The rise in temperature has many repercussions on the climate, according to Al-Mahdi Bendev, a professor specializing in phytoplankton physiology at the Rimouski Institute of Marine Sciences. “We see melting ice, rising water levels, ocean acidification, and an increase in storm surge [en nombre et en intensité] or extreme weather events such as droughts, landslides, or floods. »
Another equally important but more discreet consequence: a decline in phytoplankton. Above a certain temperature, around 20 degrees Celsius, this single-celled organism (cyanobacteria and microalgae) enters a state of stress. Then some part recovers, but its ability to photosynthesize is reduced.
in the past few years, Decrease in phytoplankton production It was discovered by scientists at the Massachusetts Institute of Technology (MIT). In the North Atlantic, their population has declined by 10% since the beginning of the industrial age. The decline in phytoplankton is unfortunately synonymous with ocean depletion, as it is at the base of the food chain. In addition, this phenomenon reduces the ability of seas to store atmospheric carbon; Phytoplankton convert carbon dioxide2 organic matter during photosynthesis. It is estimated that they absorb more than a quarter of all carbon dioxide emissions2.
migration and acidification
In addition, a warming ocean is causing phytoplankton to migrate, according to the prof. “Species that live in the tropics will move towards the poles. Those that already live in the cold have a harder time adapting and will shrink more.” [vers les régions plus froides]. The consequences can be dire for the population [marines] already well established. »
Phytoplankton also suffer from acidification of the water. In a study, Professor Bendev showed that it causes erosion of limestone scales of certain phytoplankton, which then release carbon dioxide.2 that contain.
The consequences then appear for the oceans: a natural decline in the number of marine and terrestrial populations, a decrease in oxygen production and an increase in carbon in the air and thus in climate change.
In recent years, scientists and companies have proposed fertilizing the oceans with iron or nitrogen to stimulate the growth of phytoplankton. “According to all models, it is not viable in the long term,” analyzes Mehdi Bendev. This must be accompanied by a significant change in our carbon dioxide emissions2. The real problem is human activity and our way of consuming. solutions at this level. »
