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Pelagic iron recycling in the Southern Ocean: exploring the contribution of marine animals

Citation

Ratnarajah, L and Nicol, S and Bowie, AR, Pelagic iron recycling in the Southern Ocean: exploring the contribution of marine animals, Frontiers in Marine Science, 5 Article 109. ISSN 2296-7745 (2018) [Refereed Article]


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Copyright Statement

Copyright 2018 Ratnarajah, Nicol and Bowie. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/

DOI: doi:10.3389/fmars.2018.00109

Abstract

The availability of iron controls primary productivity in large areas of the Southern Ocean. Iron is largely supplied via atmospheric dust deposition, melting ice, the weathering of shelf sediments, upwelling, sediment resuspension, mixing (deep water, biogenic, and vertical mixing) and hydrothermal vents with varying degrees of temporal and spatial importance. However, large areas of the Southern Ocean are remote from these sources, leading to regions of low primary productivity. Recent studies suggest that recycling of iron by animals in the surface layer could enhance primary productivity in the Southern Ocean. The aim of this review is to provide a quantitative and qualitative assessment of the current literature on pelagic iron recycling by marine animals in the Southern Ocean and highlight the next steps forward in quantifying the retention and recycling of iron by higher trophic levels in the Southern Ocean. Phytoplankton utilize the iron in seawater to meet their metabolic demand. Through grazing, pelagic herbivores transfer the iron in phytoplankton cells into their body tissues and organs. Herbivores can recycle iron through inefficient feeding behavior that release iron into the water before ingestion, and through the release of fecal pellets. The iron stored within herbivores is transferred to higher trophic levels when they are consumed. When predators consume iron beyond their metabolic demand it is either excreted or defecated. Waste products from pelagic vertebrates can thus contain high concentrations of iron which may be in a form that is available to phytoplankton. Bioavailability of fecal iron for phytoplankton growth is influenced by a combination of the size of the fecal particle, presence of organic ligands, the oxidation state of the iron, as well as biological (e.g., remineralization, coprochaly, coprorhexy, and coprophagy) and physical (e.g., dissolution, fragmentation) processes that lead to the degradation and release of fecal iron. The flux of dissolved iron from pelagic recycling is comparable to other sources in the region such as atmospheric dust, vertical diffusivity, vertical flux, lateral flux and upwelling, but lower than sea ice, icebergs, sediment resuspension, and deep winter mixing. The temporal and seasonal importance of these various factors requires further examination.

Item Details

Item Type:Refereed Article
Keywords:iron, recycling, Southern Ocean, marine animals, biological carbon pump, carbon, Southern Ocean, biological recycling
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Biological Oceanography
Objective Division:Environment
Objective Group:Ecosystem Assessment and Management
Objective Field:Ecosystem Assessment and Management of Antarctic and Sub-Antarctic Environments
UTAS Author:Ratnarajah, L (Miss Lavenia Ratnarajah)
UTAS Author:Nicol, S (Dr Stephen Nicol)
UTAS Author:Bowie, AR (Associate Professor Andrew Bowie)
ID Code:130958
Year Published:2018
Web of Science® Times Cited:1
Deposited By:Oceans and Cryosphere
Deposited On:2019-02-21
Last Modified:2019-03-12
Downloads:17 View Download Statistics

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