Temporal changes in human pressures and wetland response in the St. Lawrence River

Temporal changes in human pressures and wetland response in the St. Lawrence RiverTemporal changes (1970–2016) in St. Lawrence River wetlands were assessed between Cornwall and Québec to assess wetland response to cumulative anthropogenic pressures in the watershed. Emergent wetlands area and biomass of submerged aquatic vegetation (SAV) were contrasted among five regions subjected to sharply different water level\/discharge regime (stabilized, semi-natural, tidal), nutrient concentrations and shoreline use (rural to urbanized). Between 1970 and 2016, over the growing season, St. Lawrence River mean water level have dropped and mean water temperature increased. Reductions in phosphorus concentrations were observed over time both in water and in SAV tissues, in phase with improvements of urban wastewater treatment and phosphorus reduction in upstream Lake Ontario. Nitrate concentrations in water increased and SAV biomass decreased between the 1970s and 2008 in the downstream regions of Lake Saint-Pierre and fluvial corridor subjected to the cumulative impacts from urban centers and intensively farmed watersheds. Over the 1970–2010 period, dropping water levels yielded slightly increasing wetland areas, owing to the downslope colonization of emergent and submerged plants. In urbanized regions, emergent wetlands shifted towards drier assemblages dominated by invasive reed species. Encroachment of wetlands by agriculture accounted for most wetland losses in rural Lake Saint-Pierre, which holds the single largest area of continuous wetland habitat of the entire watershed. The results highlight the strong response of riverine wetlands to a wide range of human pressures, including dropping water levels, changing nutrient concentrations, rising population and intensifying agriculture.


External resources

Link Name Protocol
Scientific Publication - Temporal (1970\u20132016) changes in human pressures and wetland response in the St. Lawrence River (Québec, Canada)
Scientific Publication - Spatial Analysis of Production by Macrophytes, Phytoplankton and Epiphyton in a Large River System under Different Water-Level Conditions
Scientific Publication - Physical variables driving epiphytic algal biomass in a dense macrophyte bed of the St. Lawrence River (Quebec, Canada)
Scientific Publication - Shift in wetland plant composition and biomass following low-level episodes in the St. Lawrence River: looking into the future


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