Iron study during a time series in the western Weddell pack ice

Lannuzel, Delphine; Schoemann, Véronique; Jong, Jeroen de; Chou, Lei; Delille, Bruno; Becquevort, Sylvie; Tison, Jean-Louis

doi:10.1016/j.marchem.2007.10.006

Cited by 139 publications

(167 citation statements)

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“…In fact about half the total iceberg discharge volume is made up of giant icebergs 15 those exceeding 18 km in horizontal dimension -and there have currently only been two observational studies of the phytoplankton blooms close to individual giant icebergs, both in conditions within or near sea-ice cover in the Weddell Sea 1,3 . Such areas may be subject to enhanced productivity due to the impact of sea-ice fertilization 16 . While the calving of giant icebergs is very episodic 15 , they derive from a range of geographical and geological environments around Antarctica, and thus likely have different iron and nutrient characteristics.…”

mentioning

confidence: 99%

Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs

2016

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The Southern Ocean is a significant sink in the ocean component of the global carbon cycle, contributing ~ 10% of the ocean's total carbon sequestration through a mixture of chemical and biologically-driven processes 5 . However, its contribution is at a lower level than that of the smaller South Pacific and Indian Oceans 5 , due to its low concentration of dissolved iron, an important trace nutrient for primary production 6 . Atmospheric dust is a major background source of iron to the region 7 , but iron-rich sediment fluxes from islands 8 , continental shelves 9 , ice sheet meltwater 10 and melting icebergs 1 are known to be other, locally much more important, sources of iron. There are a few large-scale estimates of the contribution of icebergs to the Southern Ocean iron flux, derived from modelling studies of typical sub-kilometre sized icebergs 11,12 , scaling up of observational studies 13,14 or remote sensing studies 2 . However, these assume iceberg inputs are well represented by those from the smaller, sub-kilometre, peak in the very bimodal size distribution 15 . In fact about half the total iceberg discharge volume is made up of giant icebergs 15 -those exceeding 18 km in horizontal dimension -and there have currently only been two observational studies of the phytoplankton blooms close to individual giant icebergs, both in conditions within or near sea-ice cover in the Weddell Sea 1, 3 . Such areas may be subject to enhanced productivity due to the impact of sea-ice fertilization 16 . While the calving of giant icebergs is very episodic 15 , they derive from a range of geographical and geological environments around Antarctica, and thus likely have different iron and nutrient characteristics. Several dozen such icebergs are present in the Southern Ocean at any one time 15 , and they can survive for many years. Even when in areas of open water giant icebergs can survive for longer than a year 17 . Here we examine the chlorophyll signature from a range of giant icebergs in the open Southern Ocean using remote sensing, to show that ocean fertilization from such icebergs is much larger than previously suspected.Chlorophyll levels are well known to be raised near icebergs 1,2,18 . This derives from the meltwater plumes from icebergs containing significant concentrations of iron, but also a range of other nutrients 14 . As the Southern Ocean is a High Nutrient Low Chlorophyll (HNLC) region 6 , it is the bioavailable iron known to be in nanoparticle aggregates of ferrihydrite and goethite in iceberg sediments 13 that is the key nutrient within this meltwater. Dissolution of these particles leads to enriched concentrations of dissolved iron in the meltwater plume at levels 10-1000 times those due to atmospheric dust 19 . Ship-based studies have demonstrated that, for an iceberg of maximum horizontal size L i , chlorophyll levels are enhanced downstream over a distance of ~ L i 20 . Similarly, it has been shown using SeaWifs ocean colour that the probability of chlorophyll being enhanced 6 days after an iceb...

