[OANNES Foro] Retention of plankton within ocean eddies

[Mario Cabrejos]

Global Ecology and Biogeography

.         First published: 22 June 2016 

.         DOI: 10.1111/geb.12485 


 


Retention of plankton within ocean eddies


.         Scott Condie, Ryan Condie


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Abstract


Aim


Mesoscale ocean eddies (closed circular currents typically 100-300 km in
diameter) are ubiquitous features of the world's oceans. They form partially
isolated environments with distinct physical and chemical conditions capable
of supporting and transporting whole plankton communities. The productivity
and biodiversity of these communities is ultimately dependent on an eddy's
ability to retain planktonic organisms. Our aim was to estimate eddy
retention time-scales across a range of oceanic environments and larval
behaviours, with implications for both distributions and future changes in
plankton communities.

 


Location


The Pacific Ocean, Indian Ocean, Southern Ocean and Mediterranean Sea.

 


Methods


A particle-tracking model was forced using ocean currents from a number of
validated hydrodynamic models covering environments ranging from shelf seas
to the open ocean and equatorial to high-latitude waters. Eddies were seeded
with large numbers of particles and their rate of loss from the eddy was
used to estimate retention times. The influences of common plankton swimming
behaviours were explicitly captured in the model.

 


Results


Eddy retention times of modelled plankton ranged from 5 to 67 days, with a
median of 19 days. Retention times were not correlated with latitude or eddy
size. However, plankton residing near the surface of eddies rotating
cyclonically (anticlockwise in the Northern Hemisphere) had significantly
shorter retention times than those residing in the same eddy at depth, and
vice versa for eddies rotating anticyclonically.

 


Main conclusions


We show that ocean eddies have the potential to retain and support
planktonic (and even nektonic) communities over many generations and are
likely to enhance larval survival for many invertebrate and fish species.
Differences in retention with depth suggest that cyclonic and anticyclonic
eddies will support differing plankton communities. If their relative
geographical distributions change with global climate, then the relative
proportions of diatom-based and dinoflagellate-based communities may also
change, with potential implications for higher trophic animals.

 



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