space time trophic (A)

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Antarctic Studies, University of Tasmania, Hobart, TAS 7001, Australia ... productive water masses in October (B) that extend to important king penguin foraging ...
Tracking ecological hotspots in the Southern Ocean: Antarctic Circumpolar Current as a space-time-trophic conveyer belt Malcolm O’Toole1, Sara Sergi1, Cedric Cotte1, Charles Bost2, Christophe Guinet2, Henri Weimerskirch2, Mark A Hindell3,4, Francesco d’Ovidio1 1Laboratoire

d'Oceanographie et du Climat (LOCEAN-IPSL), Université Pierre et Marie Curie, Paris 75252, France | 2Centre d’études biologiques de Chizé, Villiers-en-Bois 79360, France | 3Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7001, Australia | 4Antarctic Climate and Ecosystems CRC, Hobart, TAS 7001, Australia

Abstract. Satellite data analysis has showed that the environment of the open ocean – uniform and homogeneous to our naked eyes - is in fact populated by strongly contrasted physical features, whose lifetime occurs on ecologically relevant spatial and temporal scales. This dynamical landscape has a primary structuring role on marine ecosystems in particular in the pelagic regions. Pinpointing which physical features are the most ecologically relevant, tracking them, and estimating their lifetime and inter-annual variability are a major challenge for ecologists. Here, we combine bio-logging data and advanced multi-satellite diagnostic tools to track pelagic ecological hotspots in the Indian sector of the Southern Ocean. By clustering predator foraging sites according to diet, we identify five regional hotspots. We interpret these regions by pathways of iron and ageing of the ecosystem from primary production to higher trophic organisms. These results are a first step for the scientific basis of a marine protected area (MPA) proposal to the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR). (2)

Trophic hotspots by bio-logging

(1)

Argos and GPS tracks of nine predator species (N=413) show common foraging grounds according to their diet: (4) 50°E

Fish-squid (2)

53°E

(4)

Prey diet Squid (1)

47°S

Fish-crustacean (3) Fish (4)

(3)

Predator species Wandering albatross (N=139); Sooty albatross (N=6); Light-mantled albatross (N=3) Antarctic fur seal (N=12); Southern elephant seal (N=105); Sooty albatross (N=3); Wandering albatross (N=12); White-chinned petrel (N=5) Macaroni penguin (N=38) Antarctic fur seal (N=45); Black-browed albatross (N=4); King penguin (N=41)

52°S

King penguin foraging hotspot (Jan/Feb)

(A)Bloom October 2005

(i)

(B) Post-bloom January 2006

(ii)

(ii)

As an example of our functional approach, we show here an analysis of the region: (A) Several seamount complexes on the South West Indian Ridge fertilize productive water masses in October (B) that extend to important king penguin foraging hotspot by January. The ‘age’ of water parcels from iron sources was derived by altimetry-based Lagrangian calculations.

(iii)

0.8 mg/m3

(i)

The case for foraging hotspot south of Crozet: ageing of ecosystem by satellite

(ii)

(ii)

i)

Seamounts (e.g. South West Indian Ridge complex - SWIR) neglected as an upstream iron source up until now.

ii)

Phytoplankton bloom patch (0.8 mg/m3) in October correspond to water masses associated with SWIR seamounts 50 days prior.

(iii)

iii) King penguin foraging hotspot in January corresponds to water masses associated with phytoplankton bloom patch 60-90 days prior; advecting a likely enrichment in mid-trophic organisms.

Images: S. Sergi

(i)

(ii)

From iron to predators

(iii)

i)

The Taylor Cap phenomenon [Clark et al. Ann. Rev. Mar. Sci. 2010] – an isopyctal doming effect above a seamount – may allow abyssal iron to reach the mixed layer.

ii)

Horizontal advection and eddy processes transport and aggregate productive water masses eastward.

iii) Energy is transferred up the trophic chain as water masses are advected east over several months: primary producer (phytoplankton)  secondary producer (zooplankton)  mid-trophic prey (myctophid)  top predator (king penguin) Image: S. Sergi

10°E

30°E

50°E space

Oct Iron

1° prod.

2° prod.

mid trophic

Feb time top trophic predator

Thanks to centre national d’études spatiales (CNES) and Laboratoire d'Oceanographie et du Climat (LOCEAN-IPSL) for supporting this postdoctoral fellowship. For contact please email [email protected]