Nitrogen Fixation in Arctic Coastal Waters (Qeqertarsuaq, West Greenland): Influence of Glacial Melt on Diazotrophs, Nutrient Availability, and Seasonal Blooms

The Arctic Ocean is experiencing rapid changes driven by climate change, with decreasing sea ice and glacial meltwater altering biogeochemical conditions. These transformations are expected to enhance primary productivity, but the availability of nitrogen—a key nutrient often limiting growth—remains a critical factor. While dinitrogen (N₂) fixation, mediated by diazotrophs, is well-studied in tropical and subtropical oceans, its role in Arctic waters has only recently gained attention. This study addresses gaps in our understanding of N₂ fixation rates, diazotrophic communities, and their environmental drivers in Arctic coastal waters, focusing on fjords and seas influenced by glacial meltwater.

Using isotope labeling, genetic analyses, and biogeochemical profiling, we observed N₂ fixation rates ranging from 0.16 to 2.71 nmol N L⁻¹ d⁻¹, substantially higher than those reported in many oceanic regions. UCYN-A dominated the diazotrophic community. Our findings revealed peak N₂ fixation rates co-occurring with maximum chlorophyll a concentrations and primary production rates near the Vaigat Strait, a region strongly influenced by glacier meltwater. We propose that glacial melting and nutrient influx in the Vaigat Strait enhanced primary productivity, creating a niche for diazotrophs to thrive, with the potential to sustain and extend such blooms.

These results highlight the previously underappreciated significance of N₂ fixation in Arctic coastal waters and its potential response to ongoing climate-driven changes, including the melting of polar ice. By shedding light on the physical and biogeochemical processes shaping nitrogen availability and primary productivity in Greenland’s fjords and coastal seas, this study contributes to understanding the region’s evolving ecosystem dynamics.