Abstract
Polynyas are areas of open water surrounded by sea ice and are important sources of primary production in high-latitude marine ecosystems. The magnitude of annual primary production in polynyas is controlled by the amount of exposure to solar radiation and sensitivity to changes in sea-ice extent. The degree of coupling between primary production and production by upper trophic-level consumers in these environments is not well understood, which prevents reliable predictions about population trajectories for species at higher trophic levels under potential future climate scenarios. In this study, we find a strong, positive relationship between annual primary production in an Antarctic polynya and pup production by ice-dependent Weddell seals. The timing of the relationship suggests reproductive effort increases to take advantage of high primary production occurring in the months after the birth pulse. Though the proximate causal mechanism is unknown, our results indicate tight coupling between organisms at disparate trophic levels on a short timescale, deepen our understanding of marine ecosystem processes, and raise interesting questions about why such coupling exists and what implications it has for understanding high-latitude ecosystems.
Highlights
High-latitude marine environments are subject to extreme variations in both photoperiod and amount of open water as the extent of sea ice seasonally expands and contracts [1,2,3,4]
Our results suggest the number of pups is strongly, positively associated with primary production in the McMurdo Sound polynya and less strongly, negatively associated with the Ross Sea polynya
In the Ross Sea polynya, the surge in phytoplankton abundance each spring, which is responsible for increased primary production, is thought to be effectively decoupled from the grazing pressure exerted by zooplankton [32,34]
Summary
High-latitude marine environments are subject to extreme variations in both photoperiod and amount of open water as the extent of sea ice seasonally expands and contracts [1,2,3,4]. In the sea-ice zones of both polar oceans, polynyas are recurrent regions of open water surrounded by ice [10] They have long been associated with large numbers of marine mammals and birds and increased amounts of primary production relative to proximal ice-covered areas [11,12]. All polynyas in the Antarctic occur south of the Antarctic Circle experience minimal sunlight and are non-productive during the polar winter [13] In both polar oceans, they remain biologically important even as the surrounding sea ice melts in the polar spring. They remain biologically important even as the surrounding sea ice melts in the polar spring During this time, polynyas are the first areas exposed to the increasing sunlight and are a comparatively localized source of increased primary production in polar oceans [12,14]
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