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Published: 2021-01-20

Nutrients affect Arctic freshwater responses to global warming

NEWS Arctic freshwaters have naturally low concentrations of nutrients, and the current trend points toward decreasing levels, possibly driven by climate warming. Maria Myrstener shows that this has the potential to decrease primary productivity of these ecosystems. Maria defends her thesis on Friday 22 January at Umeå University.

Text: Ingrid Söderbergh

Primary productivity, which is growth of algae and plants, in Arctic waters support unique food webs, regulate water quality, and affect carbon dioxide emissions. Yet, we know very little about which physical and chemical parameters control this productivity, especially outside the normal growing season.

In her thesis, Maria Myrstener has focused on developing knowledge on how these ecosystems function today, to predict in a better way how they are being affected by current climate change. The studies have foremost taken place in Arctic mountain streams in and around Abisko in Norrbotten County.

The low availability of essential nutrients such as nitrogen and phosphorus in Arctic streams showed to have large effects on how these ecosystems function, including the seasonality of aquatic primary production. When nutrient concentrations drop during summer, this limits the growth of algae, and carbon dioxide uptake decreases.

During spring and autumn on the other hand, when nutrient concentrations are higher, the potential for algal growth increases. Maria shows that despite extremely low temperatures, some of her study streams peak in primary productivity during these ‘shoulder’ months in spring and autumn. As result the patterns in aquatic primary production can be strongly off set from terrestrial growing season patterns, which peak during mid-summer.

The strong nutrient limitation the researchers see in these waters effect essentially all parts of the ecosystem functions that Maria Myrstener has studied, including carbon dioxide uptake, algal biomass, seasonal patterns, and the capacity for stream nutrient uptake.

“With a continued rapid rise in temperature and declining nutrient concentrations, we unfortunately expect that these mountain streams will be negatively affected,” says Maria Myrstener.

Read the whole thesis

Press photos. Credit: Maria Myrstener


About the dissertation:

On Friday 22 January Maria Myrstener, Department of Ecology and Environmental Sciences at Umeå university, defends her thesis entitled: The role of nutrients for stream ecosystem function in Arctic landscapes: Drivers of productivity under environmental change.

The dissertation takes place at 9:00 in room KB.G5.01, KBC building at Umeå University and via Zoom.

Faculty opponent is professor Tenna Riis, Department of Biology, Aquatic Biology, Aarhus Universitet. Supervisor is Ryan Sponseller