Factors Controlling the Lack of Phytoplankton Biomass in Naturally Iron Fertilized Waters Near Heard and McDonald Islands in the Southern Ocean

The Kerguelen Plateau is one of the regions in the Southern Ocean where spatially large algal blooms occur annually due to natural iron fertilization. The analysis of ocean color data as well as in situ samples collected during the Heard Earth-Ocean-Biosphere Interactions (HEOBI) voyage in January a...

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Bibliographic Details
Published in:Frontiers in Marine Science
Main Authors: Bożena Wojtasiewicz, Thomas W. Trull, Lesley Clementson, Diana M. Davies, Nicole L. Patten, Christina Schallenberg, Nick J. Hardman-Mountford
Format: Article in Journal/Newspaper
Language:English
Published: Frontiers Media S.A. 2019
Subjects:
Southern Ocean
Heard Island
iron fertilization
phytoplankton
chlorophyll
backscattering
Science
Q
General. Including nature conservation
geographical distribution
QH1-199.5
Antarctic
Heard
Kerguelen
McDonald Islands
The Antarctic
Antarc*
Online Access:https://doi.org/10.3389/fmars.2019.00531
https://doaj.org/article/279453a84f0846eaa870aa7967975e55
Description
Summary:The Kerguelen Plateau is one of the regions in the Southern Ocean where spatially large algal blooms occur annually due to natural iron fertilization. The analysis of ocean color data as well as in situ samples collected during the Heard Earth-Ocean-Biosphere Interactions (HEOBI) voyage in January and February 2016, surprisingly revealed that chlorophyll a concentrations in waters located close to Heard and McDonald islands were much lower than those on the central Kerguelen Plateau. This occurs despite high levels of both glacial and volcanic iron supply from these islands. The analysis of pigment and optical data also indicated a shift in the phytoplankton size structure in this region, from a microphytoplankton to nanophytoplankton dominated community. Possible explanations for this high nutrient, high iron (Fe), low chlorophyll (HNHFeLC) phenomenon were explored. Low light availability due to deep mixing and shading by re-suspended sediment particles and augmented by dilution with surrounding low chlorophyll waters in the Antarctic Circumpolar Current was shown to be an important mechanism shaping phytoplankton communities. The competing dynamics between stimulation and limitation illustrate the complexity of short-term responses to our changing climate and cryosphere.

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