Abstract
Climate change is impacting ice-affiliated marine mammal habitats throughout the Arctic, with sea ice declines reducing traditional haul-out and breeding habitats, putting a premium on alternative useable areas. In the Arctic, ice forms early in the season and is retained late into the spring in coastal lagoons, but little information is available regarding how this nature type is used by marine mammals. This study documents use of a lagoon by 20 ringed seals tracked for an average of 188 d via satellite-linked GPS tags. Overall, tagged seals spent 8.9 ± 0.4% (±SD) of their time per day inside the lagoon, with strong summer and autumn peaks that dropped off in winter and ceased in spring. Inside the lagoon, seals spent significantly larger proportions of their time hauled out and less time diving in comparison to when they were outside the lagoon. Additionally, the seals dove deeper (19 vs. 7 m) and for longer periods (4 vs. 2.5 min) when outside the lagoon, indicating that most feeding took place out in the fjord. However, residency periods in the lagoon of up to 43 d as well as more intense diving than would be expected for transport to and from haul-out areas within the lagoon suggest that ringed seals also feed in the lagoon. Regular opportunistic sightings of ringed seals in lagoons around Svalbard, Norway, together with the quantitative behavioural documentation of lagoon use in the present study, suggest that lagoons may serve as refugia areas, which might become increasingly important as climate change continues to alter Arctic marine ecosystems.
Highlights
Lagoons are shallow, coastal bodies of water separated from the ocean by a barrier, but connected at least intermittently to the ocean by one or more restricted inlets (Kjerfve 1994)
The present study quantitatively explored the use of lagoons by the most numerous of these seal species in Svalbard, the ringed seal, to document seasonal use and shed light on the potential importance of this habitat for this climate-change-sensitive species
Investigating habitat use within unique nature types, such as lagoons, is crucial to understanding ecosystem function and potential climate change responses by marine animals. This is especially true in polar environments, where environmental change is already severe and is expected to have dramatic consequences on habitat use by marine animals
Summary
Coastal bodies of water separated from the ocean by a barrier, but connected at least intermittently to the ocean by one or more restricted inlets (Kjerfve 1994). Lagoons are subject to tidal mixing, where seawater mixes with freshwater from their land-based catchments (Garrido et al 2011). Some invertebrate and fish species spawn in the open sea where salinities are constant, but juvenile life stages migrate into lagoons where they benefit from the calm conditions and plentiful food resources (Kathiresan & Bingham 2001, Heck et al 2003, Kennish & Paerl 2010). This rich diversity of lower trophic animals is thought to make lagoons favourable foraging environments for marine predators, such as birds and marine mammals (Paiva et al 2008)
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