similar to one another in Polar and Subtropical inland waters. The degree of internal homogeneity and ecoregion distinctness were almost equally driven by species replacements and richness differences. Considering different life‐forms, ecoregion delineation performed best for emergent and floating‐leaved plants. Finally, within‐ecoregion homogeneity and distinctness were best explained by annual mean temperature and terrain ruggedness, respectively, with mean water alkalinity, ecoregion area and late Quaternary glacial legacies having supplementary effects. Main conclusions: Our findings suggest that selection through climate filtering (e.g. mean annual temperature) is likely the main mechanistic driver of freshwater plant ecoregions. Geographical regionalizations founded on a particular organismal group may not be directly applicable for all taxa but can be a good basis for further adjustments. Our study is a promising starting point for further investigations of geographical delineations for freshwater taxa other than fish. [ABSTRACT FROM AUTHOR]

The inland fisheries of North America (i.e. Canada and the United States of America) are diverse in terms of the sectors that harvest fish, the waters fished and the species targeted. Aboriginal fisheries have a long tradition of harvesting fish for food and ceremonial purposes using gears such as dip nets and spears, and targeting species such as suckers ( Catostomidae) and upriver migrating salmon ( Salmonidae). The commercial sector includes large-scale industrial operations on the Great Lakes and Mississippi River as well as smaller-scale fisheries throughout North America that harvest fish for food or the bait industry. The recreational fishery is the largest sector (millions of participants) and includes everything from specialised catch-and-release fisheries for muskellunge, Esox masquinongy Mitchill and black bass ( Micropterus spp.) to put-and-take fisheries for rainbow trout, Oncorhynchus mykiss ( Walbaum). All sectors provide substantial socio-economic benefit and regionally can have significant cultural value and yield an important amount of food protein. Using the best available information and a number of assumptions, total harvest for all three sectors in the inland waters of North America was estimated to be >480 000 t yr−1. Nonetheless, there are a number of internal threats that face these fisheries including over-exploitation, bycatch/release mortality as well as external threats such as inter-sectoral conflict, environmental change, water availability, invasive species and habitat alteration. Given that most inland fisheries are managed at the state/provincial level, there is a need to adopt management strategies that are holistic, coordinated and trans-jurisdictional if inland fisheries in North America are to be sustainable in the future. There is also a critical need for information management systems that enable regional data to be scaled up to the national or continental level, which would facilitate the generation of inland fisheries status reports and the monitoring of trends through time. All stakeholders must recognise that while inland fisheries tend to not receive the same attention from the media, public or politicians as marine fisheries, the potential for local and broad-scale irreversible changes exist and need to be identified and addressed if the many ecosystem services that inland fisheries provide are to be maintained. [ABSTRACT FROM AUTHOR]

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Widespread changes in water temperatures, salinity, alkalinity and pH have been documented in inland waters in North America, which influence ion exchange, weathering rates, chemical solubility and contaminant toxicity. Increasing major ion concentrations from pollution, human-accelerated weathering and saltwater intrusion contribute to multiple ecological stressors such as changing ionic strength and pH and mobilization of chemical mixtures resulting in the freshwater salinization syndrome (FSS). Here, we explore novel combinations of elements, which are transported together as chemical mixtures containing salts, nutrients and metals as a consequence of FSS. First, we show that base cation concentrations have increased in regions primarily in North America and Europe over 100 years. Second, we show interactions between specific conductance, pH, nitrate and metals using data from greater than 20 streams located in different regions of the USA. Finally, salinization experiments and routine monitoring demonstrate mobilization of chemical mixtures of cations, metals and nutrients in 10 streams draining the Washington, DC-Baltimore, MD metropolitan regions. Freshwater salinization mobilizes diverse chemical mixtures influencing drinking water quality, infrastructure corrosion, freshwater CO 2 concentrations and biodiversity. Most regulations currently target individual contaminants, but FSS requires managing mobilization of multiple chemical mixtures and interacting ecological stressors as consequences of freshwater salinization.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'., (© 2018 The Author(s).)