| 1. |
- Bey, Ergün, et al.
(författare)
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Ocean acidification reduces iodide production by the marine diatom Chaetoceros sp. (CCMP 1690)
- 2023
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Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 257
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton in marine surface waters play a key role in the global iodine cycle. The biologically-mediated iodide production under future scenarios is limited. Here we compare growth, iodate to iodide conversion rate and membrane permeability in the diatom Chaetoceros sp. (CCMP 1690) grown under seawater carbonate chemistry conditions projected for 2100 (1000 ppm) and pre-industrial (280 ppm) conditions. We found no effect of CO2 on growth rates, but a significantly higher cell yield under high CO2, suggesting sustained growth from relief from carbon limitation. Cell normalised iodate uptake (16.73 +/- 0.92 amol IO3- cell-1) and iodide production (8.61 +/- 0.15 amol I-cell-1) was lower in cultures grown at high pCO2 than those exposed to preindustrial conditions (21.29 +/- 2.37 amol IO3- cell-1, 11.91 +/- 1.49 amol I-cell-1, respectively). Correlating these measurements with membrane permeability, we were able to ascertain that iodide conversion rates were not linked to cell permeability and that the processes of mediated iodate loss and diatom-iodide formation are decoupled. These findings are the first to implicate OA in driving a potential shift in diatom-mediated iodate reduction. If our results are indicative of diatom-mediated iodine cycling in 2100, future surface ocean conditions could experience reduced rates of iodide production by Chaetoceros spp., potentially lowering iodide concentrations in ocean regions dominated by this group. These changes have the potential to impact ozone cycling and new particle formation in the atmosphere.
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| 2. |
- Stolle, Christian, et al.
(författare)
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The MILAN Campaign : Studying Diel Light Effects on the Air–Sea Interface
- 2020
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - 0003-0007 .- 1520-0477. ; 101:2, s. E146-E166
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Tidskriftsartikel (refereegranskat)abstract
- The sea surface microlayer (SML) at the air–sea interface is <1 mm thick, but it is physically, chemically, and biologically distinct from the underlying water and the atmosphere above. Wind-driven turbulence and solar radiation are important drivers of SML physical and biogeochemical properties. Given that the SML is involved in all air–sea exchanges of mass and energy, its response to solar radiation, especially in relation to how it regulates the air–sea exchange of climate-relevant gases and aerosols, is surprisingly poorly characterized. MILAN (Sea Surface Microlayer at Night) was an international, multidisciplinary campaign designed to specifically address this issue. In spring 2017, we deployed diverse sampling platforms (research vessels, radio-controlled catamaran, free-drifting buoy) to study full diel cycles in the coastal North Sea SML and in underlying water, and installed a land-based aerosol sampler. We also carried out concurrent ex situ experiments using several microsensors, a laboratory gas exchange tank, a solar simulator, and a sea spray simulation chamber. In this paper we outline the diversity of approaches employed and some initial results obtained during MILAN. Our observations of diel SML variability show, for example, an influence of (i) changing solar radiation on the quantity and quality of organic material and (ii) diel changes in wind intensity primarily forcing air–sea CO2 exchange. Thus, MILAN underlines the value and the need of multidiciplinary campaigns for integrating SML complexity into the context of air–sea interaction.
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