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  • 1
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    Iron limitation of microbial phosphorus acquisition from METEOR cruise M116 (2019)
    PANGAEA
    In:  Supplement to: Browning, Thomas J; Achterberg, Eric Pieter; Yong, Jaw-Chuen; Rapp, Insa; Utermann, Caroline; Engel, Anja; Moore, C M (2017): Iron limitation of microbial phosphorus acquisition in the tropical North Atlantic. Nature Communications, 8(1), 15465, https://doi.org/10.1038/ncomms15465
    Details
    Publication Date: 2023-10-28
    Description: Here we demonstrate enhanced natural community APase activity following iron amendment within the low zinc and moderately low iron Western North Atlantic. In contrast we find no evidence for trace metal limitation of APase activity beneath the Saharan dust plume in the Eastern Atlantic. Such intermittent iron limitation of microbial phosphorus acquisition provides an additional facet in the argument for iron controlling the coupling between oceanic nitrogen and phosphorus cycles.
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 2
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    Effect of enhanced pCO2 levels on the production of dissolved organic carbon and transparent exopolymer particles in short-term bioassay experiments (2014)
    PANGAEA
    Details
    Publication Date: 2024-03-15
    Description: It has been proposed that increasing levels of pCO2 in the surface ocean will lead to more partitioning of the organic carbon fixed by marine primary production into the dissolved rather than the particulate fraction. This process may result in enhanced accumulation of dissolved organic carbon (DOC) in the surface ocean and/or concurrent accumulation of transparent exopolymer particles (TEPs), with important implications for the functioning of the marine carbon cycle. We investigated this in shipboard bioassay experiments that considered the effect of four different pCO2 scenarios (ambient, 550, 750 and 1000 µatm) on unamended natural phytoplankton communities from a range of locations in the northwest European shelf seas. The environmental settings, in terms of nutrient availability, phytoplankton community structure and growth conditions, varied considerably between locations. We did not observe any strong or consistent effect of pCO2 on DOC production. There was a significant but highly variable effect of pCO2 on the production of TEPs. In three of the five experiments, variation of TEP production between pCO2 treatments was caused by the effect of pCO2 on phytoplankton growth rather than a direct effect on TEP production. In one of the five experiments, there was evidence of enhanced TEP production at high pCO2 (twice as much production over the 96 h incubation period in the 750 matm treatment compared with the ambient treatment) independent of indirect effects, as hypothesised by previous studies. Our results suggest that the environmental setting of experiments (community structure, nutrient availability and occurrence of phytoplankton growth) is a key factor determining the TEP response to pCO2 perturbations.
    Keywords: Alkalinity, total; Aragonite saturation state; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, organic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyll a; Coast and continental shelf; Coulometric titration; D366_E1; D366_E2; D366_E3; D366_E4; D366_E5; Entire community; Event label; EXP; Experiment; Flag; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Identification; Laboratory experiment; Nitrate; North Atlantic; OA-ICC; Ocean Acidification International Coordination Centre; Open ocean; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Phosphate; Phytoplankton; Potentiometric titration; Salinity; Silicate; Temperate; Temperature, water; Time in hours; Transparent exopolymer particles as Gum Xanthan equivalents per volume; Treatment; UKOA; United Kingdom Ocean Acidification research programme
    Type: Dataset
    Format: text/tab-separated-values, 12066 data points
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    DATA PANGAEA
  • 3
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    Phytoplankton responses and associated carbon cycling during shipboard carbonate chemistry manipulation experiments conducted around Northwest European shelf seas (2014)
    PANGAEA
    Details
    Publication Date: 2024-03-15
    Description: The ongoing oceanic uptake of anthropogenic carbon dioxide (CO2) is significantly altering the carbonate chemistry of seawater, a phenomenon referred to as ocean acidification. Experimental manipulations have been increasingly used to gauge how continued ocean acidification will potentially impact marine ecosystems and their associated biogeochemical cycles in the future; however, results amongst studies, particularly when performed on natural communities, are highly variable, which may reflect community/environment-specific responses or inconsistencies in experimental approach. To investigate the potential for identification of more generic responses and greater experimentally reproducibility, we devised and implemented a series (n = 8) of short-term (2-4 days) multi-level (〉=4 conditions) carbonate chemistry/nutrient manipulation experiments on a range of natural microbial communities sampled in Northwest European shelf seas. Carbonate chemistry manipulations and resulting biological responses were found to be highly reproducible within individual experiments and to a lesser extent between geographically separated experiments. Statistically robust reproducible physiological responses of phytoplankton to increasing pCO2, characterised by a suppression of net growth for small-sized cells (〈10 µm), were observed in the majority of the experiments, irrespective of natural or manipulated nutrient status. Remaining between-experiment variability was potentially linked to initial community structure and/or other site-specific environmental factors. Analysis of carbon cycling within the experiments revealed the expected increased sensitivity of carbonate chemistry to biological processes at higher pCO2 and hence lower buffer capacity. The results thus emphasise how biogeochemical feedbacks may be altered in the future ocean.
