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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2016-53
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/bg-2016-53
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Submitted as: research article 17 Mar 2016

Submitted as: research article | 17 Mar 2016

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The revised manuscript was not accepted.

Lagrangian characterization of nitrate supply and episodes of extreme phytoplankton blooms in the Great Australian Bight

Paulina Cetina-Heredia1,2, Erik van Sebille1,2, Richard Matear3, and Moninya Roughan4 Paulina Cetina-Heredia et al.
  • 1Climate Change Research Centre, ARC Centre of Excellence for Climate System Science, UNSW Australia, Sydney Australia
  • 2Grantham Institute & Department of Physics, Imperial College London, London, United Kingdom
  • 3CSIRO Marine and Atmospheric Research, CSIRO Marine Laboratories, Hobart, Australia
  • 4Regional and Coastal Oceanography Laboratory, School of Mathematics and Statistics, UNSW Australia, Sydney, Australia

Abstract. Phytoplankton growth is the foundation for energy transfer into higher trophic levels, influences climate by the uptake of atmospheric CO2, and plays an important role in nutrient cycling. Here we use a novel lagrangian approach to characterize the nitrate supply to the Great Australian Bight, identify episodes of extreme phytoplankton blooms and ascertain the origin of the nitrate sources that fuel them. We find that 55 % of nitrate used by phytoplankton enters the GAB in the upper 100 m and that 88 % originates locally from a region between the GAB and the Sub Antarctic Front, rather than from more remote oceans; thus, most of the nitrate is recycled locally. Our results show extreme phytoplankton blooms have an annual periodicity, peaking in the Austral autumn when the mixed layer deepens. This suggests that stratification erosion is key supplying nutrients into the euphotic zone and triggering these episodes.

Paulina Cetina-Heredia et al.
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Paulina Cetina-Heredia et al.
Paulina Cetina-Heredia et al.
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Short summary
Characterizing phytoplankton growth influences fisheries and climate. We use a lagrangian approach to identify phytoplankton blooms in the Great Australian Bight (GAB), and associate them with nitrate sources. We find that 88 % of the nitrate utilized in blooms is originated between the GAB and the SubAntarctic Front. Large nitrate concentrations are supplied at depth but do not reach the euphotic zone often. As a result, 55 % of blooms utilize nitrate supplied in the top 100 m.
Characterizing phytoplankton growth influences fisheries and climate. We use a lagrangian...
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