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

Temporal 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…

Publisher

Environment and Climate Change Canada

Resources

14

Catalogue metadata updated

2024-06-11