Abstract
Antarctic coastal polynyas are regions of persistent open water and are thought to be key bio-physical features within the sea-ice zone. However, their use by the upper trophic levels of ecosystems remains unclear. A unique bio-physical dataset recorded by southern elephant seals reveals that East Antarctic polynyas are a key winter foraging habitat for male seals. During their post-moult trips from Isles Kerguelen to the Antarctic continental shelf, a total of 18 out of 23 seals visited 9 different polynyas, spending on average 25 ± 20% (up to 75%) of their total trip time inside polynyas. Changes in seal foraging and diving behaviours are observed inside polynyas as compared to outside polynyas. Two polynya usages by seals are observed for the inactive and active polynya phases, pointing to different seasonal peaks in prey abundance. During the active polynya phase, we link seal foraging behaviour to changes in the physical stability of the water-column, which likely impact the seasonal biological dynamics within polynyas.
Highlights
Previous studies have investigated the timing of primary production within Antarctic polynyas and the controlling environmental factors (e.g.4,13, and[14])
Seal behaviour and polynya use varied between individuals (Table S1): seals spent between 4 to 75% of their total trip inside polynyas, comprising up to 86% of their total time spent over the Antarctic slope/shelf region
We found no clear link between polynya size and the daily average of hunting time per dive (Supplementary, Fig. S3s)
Summary
Previous studies have investigated the timing of primary production within Antarctic polynyas and the controlling environmental factors (e.g.4,13, and[14]). The seasonal usage of polynyas by mid- to upper trophic levels is still poorly known (except for the massive Ross Sea polynya which is well documented and studied, e.g.12), as are the underlying biophysical mechanisms that make these regions profitable for foraging It is unclear if and how marine mammals and seabirds use polynyas either as an air-breathing refuge or as foraging habitat during winter. Male SES can remain over the Antarctic shelf despite dense and persistent pack and fast ice, and it has been hypothesized they might use open water areas between the pack and the fast ice[19,32,33] Within coastal polynyas, they are able to take advantage of both the enriched ecosystems and permanent breathing access during the winter season. We analysed subadult male SES at-sea movements and diving behaviour collected over eleven years (seven years of tracking from 2004 to 2014) to assess (i) whether polynyas were used by SES and if so, the specific timing, (ii) diving behaviour inside polynyas to examine whether they are more favourable foraging grounds than the surrounding shelf/slope areas; and, (iii) the seasonal oceanographic conditions that make these habitats more suitable than adjacent waters
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
