This text is part of the special notebook Université du Québec à Rimouski
A research team from the University of Quebec at Rimouski (UQAR) is studying take a closer look at the repercussions of climate change on vegetated coastal ecosystems, composed for example of algae or underwater meadows.
Let’s start with the good news: the aquatic grass beds of the St. Lawrence River estuary are doing quite well. They are even expanding. Which is not to say that the river does not have its pollution problems. “This watercourse is so big that even if it is quite polluted around Montreal and Quebec, this pollution is diluted once it reaches the estuary, so the water quality remains adequate for the seagrass beds” , explains Fanny Noisette, professor of biological oceanography at the Rimouski Institute of Marine Sciences (ISMER).
It is important to take an interest in it, because underwater meadows have crucial functions in preserving the river’s ecosystem. In particular, they filter the nitrogen which comes from rivers, after having been dumped there mainly by agricultural companies. Excess nitrogen poses a great danger to a watercourse, as it can ultimately cause a lack of oxygen in the water, which will threaten all species.
As part of her master’s degree, student Marie-Pomme Poissant is, for example, seeking to find out more about these herbaria, whether in the laboratory by observing samples collected beforehand or in the field. “We calculate the quantities of carbon and oxygen that enter and leave the ecosystem and we also identify the macrofauna species [comme des larves d’insecte ou des mollusques] or invertebrates found there, to measure biodiversity and understand the role of each species,” she explains.
Improve our knowledge
Fanny Noisette’s team is also working to better document the seagrass beds of the coasts of the St. Lawrence estuary, James Bay and New Brunswick, which we do not yet know well. “We are trying to understand the factors which, in our northern climates, limit the growth of these environments, such as the quantity of available light,” explains Fanny Noisette.
Underwater plants grow through photosynthesis, like their terrestrial cousins. But in northern environments, they live under the ice for many months. “However, if pollution or turbulence increases the quantity of particles floating in the water, this prevents some of the sun’s rays from reaching plants and complicates their photosynthesis,” explains Marie-Pomme Poissant.
Fanny Noisette’s team also studies kelp forests, large brown algae commonly called sea lasagna. She first seeks to map them, then to identify factors that can harm them. The team has already observed that the Ice scraping in coastal areas releases a lot of this algae each year. “These detachments represent a large source of carbon export towards the open sea or towards the beaches,” underlines the professor.
This research has an interdisciplinary aspect. His team is also working on a project to link science and the arts. “Presenting a litany of figures is not the best way to mobilize citizens,” notes Marie-Pomme Poissant. By collaborating with artists, we can find ways to transmit new knowledge through their art. »
Assess groundwater quality
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