Submesoscale ocean fronts act as biological hotspot for southern elephant seal

Lia Siegelman (1, 2, 3) , Malcolm O’toole (4) , Mar Flexas (3) , Pascal Rivière (1) , Patrice Klein (2, 3)

1 LEMAR - Laboratoire des Sciences de l'Environnement Marin (LEMAR)
2 JPL - Jet Propulsion Laboratory
3 ESE - Department of Environmental Science and Engineering [Pasadena]
4 The UWA Oceans Institute

The area west of the Kerguelen Islands (20–70°E/45–60°S) is characterized by a weak mesoscale activity except for a standing meander region of the Antarctic Circumpolar Current (ACC) localized between 20 and 40°E. A unique bio-physical dataset at high-resolution collected by a southern elephant seal (Mirounga leonina) reveals a conspicuous increase in foraging activity at the standing meander site up to 5 times larger than during the rest of her three-month trip west of the Kerguelen Islands. Here, we propose a physical explanation for such high biological activity based on the study of small-scale fronts with scales of 5 to 20 km, also called submesoscales. The standing meander is associated with intensified frontal dynamics at submesoscale, not observed in the rest of the region. Results shed new light on the spatial distribution of submesoscale fronts in the under-sampled area west of the Kerguelen plateau and emphasize their importance for upper trophic levels. Despite that most elephant seals target foraging grounds east of the Kerguelen Plateau, our findings suggest that excursions to the west are not accidental, and may be explained by the recurrently elevated physical and biological activity of the site. As such, other standing meanders of the ACC may also act as biological hotspots where trophic interactions are stimulated by submesoscale turbulence.

Mots clés: ACL; ANTARCTIC CIRCUMPOLAR CURRENT; AREA-RESTRICTED SEARCH; FORAGING BEHAVIOR; MIROUNGA-LEONINA; MESOSCALE; PREDATOR; VARIABILITY; TURBULENCE; FEATURES; PASSAGE

Domaines: Biodiversité et Ecologie; Océan, Atmosphère

Lia Siegelman, Malcolm O’toole, Mar Flexas, Pascal Rivière, Patrice Klein. Submesoscale ocean fronts act as biological hotspot for southern elephant seal. Scientific Reports, 2019, 9, pp.5588. ⟨10.1038/s41598-019-42117-w⟩. ⟨hal-02874962⟩