MEPS 581:215-227 (2017)  -  DOI:

Marine predators and phytoplankton: how elephant seals use the recurrent Kerguelen plume

Malcolm O’Toole1,*, Christophe Guinet2, Mary-Anne Lea1,3, Mark A. Hindell1,3 

1Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7001, Australia
2Marine Predator Department, Centre d’études biologiques de Chizé, Villiers-en-Bois 79360, France
3Antarctic Climate and Ecosystems CRC, Hobart, TAS 7001, Australia
*Corresponding author:

ABSTRACT: Predators feeding in a highly dynamic environment have evolved strategies to respond to patchy resource distribution. However, studying these ecological interactions is challenging in the marine environment, as both predators and elements in their environment are often highly mobile and difficult to monitor. We used sensors deployed on female southern elephant seals Mirounga leonina to collect data as they foraged hundreds of metres below a large recurrent phytoplankton plume east of the Kerguelen Islands (49°15’S, 69°10’E). Data collected by animal-borne light sensors were used to reconstruct phytoplankton patterns encountered by the seals. Prey encounter events (PEEs) recorded by seal-borne accelerometers below the euphotic zone were compared with phytoplankton estimates at 2 scales: mesoscale (10s to 100s km) and small scale (inter-dive). These analyses were performed on data recorded during daylight hours only, and did not include data at night due to the sensitivity threshold of the light sensors. Our results showed that elephant seals moved through alternating patches of high- and low-density phytoplankton, but the timing and locations of these bloom patches were different between the upper and lower euphotic layers. Seals recorded more PEEs and shallower dives below high-density patches of phytoplankton. We propose that phytoplankton density at the mesoscale facilitates prey aggregation (direct effect). However, phytoplankton density between dives (small scale) likely facilitates vertical access to prey via the shading effect of phytoplankton (indirect effect). Our study shows how a deep-diving marine predator may use its environment to maximise net energy intake, and we demonstrate its resilience in a highly dynamic ecosystem.

KEY WORDS: Mirounga leonina · Foraging strategy · Prey encounter events · Dive behaviour · Kerguelen phytoplankton plume · Prey access

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Cite this article as: O’Toole M, Guinet C, Lea MA, Hindell MA (2017) Marine predators and phytoplankton: how elephant seals use the recurrent Kerguelen plume. Mar Ecol Prog Ser 581:215-227.

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