    Keywords: Alkalinity, total; Aragonite saturation state; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, organic, particulate; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyll a; Ciliates; Coast and continental shelf; Coccospheres; Community composition and diversity; Coulometric titration; D366_E1; D366_E2; D366_E2b; D366_E3; D366_E4; D366_E4b; D366_E5; D366_E5b; Diatoms; Dinoflagellates; Entire community; Event label; EXP; Experiment; Flag; Flagellates; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Identification; Laboratory experiment; Macro-nutrients; Nanoflagellates, heterotrophic; Nitrate; North Atlantic; OA-ICC; Ocean Acidification International Coordination Centre; Open ocean; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Phosphate; Photosynthetic efficiency; Plankton; Potentiometric titration; Primary production, carbon assimilation (24 hr.); Primary production/Photosynthesis; Salinity; Silicate; Synechococcus; Temperate; Temperature, water; Time in hours; Treatment; UKOA; United Kingdom Ocean Acidification research programme
    Type: Dataset
    Format: text/tab-separated-values, 16897 data points
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    DATA PANGAEA
  • 4
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    Iron limitation of microbial phosphorus acquisition in the tropical North Atlantic (2017)
    Nature Research
    In:  Nature Communications, 8 (15465).
    Details
    Publication Date: 2021-04-23
    Description: In certain regions of the predominantly nitrogen limited ocean, microbes can become co-limited by phosphorus. Within such regions, a proportion of the dissolved organic phosphorus pool can be accessed by microbes employing a variety of alkaline phosphatase (APase) enzymes. In contrast to the PhoA family of APases that utilize zinc as a cofactor, the recent discovery of iron as a cofactor in the more widespread PhoX and PhoD implies the potential for a biochemically dependant interplay between oceanic zinc, iron and phosphorus cycles. Here we demonstrate enhanced natural community APase activity following iron amendment within the low zinc and moderately low iron Western North Atlantic. In contrast we find no evidence for trace metal limitation of APase activity beneath the Saharan dust plume in the Eastern Atlantic. Such intermittent iron limitation of microbial phosphorus acquisition provides an additional facet in the argument for iron controlling the coupling between oceanic nitrogen and phosphorus cycles.
    Type: Article , PeerReviewed
    Format: text
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    PAPER (OCEANREP)
  • 5
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    Environmental controls on the biogeography of diazotrophy and Trichodesmium in the Atlantic Ocean (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 29 (6). pp. 865-884.
