Sediment trap samples reveal regional differences in the population structure of Calanus hyperboreus from the Arctic Ocean.

This article focuses on the regional differences in seasonal population dynamics of *Calanus hyperboreus*, a dominant Arctic copepod species, using time-series sediment trap data from three Arctic Ocean regions: the eastern Fram Strait, northern Chukchi Sea, and MacKenzie Trough. The study found that the timing of the copepods’ seasonal vertical migration (SVM) ascent from overwintering depths to the surface was similar across regions (April–May), while the descent back to depth varied regionally, occurring earliest in the Fram Strait and later in the Chukchi Sea and MacKenzie Trough. Population fluxes and developmental stage compositions differed among locations, suggesting variations in life cycle duration and local reproduction, with the largest population observed in the MacKenzie Trough. The findings highlight how environmental factors such as sea-ice coverage, water temperature, and primary production influence *C. hyperboreus* life history traits and underscore the potential impacts of climate change on this key Arctic zooplankton species.