Natural and societal consequences of climate-forced changes of Jostedalsbreen Ice Cap
Why is there Elevated Nitrate in Glacially-fed Lakes?
by Miranda Herschel Seixas, October 2, 2025
In early August, researchers from the University of Maine, USA, in collaboration with HVL and JOSTICE, sampled three glacially-fed lakes on the edge of Jostedalsbreen – Brevatnet, Nigardsbrevatnet, and Styggevatnet. These turquoise lakes are directly fed from glacial melt streams and as the rate of glacial retreat increases, lake size and characteristics are also changing (see “Recent retreat of Nigardsbreen alters local weather and climate” for some more specifics on these changes). Glacially-fed lakes differ greatly from neighboring precipitation-fed lakes. Generally, glacially-fed lakes are cold and abundant in glacial flour, which inhibits light penetration, thus creating a dark environment. Much like glacially-fed lakes around the world, these lakes have high concentrations of nitrate, a very bioavailable form of nitrogen. The source of this elevated nitrate is debated, so this research team is collecting data to explore one potential source of nitrate – microorganisms!
Microorganisms have many unique and varied metabolisms, allowing them to exist in unique and varied environments. Some bacteria and archaea on glaciers can convert nitrogen gas (N2) to ammonia (NH4+) and then to nitrate (NO3-). It is possible that similar microorganisms are doing the same thing in these glacially-fed lakes.
Boat and equipment prepared for water sampling on Styggevatnet in August 2025 (photograph: Miranda Seixas).
In order to collect the data necessary for this project, the team drove and hiked to each lake with a small inflatable boat (see picture), allowing them to paddle out to the deepest area. From there, temperature, conductivity, Secchi depth (a proxy for water transparency), and chlorophyll-a concentrations were measured. Water was then collected from two depths, the surface and near-bottom, and filtered back in the lab to collect all microorganisms bigger than 0.2um in diameter. This will be analyzed for DNA back in the United States to identify who is present in the lakes, what they are eating and consuming, and how they are changing the nitrate concentration in the lakes.
Graduate students from the University of Maine, USA, collecting water samples on the glacially-fed lakes Brevatnet and Nigardsbrevatnet in August 2025 (photographs: Kayla Guthrie and Miranda Seixas).
As part of a larger comparative study this data will be compared with data from glacially-fed lakes in Greenland, to determine if there are regional differences in the microbial communities present.