The St. Lawrence River, Canada-USA: the Need for an Ecosystem-Level Understanding of Large Rivers.

Abstract

Although large rivers are important wildlife habitats and a valuable resource for potable water, transport, energy generation and waste disposal, they have received relatively little attention by limnologists. Successful management of these environments will require consideration of their unique properties as living systems. Using examples from the St. Lawrence River, we identify environmental pressures on large rivers that would greatly benefit from an integrated `whole ecosystem' approach towards their understanding and management: hydraulic control, channel modification, contaminant discharge (industrial carrying capacity), eutrophication, climate change and community shifts, including the invasion of exotic species. The downstream reach of such environments, in particular the freshwater-saltwater transition zone (FSTZ), is a critical ecotone for the entire river system and is highly sensitive to each of these anthropogenic effects. The FSTZ integrates upstream and downstream processes, is one of the most biologically productive sections of the river, and is a prime site for monitoring fluvial and estuarine health.