“We have almost record temperatures,” confirms the ministry’s physical oceanography researcher, Peter Galbraith. At depth, the waters are the warmest in the last three years. In the very thin cold intermediate layers, dissolved oxygen is at lower values and acidity is at a level almost never recorded. In our experience, the St. Lawrence has never been in such demand and in terms of pressure on resources.”
Record temperatures
A maximum average of 7 degrees Celsius was reached in 2022 in the deep waters of the Gulf. “At 6 degrees Celsius in 2015-2016, we were already at a record level,” underlines Mr. Galbraith. In 2023 there was a drop of one tenth compared to 2022, or 6.9 degrees Celsius. In the years to come, we are talking about a certain stability or a slight decline. But we still have a way to go to get below the first century-old record of 2015-2016. It’s going to take several years for that to happen.”
Surface waters are also getting warmer. A temperature higher than the anomaly by half a degree is already noticeable, according to the oceanographer. However, a temperature of 1.4 degrees Celsius, like what has been observed over the past three years, is certainly not normal.
His colleague Hugues Benoit indicates that this situation is not without causing significant changes, from which trends are emerging which are not encouraging. “At the same time, with warming, there are species that are doing very well,” says the scientific researcher. I think there are fishermen on the North Shore who are very happy because they are seeing species that they did not see before, like bluefin tuna.
Fisheries and Oceans Canada researchers presented a health report on the estuary and Gulf of St. Lawrence. In order: Diane Lavoie, Marjolaine Blais, Hugues Benoit and Peter Galbraith. (Johanne Fournier)
Acceleration
In Peter Galbraith’s opinion, the closer we get to the surface, the more there are temperature fluctuations depending on the year. In the long term, the specialist notes that temperature warming accelerates twice as quickly in winter as in summer, but with much more variation. “The further down we go in the water column, the interannual variations are slower and there are fewer of them. But, in all layers, there is a warming trend.”
According to aquatic sciences biologist Marjolaine Blais, hypoxia is also increasing because the waters of the Gulf Stream, which are poorer, are taking up more and more space, although a certain stabilization has been observed in recent years. last year. In addition, the acidity levels of surface waters are decreasing twice as fast as the global ocean average, observes her colleague specializing in the acidification of the St. Lawrence, Martine Lizotte. In deep water, it’s three times faster.
Loss or increase of biodiversity?
Diane Lavoie is participating in studies aimed at knowing whether or not habitats will be favorable to different species by 2080.
“For lobster, increasing temperatures are favorable, but due to acidification, there will be unfavorable conditions at some point,” warns the researcher. Will this be compensated by better temperature conditions? There are a lot of questions to answer.”
— Diane Lavoie
Furthermore, will an increase in temperature cause a loss of biodiversity in the estuary and Gulf of St. Lawrence? “This is a question to which we do not have a precise answer at the moment,” says researcher Marie-Julie Roux. However, with the presence of warm and cold waters, researchers are currently witnessing the arrival of new arrivals. “Cold water species are in an environment that is increasingly unfavorable to them, while warm water species are in an environment that favors them. This can, in the long term, lead to an increase in biodiversity.”
In addition, the species which enter the gulf had already been seen by scientists, specifies Hugues Benoit. So silver hake and squid appear to be making a comeback in the Gulf. On the other hand, the distribution area of the northern shrimp is restricted. “It should still succeed in finding refuge at temperatures to which it is more adapted, with dissolved oxygen levels which are also more favorable to them,” the researcher nevertheless predicts. But we do not foresee, in the short term, the complete disappearance of shrimp in the Gulf.
For its part, herring responds to thermal preferences by reducing its size, notes Mr. Benoit. Although strong declines of this species have been noted in the warmest ecosystems, they are much less pronounced in the north. In terms of population productivity and fishing yield, the observed and anticipated consequences boil down to smaller adults, fewer in number and possibly producing fewer juveniles, he says.
Equipment
Fisheries and Oceans scientists use smart buoys which are deployed at around ten stations in the St. Lawrence. “These are buoys that provide real-time data,” explains Peter Galbraith. They are equipped with a temperature profiler. They can measure not only what’s happening on the surface, but also in the water column.”
The buoys also allow them to observe the effect of post-tropical storms. “We saw buoys that survived waves of 13 to 15 meters in height like we saw during storms Dorian And Fiona», underlines the oceanographer.
Although researchers can count on new technologies, the assessment of the state of the St. Lawrence cannot be done without traditional methods, namely the collection of water samples on board ships. Furthermore, Peter Galbraith indicates that he and his team have, for 29 years, been the only ones in the world to carry out large-scale sampling from a helicopter.
