Article

Iron biogeochemistry across marine systems – progress from the past decade

Biogeosciences (Impact Factor: 3.75). 01/2010; DOI:10.5194/bg-7-1075-2010
Source: DOAJ

ABSTRACT Based on an international workshop (Gothenburg, 14–16 May 2008), this review article aims to combine interdisciplinary knowledge from coastal and open ocean research on iron biogeochemistry. The major scientific findings of the past decade are structured into sections on natural and artificial iron fertilization, iron inputs into coastal and estuarine systems, colloidal iron and organic matter, and biological processes. Potential effects of global climate change, particularly ocean acidification, on iron biogeochemistry are discussed. The findings are synthesized into recommendations for future research areas.

0 0
 · 
0 Bookmarks
 · 
76 Views
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Research into the effects of ocean acidification (OA) on marine organisms has greatly increased during the past decade, as realization of the potential dramatic impacts has grown. Studies have revealed the multifarious respon-ses of organisms to OA conditions, indicating a high level of intra-and interspecific variation in species' ability to accommodate these alterations. If we are to provide policy makers with sound, scientific input regarding the expected consequences of OA, we need a broader understanding of these predicted changes. As a group of 20 multi-disci-plinary postgraduate students from around the globe, with a study focus on OA, we are a strong representation of 'next generation' scientists in this field. In this unique cumulative paper, we review knowledge gaps in terms of assessing the biological impacts of OA, outlining directions for future research.
    Marine Biology 08/2012; 160:1789-1805. · 2.47 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Rising atmospheric CO2 is acidifying the surface ocean, a process which is expected to greatly influence the chemistry and biology of the future ocean. Following the development of iron-replete phytoplankton blooms in a coastal mesocosm experiment at 350, 700, and 1050 μatm pCO2, we observed significant increases in dissolved iron concentrations, Fe(II) concentrations, and Fe(II) half-life times during and after the peak of blooms in response to CO2 enrichment and concomitant lowering of pH, suggesting increased iron bioavailability. If applicable to the open ocean this may provide a negative feedback mechanism to the rising atmospheric CO2 by stimulating marine primary production.
    Biogeosciences 01/2010; · 3.75 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Trichodesmium, a filamentous dinitrogen-fixing cyanobac-terium, forms extensive blooms in nutrient-poor tropical and subtropical ocean waters. These cyano-bacteria contribute sig-nificantly to biological fixation of nitrogen from the atmosphere in these waters, and thereby fuel primary production and influence nutrient flow and the cycling of organic and inorganic matter 1,2 . Trichodesmium blooms require large quantities of iron, which is partly supplied by the influx of wind-blown dust 3 . However, the processes and mechanisms associated with dust acquisition are poorly understood 3–6 . Here, we incubate natural populations and laboratory cultures of Trichodesmium with isotopically labelled iron oxides and desert dust, to determine how these cyanobacteria collect, process and use particulate iron. We show that, like most phytoplankton, Trichodesmium acquires only dissolved iron. However, unlike other studied phytoplankton, Trichodesmium accelerates the rate of iron dissolution from oxides and dust, through as yet unspecified cell-surface processes, and thereby increases cellular iron up-take rates. We show that natural puff (ball-shaped) colonies of Trichodesmium are particularly effective at dissolving dust and oxides, which we attribute to efficient dust trapping in their intricate colony morphology, followed by active shut-tling and packaging of the dust within the colony core. We suggest that colony formation in Trichodesmium is an adap-tive strategy that enhances iron acquisition from particulate sources such as dust. The extensive surface blooms of Trichodesmium, easily observed by satellite in the subtropical and tropical oligotrophic oceans, have piqued the curiosity of many scientists as early as Darwin 7 . Trichodesmium blooms comprise tuft-and puff-shaped colonies composed of tens to thousands of individual filaments (trichomes) as well as single, free-floating, trichomes 8 . Colony formation in phytoplankton may increase buoyancy and facilitate vertical migration, decrease grazing, and allow for the development of differentiated cells such as akinetes and heterocysts 9,10 . The formation of puff and tuft colonies has also been speculated to enable Trichodesmium to lower the oxygen concentrations in the centre of the colony and thereby alleviate the inhibitory effect of oxygen on N 2 fixation 11 . However, the large colony size also imposes a strong limitation on dissolved nutrient acquisition. To overcome its size-dependent diffusion limitation with regards to dissolved iron 12 , it has been suggested that Trichodesmium uses aeolian dust as an additional source of iron 13,14 . Indeed, dust inputs to the surface ocean have been correlated with Trichodesmium abundance and elevated N 2 fixation rates 15–17 . Nonetheless, the mechanisms and rates by which Trichodesmium acquire iron from aeolian dust are poorly defined at present, hindering the modelling and prediction of Trichodesmium's response to changes
    Nature Geoscience 06/2011; 4(4):529–534. · 12.37 Impact Factor

Full-text (2 Sources)

View
30 Downloads
Available from
Sep 29, 2012