In the Arctic, the fronts of marine-terminating glaciers represent unique ecosystems. Upwelling subglacial discharge plumes and iceberg calving contribute to creating foraging hotspots for animals. However, the dynamics of proglacial-fjord ecosystems are still not well documented. From August 2022 to July 2024, to continuously monitor seasonal changes in the abundance of fish, zooplankton, and icebergs, a 38-kHz upward-looking echosounder was moored at a depth of 230 m near the front of Bowdoin Glacier. A two-year dataset revealed several annual patterns. In summer, a large backscattering strength was observed, caused by sediment-transporting subglacial discharge and iceberg keels. This gradually decreased and reached a minimum between March and June for organisms and between October and July for icebergs. Diel vertical migration (DVM) was observed in spring and autumn: organisms stayed in the deep layer during the day and migrated to the middle layer at night. Different DVM behavior was seen in November 2023, with other aggregations near the surface during the day and in the middle layer at night. These behaviors may indicate prey–predator interactions. Our data from in the vicinity of a glacier front will help clarify the dynamics of a proglacial fjord and its fish-zooplankton ecosystem.
Hasegawa et al. (Wed,) studied this question.