Photo: Patrick Hernvall collecting stones that will later be brushed. The material brushed from the stone surfaces is analysed for the presence of diatoms
As part of the Interreg Aurora funded project Developing Acid Sulfate Soil for Improved Water Management (MASSIW), various impact indicators are being used to demonstrate how acid sulfate soils affect aquatic life in watercourses.
In Västerbotten, Sweden, the primary study area is Flarkån, where the impact of acid sulfate soils is limited upstream but increases downstream in areas where active acid sulfate soils occur. The project also focuses on Tvärån and Högforsån, as well as other coastal watercourses where the effects of acid sulfate soils are already known.
On the opposite side of the Gulf of Bothnia, in Ostrobothnia, Finland, four smaller watercourses are being studied: Penikån, Harvungån, Vörå River, and Kainobäcken. Within their catchment areas, the proportion of acid sulfate soils is estimated to vary between 7 and 40 percent.
The project includes electrofishing, sampling and analysis of diatoms and benthic macroinvertebrates, analyses of physicochemical parameters, and environmental DNA (eDNA) analyses. The results from these investigations will be presented through StoryMaps, illustrating in a concrete way how acid sulfate soils affect aquatic ecosystems.
The use of eDNA to study aquatic environments has become increasingly common as the method has developed. Sampling within the MASSIW project was carried out between 25 and 29 May 2026 in both Sweden and Finland by the Uppsala-based company MIX Research.
Viktor Birgersson from MIX Research explains the eDNA method: “All organisms release DNA into their surroundings, and we can collect and analyse this DNA to identify which species have been present in the water. When collecting DNA samples, there is no need to capture or even touch the organisms. Instead, water is passed through a fine filter, from which DNA is later extracted and analysed in the laboratory.”
Viktor Birgersson displaying a diatom sample
The DNA collected in the filters is preserved by filling the filters with ethanol immediately after filtration. For diatom samples, MIX Research uses a different sampling technique known as the brushing method, where stones are brushed and the material scraped from their surfaces is collected for analysis.
Sampling can be designed in different ways. Within MASSIW, sampling sites were primarily selected where DNA from marine fish species was not expected to occur. In each watercourse, samples were collected both upstream and downstream of areas containing active acid sulfate soils. The analyses will focus on DNA from bony fish, river and brook lampreys, and diatoms.
Interreg Aurora projects provide organisations with opportunities to test newer methods alongside their traditional environmental monitoring programmes—in this case, eDNA technology. Access to this knowledge is valuable for all the organizations participating in the project, extending benefits beyond the project team and the duration of the project itself.
In connection with the eDNA sampling in Finland, water samples were also collected for metal analyses. After returning from the field, the samples were processed through steps including filtration and acid preservation before being sent to Åbo Akademi University, where the project team analysed them. The metal analyses help determine whether metals that may have been leached from soils due to low pH levels are present in the water.
The fieldwork in Finland was carried out by Viktor Birgersson and Patrick Hernvall from MIX Research, together with Jenny Viklund from the County Administrative Board of Västerbotten and Heidi Smart from the Economic Development Centre of South Ostrobothnia. During the field work in Sweden, Heidi Smart was replaced by Jan Åberg from the County Administrative Board of Västerbotten. In Sweden, samples were also collected for the Interreg Aurora project HIDDEN and for a project focusing on jointly owned minor roads and culverts.
Jenny Viklund and Heidi Smart found it valuable to work together on practical field sampling
The collaboration across the Gulf of Bothnia worked exceptionally well, from procurement to field sampling, and the project staff is looking forward to sharing the results of the eDNA analyses later this year.
Learn more about the project MASSIW
