A translation by Judith Turcotte.
This song by Diane Dufresne (Donnez-moi de l’oxygène) comes to mind as I write this text. In my latest blogs, I described the consequences of the warming of the water in the Gulf of St. Lawrence: the lobsters are leaving the shores of the state of Maine for the gulf, the calamari are in abundance and the Nordic shrimp cannot be found. The warming of the water is not the only phenomenon that influences these important modifications to aquatic life. The oxygen levels in deep water are also an issue and it has been decreasing for a decade.
The St. Lawrence River suffers from deoxygenation, a phenomenon known under the name of hypoxia that affects the river’s deep water. There are two main causes of hypoxia in the gulf water. The first is the increase of phosphorus and the second, the increase of nitrogen both caused by agricultural fertilizer and wastewater discharges, two causes on which we can act.
We have a degree of ability to affect these causes of hypoxia; it is another thing for the warming of the water which also affects the oxygen level. The cold oxygen-rich water of the Labrador Current that comes to us from the Arctic and that flows into the Gulf is now replaced by the much warmer water of the Gulf Stream. The reasons for this major change are partly explained by climate change; however, the scientists are not convinced and continue to study other possible causes.
This decrease in oxygen affects the marine species that depend on oxygen to survive. Among the species affected, we find cod and halibut that cannot survive in these conditions. The Nordic shrimp must have gone back to live in shallower water; however, it was met by the redfish, one of its major predators.
These species have the advantage of being able to move while many other species are not mobile. There are dozens of species that live on the bottom of the gulf and that cannot easily move to zones richer in oxygen. The ones that come to mind are the shellfish including mussels, oysters and scallops. Lesser-known are the macroinvertebrates that include aquatic insects and worms.
The hypoxia, or low oxygen, is not the only trend affecting the marine biodiversity. The acidity of deep water is also rising sharply. These two phenomena add to the increase in water temperatures. In an article in the Devoir (May 22, 2024), the journalist, Alexandre Shields informs us that experts of Fisheries and Oceans Canada find it difficult to predict the impact of these upheavals. A consortium of researchers is conducting studies to better understand and anticipate the impact of these phenomena on the marine species of the St. Lawrence. It is good to understand, however, we must realize that we cannot do much faced with this new reality.