    Details
    Publication Date: 2021-04-23
    Description: The cyanobacterium Trichodesmium is responsible for a significant proportion of the annual "new" nitrogen introduced into the global ocean. Despite being arguably the best studied marine diazotroph, the factors controlling the distribution and growth of Trichodesmium remain a subject of debate, with sea surface temperature, the partial pressure of CO2, and nutrients including iron (Fe) and phosphorus (P), all suggested to be important. Synthesizing data from seven cruises collectively spanning large temporal and spatial scales across the Atlantic Ocean, including two previously unreported studies crossing the largely undersampled South Atlantic gyre, we assessed the relationship between proposed environmental drivers and both community N2 fixation rates and the distribution of Trichodesmium. Simple linear regression analysis would suggest no relationship between any of the sampled environmental variables and N2 fixation rates. However, considering the concentrations of iron and phosphorus together within a simplified resource-ratio framework, illustrated using an idealized numerical model, indicates the combined effects these nutrients have on Trichodesmium and broader diazotroph biogeography, alongside the reciprocal maintenance of different biogeographic provinces of the (sub)tropical Atlantic in states of Fe or P oligotrophy by diazotrophy. The qualitative principles of the resource-ratio framework are argued to be consistent with both the previously described North-South Atlantic contrast in Trichodesmium abundance and the presence and consequence of a substantial non-Trichodesmium diazotrophic community in the western South Atlantic subtropical gyre. A comprehensive, observation-based explanation of the interactions between Trichodesmium and the wider diazotrophic community with iron and phosphorus in the Atlantic Ocean is thus revealed.
    Type: Article , PeerReviewed
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  • 6
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    Large-scale distribution of Atlantic nitrogen fixation controlled by iron availability (2009)
    Nature Publishing Group
    In:  Nature Geoscience, 2 . pp. 867-871.
    Details
    Publication Date: 2017-02-22
    Description: Oceanic fixed-nitrogen concentrations are controlled by the balance between nitrogen fixation and denitrification. A number of factors, including iron limitation, can restrict nitrogen fixation, introducing the potential for decoupling of nitrogen inputs and losses. Such decoupling could significantly affect the oceanic fixed-nitrogen inventory and consequently the biological component of ocean carbon storage and hence air–sea partitioning of carbon dioxide. However, the extent to which nutrients limit nitrogen fixation in the global ocean is uncertain. Here, we examined rates of nitrogen fixation and nutrient concentrations in the surface waters of the Atlantic Ocean along a north–south 10,000 km transect during October and November 2005. We show that rates of nitrogen fixation were markedly higher in the North Atlantic compared with the South Atlantic Ocean. Across the two basins, nitrogen fixation was positively correlated with dissolved iron and negatively correlated with dissolved phosphorus concentrations. We conclude that inter-basin differences in nitrogen fixation are controlled by iron supply rather than phosphorus availability. Analysis of the nutrient content of deep waters suggests that the fixed nitrogen enters North Atlantic Deep Water. Our study thus supports the suggestion that iron significantly influences nitrogen fixation5, and that subsequent interactions with ocean circulation patterns contribute to the decoupling of nitrogen fixation and loss.
    Type: Article , PeerReviewed
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  • 7
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    Iron limits primary productivity during spring bloom development in the central North Atlantic (2006)
    Wiley
    In:  Global Change Biology, 12 (4). pp. 623-624.
    Details
    Publication Date: 2018-05-16
    Description: We present in situ biophysical measurements and bioassay experiments that demonstrate iron limitation of primary productivity during the spring bloom in the central North Atlantic. Mass balance calculations indicate that nitrate drawdown is iron (Fe)-limited and that aeolian Fe supply to this region cannot support maximal phytoplankton growth during the bloom. Using a simple simulation model, we show that relief of Fe limitation during the spring bloom can increase nitrate drawdown and, hence, new primary production, by 70%. We conclude that the episodic nature of iron supplied by dust deposition is an important factor controlling the dynamics of the spring bloom. From this, we hypothesize that variability in the timing and magnitude of the spring bloom in response to aeolian Fe supply will affect carbon drawdown and food web dynamics in the central North Atlantic
    Type: Article , PeerReviewed
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  • 8
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    N-Limitation of the Phytoplankton Community in the Mediterranean Sea (2011)
    In:  [Poster] In: ASLO Aquatic Sciences Meeting, 13.-18.02.2011, San Juan, Puerto Rico, USA .
