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  • 1
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    Ocean acidification and marine trace gas emissions (2009)
    National Academy of Sciences
    Details
    Publication Date: 2009-12-22
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 2
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    Two intertidal, non-calcifying macroalgae (Palmaria palmata and Saccharina latissima) show complex and variable responses to short-term CO2 acidification (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-27
    Description: Ocean acidification, the result of increased dissolution of carbon dioxide (CO 2 ) in seawater, is a leading subject of current research. The effects of acidification on non-calcifying macroalgae are, however, still unclear. The current study reports two 1-month studies using two different macroalgae, the red alga Palmaria palmata (Rhodophyta) and the kelp Saccharina latissima (Phaeophyta), exposed to control (pH NBS = ~8.04) and increased (pH NBS = ~7.82) levels of CO 2 -induced seawater acidification. The impacts of both increased acidification and time of exposure on net primary production (NPP), respiration ( R ), dimethylsulphoniopropionate (DMSP) concentrations, and algal growth have been assessed. In P. palmata , although NPP significantly increased during the testing period, it significantly decreased with acidification, whereas R showed a significant decrease with acidification only. S. latissima significantly increased NPP with acidification but not with time, and significantly increased R with both acidification and time, suggesting a concomitant increase in gross primary production. The DMSP concentrations of both species remained unchanged by either acidification or through time during the experimental period. In contrast, algal growth differed markedly between the two experiments, in that P. palmata showed very little growth throughout the experiment, while S. latissima showed substantial growth during the course of the study, with the latter showing a significant difference between the acidified and control treatments. These two experiments suggest that the study species used here were resistant to a short-term exposure to ocean acidification, with some of the differences seen between species possibly linked to different nutrient concentrations between the experiments.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 3
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    Contrasting responses of DMS and DMSP to ocean acidification in Arctic waters (2012)
    Copernicus
    Details
    Publication Date: 2012-09-18
    Description: Increasing atmospheric CO2 is decreasing ocean pH most rapidly in colder regions such as the Arctic. As a component of the EPOCA pelagic mesocosm experiment off Spitzbergen in 2010, we examined the consequences of decreased pH and increased pCO2 on the concentrations of dimethylsulphide (DMS). DMS is an important reactant and contributor to aerosol formation and growth in the Arctic troposphere. In the nine mesocosms with initial pH 8.3 to 7.5, equivalent to pCO2 of 180 to 1420 μatm, highly significant but inverse responses to acidity (hydrogen ion concentration [H+]) occurred following nutrient addition. Compared to ambient [H+], average concentrations of DMS during the most representative phase of the 30 d experiment were reduced by approximately 60% at the highest [H+] and by 35% at [H+] equivalent to 750 μatm pCO2, as predicted for 2100. In contrast, concentrations of dimethylsulphoniopropionate (DMSP), the precursor of DMS, were elevated by approximately 50% at the highest [H+] and by 30% at [H+] corresponding to 750 μatm pCO2. Measurements of the specific rate of synthesis of DMSP by phytoplankton indicate increased production at high [H+], in parallel to rates of inorganic carbon fixation. The elevated DMSP production at high [H+] was largely a consequence of increased dinoflagellate biomass and in particular, the increased abundance of the species Heterocapsa rotundata. We discuss both phytoplankton and bacterial processes that may explain the reduced ratios of DMS:DMSPt at higher [H+]. The experimental design of eight treatment levels provides comparatively robust empirical relationships of DMS and DMSP concentration, DMSP production and dinoflagellate biomass versus [H+] in Arctic waters.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 4
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    Response of halocarbons to ocean acidification in the Arctic (2012)
    Copernicus
    Details
    Publication Date: 2012-07-09
    Description: The potential effect of ocean acidification (OA) on seawater halocarbons in the Arctic was investigated during a mesocosm experiment in Spitsbergen in June–July 2010. Over a period of 5 weeks, natural phytoplankton communities in nine ~50 m3 mesocosms were studied under a range of pCO2 treatments from ~185 μatm to ~1420 μatm. In general, the response of halocarbons to pCO2 was subtle, or undetectable. A large number of significant correlations with a range of biological parameters (chlorophyll a, microbial plankton community, phytoplankton pigments) were identified, indicating a biological control on the concentrations of halocarbons within the mesocosms. The temporal dynamics of iodomethane (CH3I) alluded to active turnover of this halocarbon in the mesocosms and strong significant correlations with biological parameters suggested a biological source. However, despite a pCO2 effect on various components of the plankton community, and a strong association between CH3I and biological parameters, no effect of pCO2 was seen in CH3I. Diiodomethane (CH2I2) displayed a number of strong relationships with biological parameters. Furthermore, the concentrations, the rate of net production and the sea-to-air flux of CH2I2 showed a significant positive response to pCO2. There was no clear effect of pCO2 on bromocarbon concentrations or dynamics. However, periods of significant net loss of bromoform (CHBr3) were found to be concentration-dependent, and closely correlated with total bacteria, suggesting a degree of biological consumption of this halocarbon in Arctic waters. Although the effects of OA on halocarbon concentrations were marginal, this study provides invaluable information on the production and cycling of halocarbons in a region of the world's oceans likely to experience rapid environmental change in the coming decades.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 5
