Water temperatures impact water chemistry and ecosystem productivity and biodiversity, thus water temperature is often regarded as a master environmental variable. Climate change is causing widespread river warming and a loss or fragmentation of cold-water habitat. Models project accelerated future river warming, which may catastrophically impact cold-water species biodiversity. For example, the Atlantic salmon is now classified as threatened or endangered in much of eastern Canada. Oceanographers have documented persistent oceanic warming as well as intensifying marine heat waves. These river and ocean temperature research endeavours have been conducted in segregated disciplines and have generally overlooked warming estuaries, which lie at the freshwater-marine interface.

Estuarine thermal regimes are complex, as they are governed by atmospheric conditions, estuarine hydraulics, and the temperatures of freshwater and marine inputs. Understanding estuarine thermal sensitivities is imperative because estuary temperatures control the migratory patterns and survival rates of anadromous fish. As estuaries warm, they may function as ‘thermal gates’ that impose migratory barriers. Also, Atlantic Canadian estuaries provide habitat for culturally and economically important cold-water shellfish, such as the blue mussel, which are often found in coastal bodies already experiencing high water temperatures.

The overall goal of the project is to develop an understanding of present and future estuarine thermal regimes through state-of-the-art thermal monitoring and modeling and to apply that knowledge to develop thermal management plans that enhance ecosystem resilience. The specific objectives are:

1. Expand the eastern Canadian water temperature network (www.rivtemp.ca) to include estuarine settings and augment time-series monitoring with loggers and new technology (drones and next-generation fibre optic distributed temperature sensing systems) to characterize temperature dynamics at unprecedented scales. Thermal monitoring will be combined with hydrologic/hydraulic and atmospheric monitoring.
2. Analyse the temperature, hydraulic, and climate data from the multiple sensors to quantify and classify thermal patterns in time and space for three study sites in order to characterise their thermal regimes and drivers;
3. Apply data from (2) to develop process-based numerical models of estuarine hydraulics and thermal dynamics under present-day conditions;
4. Compile downscaled climate scenarios to drive simulations of estuary warming to consider the interrelated impacts of atmospheric warming, ocean warming, and sea level rise on estuary temperatures and to reveal particularly vulnerable cold-water ecosystems;
5. Develop thermal and ecosystem management plans