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confidence: 99%

Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs

2016

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“…Lannuzel et al 2007;Becquevort et al 2009;van de Merwe et al 2011a, b), large accumulation in sea ice of both organic matter and Fe was reported during the ISPOL survey (Table 2; Arrigo and Thomas 2004;Lannuzel et al 2008;Dumont et al 2009), indicating that sea ice can be a significant source of organic matter and Fe to the phytoplankton-poor and Fe-starved Antarctic surface waters. Dissolved organic matter can originate from melting sea ice but also from excretion by phytoplankton, sea ice algal cell lysis, exudation or sloppy feeding by zooplankton (Kähler et al 1997).…”

Section: Organic Matter and Fementioning

confidence: 89%

“…Detailed thermodynamics and chemical properties of the ISPOL drifting station are presented in Tison et al (2008) and Lannuzel et al (2008). To summarize, the visited ice floe was approximately 90-cm-thick 1 st year sea ice with a 10-cm layer of granular ice (frazil) underlain with columnar ice .…”

Section: Sea Ice Thermodynamicsmentioning

confidence: 99%

Effect of melting Antarctic sea ice on the fate of microbial communities studied in microcosms

et al. 2013

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Although algal growth in the iron-deficient Southern Ocean surface waters is generally low, there is considerable evidence that winter sea ice contains high amounts of iron and organic matter leading to ice-edge blooms during austral spring. We used field observations and shipbased microcosm experiments to study the effect of the seeding by sea ice microorganisms, and the fertilization by organic matter and iron on the planktonic community at the onset of spring/summer in the Weddell Sea. Pack ice was a major source of autotrophs resulting in a ninefold to 27-fold increase in the sea ice-fertilized seawater microcosm compared to the ice-free seawater microcosm. However, heterotrophs were released in lower numbers (only a 2-to 6-fold increase). Pack ice was also an important source of dissolved organic matter for the planktonic community. Small algae (\10 lm) and bacteria released from melting sea ice were able to thrive in seawater. Field observations show that the supply of iron from melting sea ice had occurred well before our arrival onsite, and the supply of iron to the microcosms was therefore low. We finally ran a ''sequential melting'' experiment to monitor the release of ice constituents in seawater. Brine drainage occurred first and was associated with the release of dissolved elements (salts, dissolved organic carbon and dissolved iron). Particulate organic carbon and particulate iron were released with low-salinity waters at a later stage.

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“…First, changes in Fe input rates in the SO could be related to changes in important current sources, including precipitation, atmospheric dust deposition and sea ice melting (e.g., Lizotte, 2001;Lannuzel et al, 2008;Moore and Braucher, 2008;Boyd and Ellwood, 2010). Secondly, warmer temperatures and ocean acidification (OA) will directly affect Fe chemistry, namely its solubility and strength of complexation with organic ligands (Millero, 2009;Breitbarth et al, 2010;Hassler et al, 2013;Gledhill et al, 2015).…”

Section: Iron (Fe) Limitationmentioning

confidence: 99%

Southern Ocean phytoplankton physiology in a changing climate

Petrou

Kranz

Trimborn

et al. 2016

Journal of Plant Physiology

104

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Please cite this article in press as: Petrou, K., et al., Southern Ocean phytoplankton physiology in a changing climate. J Plant Physiol (2016), http://dx.doi.org/10.1016/j.jplph.2016.05.004 ARTICLE IN PRESS a b s t r a c tThe Southern Ocean (SO) is a major sink for anthropogenic atmospheric carbon dioxide (CO 2 ), potentially harbouring even greater potential for additional sequestration of CO 2 through enhanced phytoplankton productivity. In the SO, primary productivity is primarily driven by bottom up processes (physical and chemical conditions) which are spatially and temporally heterogeneous. Due to a paucity of trace metals (such as iron) and high variability in light, much of the SO is characterised by an ecological paradox of high macronutrient concentrations yet uncharacteristically low chlorophyll concentrations. It is expected that with increased anthropogenic CO 2 emissions and the coincident warming, the major physical and chemical process that govern the SO will alter, influencing the biological capacity and functioning of the ecosystem. This review focuses on the SO primary producers and the bottom up processes that underpin their health and productivity. It looks at the major physico-chemical drivers of change in the SO, and based on current physiological knowledge, explores how these changes will likely manifest in phytoplankton, specifically, what are the physiological changes and floristic shifts that are likely to ensue and how this may translate into changes in the carbon sink capacity, net primary productivity and functionality of the SO.

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Iron study during a time series in the western Weddell pack ice

Cited by 139 publications

References 23 publications

Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs

Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs

Effect of melting Antarctic sea ice on the fate of microbial communities studied in microcosms

Southern Ocean phytoplankton physiology in a changing climate

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