SAMMANSÄTTNING AV MAKROALGER I SVENSKA ÅLGRÄSÄNGAR eDNA spårning och klimatförändringar

The aim of my bachelor’s thesis is to investigate, through a literature review, changes in the distribution of filamentous algae as well as the general species composition of macroalgae and diatoms in Swedish eelgrass meadows. I have also studied the possibility of tracking these algae and diatoms in eelgrass meadows using eDNA methodology. The focus has been on linking these changes to climate change factors such as eutrophication, temperature increase, and anthropogenic emissions, and how these affect the health of eelgrass meadows and their ecosystem services, such as a carbon sink and biodiversity support.The results show that filamentous algae have increased markedly in coverage in Swedish coastal areas between 1980 and 2021, especially in sheltered bays, indicating that altered environmental conditions favor these fast-growing species. Genetic tracking using eDNA demonstrated that there are functional primers for many species, particularly among brown algae and red algae, whereas green algae require more specific primers due to greater genetic variation. Diatoms showed good coverage with several primers, but there are still knowledge gaps regarding genetic resolution for this group, while brown and red algae have broader species coverage with fewer primers. Overall, the work shows that the increase in filamentous algae is clearly linked to climate and environmental changes, which may affect the function and biodiversity of eelgrass meadows. eDNA technology appears to be a promising tool for future monitoring of algal communities in coastal environments, but further development of primers and databases is needed to cover more species and taxonomic groups.