How Riverine and Glacial Freshwater Controls Hydrography, Nutrients, and Phytoplankton Blooms in Southern Greenland Fjords

Greenland fjords experience strong seasonal productivity that is increasingly affected by Arctic warming and freshwater inputs from precipitation, snowmelt, and glacial melt. We compared two southern Greenland fjords during early snowmelt season - one dominated by riverine discharge from a land-terminating glacier and one influenced by a marine-terminating glacier. The river-influenced site showed earlier spring bloom onset and substantially higher phytoplankton biomass due to combined effects of earlier light availability and riverine nutrient replenishment. These findings highlight the critical role of freshwater source and timing in regulating early-season fjord productivity.