Water Quality in the Fluvial Corridor and the Estuarine Transition Zone of the St. Lawrence River - Lampsilis Annual Missions (MAL)

Every summer since 2017, scientists involved in the annual Lampsilis missions have sampled and measured physico-chemical and biological water parameters related to the health of the St. Lawrence River. The data collected during these missions (funded since 2019 by the different programs of the [Réseau Québec maritime](https://www.rqm.quebec/)) have contributed to the effort of long-term monitoring, aimed at increasing our understanding of the functioning of this ecosystem. Due to the sampling challenges associated with large and complex ecosystems, this ongoing dataset is unique and has rarely been found for large river systems. The reactivity of first trophic levels in large river system food webs associated with changes in water masses and land uses is still largely unknown. Variables such as dissolved organic matter and chlorophyll, and changes in the structure and functioning of bacterial communities could provide useful information on the evolution of the river and its tributaries. However, only a few studies have measured these variables in an entire river system. In order to push forward remediation efforts in terms of water quality, it is necessary to understand the functioning of the St. Lawrence River and the transformation processes naturally in place in the system.

The two main objectives of the scientific missions were to assess changes in organic matter (dissolved organic carbon, nitrogen and phosphorus), and the structure and functioning of the bacterial community within the St. Lawrence River. More specifically, these variables were used to determine the source of contamination entering the river, and to observe longitudinal and lateral spatial variations in physico-chemical and biological parameters of water over the entire fluvial section of the St. Lawrence River. These objectives have been supported by 5 years of summer sampling aboard the Lampsilis, with the underlying mandate to create a complete data set that includes both temporal and spatial variability.

The data provided here are physico-chemical parameters of water masses, including temperature, conductivity, pH, turbidity, and the concentrations of dissolved oxygen, chlorophyll-a, total nitrogen and total phosphorus.

## List of the associated research projects
- Exploring the dynamics of water quality from Lake Ontario to the St. Lawrence Estuary (François Guillemette – UQTR)
- Tracing the changes in bacterial metabolism in response to natural and anthropogenic inputs to the St. Lawrence River (François Guillemette – UQTR)