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    Consistent increase in dimethyl sulphide (DMS) in response to high CO2 in five shipboard bioassays from contrasting NW European waters (2014)
    Copernicus
    Details
    Publication Date: 2014-02-10
    Description: The ubiquitous marine trace gas dimethyl sulphide (DMS) comprises the greatest natural source of sulphur to the atmosphere and is a key player in atmospheric chemistry and climate. We explore the short term response of DMS and its algal precursor dimethyl sulphoniopropionate (DMSP) production and cycling to elevated carbon dioxide (CO2) and ocean acidification (OA) in five highly replicated 96 h shipboard bioassay experiments from contrasting sites in NW European shelf waters. In general, the response to OA throughout this region showed little variation, despite encompassing a range of biological and biogeochemical conditions. We observed consistent and marked increases in DMS concentrations relative to ambient controls, and decreases in DMSP concentrations. Quantification of rates of specific DMSP synthesis by phytoplankton and bacterial DMS gross production/consumption suggest algal processes dominated the CO2 response, likely due to a physiological response manifested as increases in direct cellular exudation of DMS and/or DMSP lyase enzyme activities. The variables and rates we report increase our understanding of the processes behind the response to OA. This could provide the opportunity to improve upon mesocosm-derived empirical modelling relationships, and move towards a mechanistic approach for predicting future DMS concentrations.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 6
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    Results from the first national UK inter-laboratory calibration for very short-lived halocarbons (2011)
    Copernicus
    Details
    Publication Date: 2011-01-28
    Description: Very short-lived halocarbons (VSLH) such as CH3I, CH2Br2 and CHBr3 provide an important source of reactive halogens to the atmosphere, however high spatial and seasonal variability in their ambient mixing ratios and sea-air fluxes gives rise to considerable uncertainty in global scale emission estimates. One solution to improve global flux estimates is to combine the multitude of individually published datasets to produce a database of collated global halocarbon observations. Some progress towards this has already been achieved through the HalOcAt (Halocarbons in the Ocean and Atmosphere) database initiative, however the absence of a common calibration scale for very short-lived halocarbons makes it difficult to distinguish true environmental variations from artefacts arising from differences between calibration methodologies. As such, the lack of inter-calibrations for both air and seawater measurements of very short-lived halocarbons has been identified as a major limitation to current estimations of the global scale impact of these reactive trace gases. Here we present the key findings from the first national UK inter-laboratory comparison for calibrations of the halocarbons CH3I, CH2Br2 and CHBr3. The aim of this inter-calibration was to provide transparency between halocarbon calibrations from major UK research institutions, an important step towards enabling all measurements from these institutions to be treated as one coherent integrated dataset for global source term parameterisations.
    Electronic ISSN: 1867-8610
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
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    Air-Sea Fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the South West Coast of the UK (2016)
    Copernicus
    Details
    Publication Date: 2016-01-18
    Description: We present air-sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the South West coast of the United Kingdom. Measurements from the southwest direction (background marine air) at three different sampling heights (approximately 15, 18, 27 m above mean sea level, AMSL) in three different periods during 2014–2015 are shown. At sampling heights ≥ 18 m AMSL, measured fluxes of momentum and sensible heat demonstrate reasonable agreement with their expected transfer rates over the open ocean. This confirms the suitability of PPAO for air-sea exchange measurements. We observed reductions in the air-to-sea fluxes of CO2 from spring to summer in both years, which coincided with the breakdown of the spring phytoplankton bloom. At all sampling heights, mean CH4 fluxes were positive, suggesting marine emissions. Higher CH4 fluxes were observed during rising tides (20±3; 29±6; 38±3 μmole m−2 d−1 at 15, 27, 18 m AMSL) than during falling tides (14±2; 21±5; 22±2 μmole m−2 d−1, respectively), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. Based on observations at PPAO, we also estimate the detection limit of the eddy covariance CH4 flux measurement to be ~20 μmole m−2 d−1 over hourly timescales (~4 μmole m−2 d−1 over 24 hours).
