Quebec’s territory is covered by millions of lakes and those located in densely populated areas in the south are subjected to the influence of human activities in their catchments. An increasing number of these lakes are affected by eutrophication, showing recurring blooms of cyanobacteria (blue-green algae). Since the summer of 1999, cyanobacterial blooms were reported from more than 200 water bodies throughout southernmost Quebec. In 2002, almost 40 lakes were affected by restrictions of access and use associated with these blooms, and by the end of 2007 more than 225 lakes were concerned (Ministère du Développement Durable, de l’Environnement et des Parcs, 2008).
The appearance of cyanobacterial blooms is neither a phenomenon specific to the freshwater ecosystems of Quebec, nor a new environmental problem. Several countries are dealing with the challenges and problems associated with the massive and fast proliferation of cyanobacteria. The extent of proliferations reported from Quebec during the past two years raised many concerns, which were widely diffused through the media and discussed at national (conference Institut Hydro-Quebec EDS, January 2008) and international congresses and symposia (e.g. SIL August 2007). The discussions revealed not only an urgent need for a better understanding of the problem, its origins and consequences, but also the importance of an improved knowledge for better decision-making and management.
Paleolimnology is the science that studies the historical perspective of freshwater ecosystems, and its scientific approach provides the necessary background or baseline information for detecting causal mechanisms, and thus sound decision-making. Within this innovative research project, for each study lake detailed information is generated that is related to:
• the extent of the trophic changes that occurred in the lake over the past ca. 200 years;
• the evolution and succession of changes in the composition of cyanobacterial communities during the past 200 years;
• the determination of critical phosphorus levels and thresholds that correspond with the appearance of undesirable symptoms, and
• the cause and effect relationships between human activities in the lake catchment and perturbations in the lake.
Following these research objectives, we intend to develop predictive models using bioindicators (diatoms and pigments) for documenting the influence of certain physical and chemical processes and components on the evolution of water quality in Quebec lakes. These models will be useful as tools for the reconstruction of certain key environmental variables (e.g., phosphorus) from long sediment core sections, as well as for the development of diatom indexes for the follow-up (monitoring) of the lake’s trophic state. Moreover, this work represents the first attempt towards the development of a predictive model for cyanobacterial blooms using their own fossil bioindicators (pigments).