Harmful Algal Blooms: A Microscopic Problem! 


Absolutely! In normal quantities, algae are essential for ecosystems. When we talk about phytoplankton such as like toxin-producing dinoflagellates, 50% of the planet’s oxygen is attributable to them! Without their presence in our bodies of water, life on Earth as we know it would not exist.

Aquatic environments around the globe also depend on these single-celled organisms as the basis of their food chains. Without phytoplankton, zooplankton would have nothing to eat. All fish and marine mammal species that rely on them would therefore no longer be able to feed. A better understanding of what whales in the St. Lawrence eat allows us to implement more targeted conservation measures, though this is a complex process. In a recent article in Whales Online, we break it all down for you!

And besides, there aren’t many species that produce toxins! Only 2% of known phytoplankton species are thought to have the capacity to produce substances that are harmful to other animal and plant species.

Algal species that produce biotoxins like our Alexandrium catenella have complex life cycles that allow them to adapt to all kinds of conditions. After a growth phase in the form of a cyst, when water conditions are favourable, they begin their vegetative phase, which lasts the rest of their lives. They can thus migrate through the water column using their mobile filaments and take full advantage of the presence of nutrients in deep waters and light near the surface.

Blooms occur when one algal species monopolizes a large portion of the water column to the detriment of other species. The increased presence of toxins produced by some species can have fatal neurological impacts. In the event of particularly dense blooms, sunlight can no longer reach plants below the surface, which puts a stop to all productivity in the aquatic environment, even during the day. The environment is thus literally suffocated by cellular breathing.

Natural cycles of these blooms are observed in certain environments, but today we are seeing many more than before. The increased concentration of phosphate and nitrogen nutrients in our water bodies has been a particularly acute problem in recent years. These two nutrients are essential for the growth of all plants, and with the massive volumes entering the ecosystems through fertilizer runoff or domestic and municipal wastewater discharges, algae are having a field day! However, water temperature, oxygenation and acidity, precipitation, and even winds all have an impact on the presence and intensity of blooms.

Given the impact these algae can have on the quality of the environments in which they are found, it is essential to monitor their populations to know where and when blooms occur. Fisheries and Oceans Canada uses the Harmful Algae Monitoring Program (HAMP), which includes a sampling site near Tadoussac, and the Atlantic Zone Monitoring Program (AZMP) to count the various microalgae species in the St. Lawrence. Additionally, an interactive map developed by the St. Lawrence Global Observatory (SLGO) allows users to see the risk of Alexandrium catenella blooms throughout the river and estuary in real time.

Programs like this will become increasingly useful if the trend continues toward a steady increase in the presence of these problematic species in our waters.