Abstract
The changing Arctic environment is affecting zooplankton that support its abundant wildlife. We examined how these changes are influencing a key zooplankton species, Calanus finmarchicus, principally found in the North Atlantic but expatriated to the Arctic. Close to the ice-edge in the Fram Strait, we identified areas that, since the 1980s, are increasingly favourable to C. finmarchicus. Field-sampling revealed part of the population there to be capable of amassing enough reserves to overwinter. Early developmental stages were also present in early summer, suggesting successful local recruitment. This extension to suitable C. finmarchicus habitat is most likely facilitated by the long-term retreat of the ice-edge, allowing phytoplankton to bloom earlier and for longer and through higher temperatures increasing copepod developmental rates. The increased capacity for this species to complete its life-cycle and prosper in the Fram Strait can change community structure, with large consequences to regional food-webs.
Highlights
The Arctic is experiencing the strongest warming on the planet and, in recent decades, an unprecedented loss of sea ice (Stroeve and Notz 2018)
Our ecological niche modelling indicated a widespread increase in suitable habitat for C. finmarchicus since the 1980s, spanning much of the northern region of the Fram Strait stretching from the north-western tip of Svalbard and across to the Greenland Shelf (Fig. 2)
Calanus abundance increases progressively from stations S1 to S3, with highest values being observed during late summer (Table 1). 16S meta-barcoding analyses indicated that C. glacialis were almost a negligible part of the population in the upper 200 m at all three stations while C. hyperboreus were only present in this part of the water column in the early summer
Summary
The Arctic is experiencing the strongest warming on the planet and, in recent decades, an unprecedented loss of sea ice (Stroeve and Notz 2018). Arctic warming is not uniform, but amplified in certain regions, such as where there is enhanced inflow of warm Atlantic water into the
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