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The ice cover on the St. Lawrence is particularly weak this year, the scientists note. Global warming should accentuate the phenomenon in the coming years, which risks aggravating coastal erosion and representing an additional threat for certain species, including the St. Lawrence beluga.
Head of the Ecosystem Dynamics Section at Fisheries and Oceans Canada, Peter Galbraith, is familiar with the ice cycle that forms in winter on the waters of the Estuary and Gulf of St. Lawrence. But this year, by observing the maps which make it possible to follow the evolution of the situation on a daily basis, he notes above all the absence of this white cover which is normally very present.
“We are close to the historic minimums for the date,” he underlines, in an interview with the Duty. Typically, by mid-February, there would be more than 40 km3 of ice over the whole of this vast maritime region, which means that the cover would extend well beyond the limit of the estuary to cover the waters of the gulf, up to encircle the Magdalen Islands.
This winter, however, we are far from the mark since in mid-February, there were between seven and nine cubic kilometers of ice. “There is very thin ice in some areas around Prince Edward Island and in Chaleur Bay, but overall you can hardly see any ice,” Galbraith said. And there is virtually no chance that the frozen cover will catch up to reach the maximum ice expansion, which can normally reach more than 60 km3 at the beginning of March.
“As a rule of thumb, nearly half the volume of the Gulf must be cooled to near freezing to form ice. But this year, the temperature is well above the freezing point. There shouldn’t be much ice cover this year. If the trend continues, we could see the sixth ice-free year in the recent history of the Gulf of St. Lawrence,” explains Peter Galbraith.
Warming
Global warming, which increasingly tends to warm the air above the waters, despite interannual variability, is obviously singled out. This therefore portends the worst for the next few years. “If we project ourselves with the current trend, we are about to pass the milestone where winters with ice cover should be the exception rather than the rule”, warns the researcher.
The same goes for Émilien Pelletier, Professor Emeritus in Molecular Ecotoxicology in Coastal Environments at the Rimouski Institute of Marine Sciences. The latter said he observed exceptionally ice-free waters in front of Rimouski. “The reduction in ice cover has been a strong trend over the past 10 to 15 years and overall, as there is less ice, the waters will warm up earlier in the spring,” he argues.
This warming should rhyme with the early start of “primary production”, which corresponds in particular to the blooms of microscopic algae, phytoplankton, a food resource at the base of the food chain of this marine ecosystem. There is therefore a risk that this production will not be in phase with the species that depend on it. But for the moment, this issue and its potential impacts must still be studied to be better understood.
Belugas at risk
What we do know, however, is that the reduction in ice cover could add an additional threat to the survival of St. Lawrence belugas. The vast majority of this population of approximately 880 individuals moves east and the Gulf of St. Lawrence in winter. Animals have already been observed in the Sept-Îles and Port-Cartier sectors, but also along the Gaspé Peninsula and around Anticosti Island.
Belugas look for areas that are largely covered in ice. This could allow them to shelter from storms and strong winter waves, which can cause large energy expenditure. “In all beluga populations, there is a strong association between the winter distribution of belugas and the ice edge. The function is not clear and may not be the same for all populations”, recalls Robert Michaud, president and scientific director of the Group for Research and Education on Marine Mammals.
As part of the work on the increase in mortalities of females about to give birth, or who had just given birth, the researchers however noted a “coincidence” with the reduction in the ice cover, he adds.
“A reasonable, but difficult to validate, hypothesis suggests that the decrease in ice cover could force females to make greater movements in winter and reduce their protection against rougher seas. This could result in higher energy costs to pregnant females,” says Michaud. You should know that in March, they are three or four months away from giving birth, after a gestation period of 14 months.
By combining this phenomenon with other suspected and demonstrated impacts of human activities (decline in fish stock, noise and reduction in feeding efficiency, disturbance), “this increase in energy expenditure may have had an effect on the physical condition of females and their reproductive success”, continues the man who has been studying the species for nearly 40 years.