Patterns And Controls Of Algal Growth In A Tundra Stream Network (Kärkevagge, Kiruna)

Sammanfattning

The Arctic region is warming at a much higher rate than the rest of the Earth due to global warming. This warming of the Arctic will most likely affect the nutrient fluxes in naturally oligotrophic waterways and streams. This study aimed to examine how these nutrients and abiotic factors affect algal biomass and growth in oligotrophic freshwater streams in the catchment of Kärkevagge, Kiruna. The field work was conducted during the summer of 2025 where 20 study sites were visited two times for measuring nutrient levels, DOC, temperature, oxygen levels etc. and algal biofilm growth on benthic rocks and ceramic tiles. The average biomass was similar across surfaces, with 0.848 µg/cm3 on rocks and 0.769 µg/cm3 on ceramic tiles. The nutrient levels varied throughout the catchment, but the average DIN concentration was 29.7/µg/L. Two multiple regressions were constructed to examine how the biofilm accrual is affected by the measured predictor variables. The results indicated that PO43+ was strongly positively correlated with the biomass growth and the partial effects of both NO3- and NH4+ showed a significant negative correlation. The average N:P ratio was 55:1 which is interpreted as a main limitation of P in the system, however a colimitation is likely as several nearby catchments are primarily N limited. In summary, the result of the study is pointing towards a limitation of P in the Kärkevagge catchment, possibly in colimitation with N.