    Details
    Publication Date: 2012-03-15
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 9
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    Seasonal ITCZ migration dynamically controls the location of the (sub)tropical Atlantic biogeochemical divide (2014)
    National Academy of Sciences
    In:  PNAS Proceedings of the National Academy of Sciences of the United States of America, 111 (4). pp. 1438-1442.
    Details
    Publication Date: 2021-04-23
    Description: Inorganic nitrogen depletion restricts productivity in much of the low-latitude oceans, generating a selective advantage for diazotrophic organisms capable of fixing atmospheric dinitrogen (N2). However, the abundance and activity of diazotrophs can in turn be controlled by the availability of other potentially limiting nutrients, including phosphorus (P) and iron (Fe). Here we present high-resolution data (∼0.3°) for dissolved iron, aluminum, and inorganic phosphorus that confirm the existence of a sharp north–south biogeochemical boundary in the surface nutrient concentrations of the (sub)tropical Atlantic Ocean. Combining satellite-based precipitation data with results from a previous study, we here demonstrate that wet deposition in the region of the intertropical convergence zone acts as the major dissolved iron source to surface waters. Moreover, corresponding observations of N2 fixation and the distribution of diazotrophic Trichodesmium spp. indicate that movement in the region of elevated dissolved iron as a result of the seasonal migration of the intertropical convergence zone drives a shift in the latitudinal distribution of diazotrophy and corresponding dissolved inorganic phosphorus depletion. These conclusions are consistent with the results of an idealized numerical model of the system. The boundary between the distinct biogeochemical systems of the (sub)tropical Atlantic thus appears to be defined by the diazotrophic response to spatial–temporal variability in external Fe inputs. Consequently, in addition to demonstrating a unique seasonal cycle forced by atmospheric nutrient inputs, we suggest that the underlying biogeochemical mechanisms would likely characterize the response of oligotrophic systems to altered environmental forcing over longer timescales.
    Type: Article , PeerReviewed
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  • 10
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    Effect of enhanced pCO2 levels on the production of dissolved organic carbon and transparent exopolymer particles in short-term bioassay experiments (2014)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 11 (13). pp. 3695-3706.
    Details
    Publication Date: 2021-04-23
    Description: It has been proposed that increasing levels of pCO(2) in the surface ocean will lead to more partitioning of the organic carbon fixed by marine primary production into the dissolved rather than the particulate fraction. This process may result in enhanced accumulation of dissolved organic carbon (DOC) in the surface ocean and/or concurrent accumulation of transparent exopolymer particles (TEPs), with important implications for the functioning of the marine carbon cycle. We investigated this in shipboard bioassay experiments that considered the effect of four different pCO(2) scenarios (ambient, 550, 750 and 1000 mu atm) on unamended natural phytoplankton communities from a range of locations in the northwest European shelf seas. The environmental settings, in terms of nutrient availability, phytoplankton community structure and growth conditions, varied considerably between locations. We did not observe any strong or consistent effect of pCO(2) on DOC production. There was a significant but highly variable effect of pCO(2) on the production of TEPs. In three of the five experiments, variation of TEP production between pCO(2) treatments was caused by the effect of pCO(2) on phytoplankton growth rather than a direct effect on TEP production. In one of the five experiments, there was evidence of enhanced TEP production at high pCO(2) (twice as much production over the 96 h incubation period in the 750 mu atm treatment compared with the ambient treatment) independent of indirect effects, as hypothesised by previous studies. Our results suggest that the environmental setting of experiments (community structure, nutrient availability and occurrence of phytoplankton growth) is a key factor determining the TEP response to pCO(2) perturbations.
    Type: Article , PeerReviewed
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