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
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    Response of halocarbons to ocean acidification in the Arctic (2013)
    Copernicus
    Details
    Publication Date: 2013-04-08
    Description: The potential effect of ocean acidification (OA) on seawater halocarbons in the Arctic was investigated during a mesocosm experiment in Spitsbergen in June–July 2010. Over a period of 5 weeks, natural phytoplankton communities in nine ~ 50 m3 mesocosms were studied under a range of pCO2 treatments from ~ 185 μatm to ~ 1420 μatm. In general, the response of halocarbons to pCO2 was subtle, or undetectable. A large number of significant correlations with a range of biological parameters (chlorophyll a, microbial plankton community, phytoplankton pigments) were identified, indicating a biological control on the concentrations of halocarbons within the mesocosms. The temporal dynamics of iodomethane (CH3I) alluded to active turnover of this halocarbon in the mesocosms and strong significant correlations with biological parameters suggested a biological source. However, despite a pCO2 effect on various components of the plankton community, and a strong association between CH3I and biological parameters, no effect of pCO2 was seen in CH3I. Diiodomethane (CH2I2) displayed a number of strong relationships with biological parameters. Furthermore, the concentrations, the rate of net production and the sea-to-air flux of CH2I2 showed a significant positive response to pCO2. There was no clear effect of pCO2 on bromocarbon concentrations or dynamics. However, periods of significant net loss of bromoform (CHBr3) were found to be concentration-dependent, and closely correlated with total bacteria, suggesting a degree of biological consumption of this halocarbon in Arctic waters. Although the effects of OA on halocarbon concentrations were marginal, this study provides invaluable information on the production and cycling of halocarbons in a region of the world's oceans likely to experience rapid environmental change in the coming decades.
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
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    Consistent increase in dimethyl sulfide (DMS) in response to high CO2 in five shipboard bioassays from contrasting NW European waters (2014)
    Copernicus
    Details
    Publication Date: 2014-09-16
    Description: The ubiquitous marine trace gas dimethyl sulfide (DMS) comprises the greatest natural source of sulfur to the atmosphere and is a key player in atmospheric chemistry and climate. We explore the short-term response of DMS production and cycling and that of its algal precursor dimethyl sulfoniopropionate (DMSP) to elevated carbon dioxide (CO2) and ocean acidification (OA) in five 96 h shipboard bioassay experiments. Experiments were performed in June and July 2011, using water collected from contrasting sites in NW European waters (Outer Hebrides, Irish Sea, Bay of Biscay, North Sea). Concentrations of DMS and DMSP, alongside rates of DMSP synthesis and DMS production and consumption, were determined during all experiments for ambient CO2 and three high-CO2 treatments (550, 750, 1000 μatm). In general, the response to OA throughout this region showed little variation, despite encompassing a range of biological and biogeochemical conditions. We observed consistent and marked increases in DMS concentrations relative to ambient controls (110% (28–223%) at 550 μatm, 153% (56–295%) at 750 μatm and 225% (79–413%) at 1000 μatm), and decreases in DMSP concentrations (28% (18–40%) at 550 μatm, 44% (18–64%) at 750 μatm and 52% (24–72%) at 1000 μatm). Significant decreases in DMSP synthesis rate constants (μDMSP, d−1) and DMSP production rates (nmol d−1) were observed in two experiments (7–90% decrease), whilst the response under high CO2 from the remaining experiments was generally indistinguishable from ambient controls. Rates of bacterial DMS gross consumption and production gave weak and inconsistent responses to high CO2. The variables and rates we report increase our understanding of the processes behind the response to OA. This could provide the opportunity to improve upon mesocosm-derived empirical modelling relationships and to move towards a mechanistic approach for predicting future DMS concentrations.
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Contrasting responses of DMS and DMSP to ocean acidification in Arctic waters (2013)
    Copernicus
    Details
    Publication Date: 2013-03-20
    Description: Increasing atmospheric CO2 is decreasing ocean pH most rapidly in colder regions such as the Arctic. As a component of the EPOCA (European Project on Ocean Acidification) pelagic mesocosm experiment off Spitzbergen in 2010, we examined the consequences of decreased pH and increased pCO2 on the concentrations of dimethylsulphide (DMS). DMS is an important reactant and contributor to aerosol formation and growth in the Arctic troposphere. In the nine mesocosms with initial pHT 8.3 to 7.5, equivalent to pCO2 of 180 to 1420 μatm, highly significant but inverse responses to acidity (hydrogen ion concentration [H+]) occurred following nutrient addition. Compared to ambient [H+], average concentrations of DMS during the mid-phase of the 30 d experiment, when the influence of altered acidity was unambiguous, were reduced by approximately 60% at the highest [H+] and by 35% at [H+] equivalent to 750 μatm pCO2, as projected for 2100. In contrast, concentrations of dimethylsulphoniopropionate (DMSP), the precursor of DMS, were elevated by approximately 50% at the highest [H+] and by 30% at [H+] corresponding to 750 μatm pCO2. Measurements of the specific rate of synthesis of DMSP by phytoplankton indicate increased production at high [H+], in parallel to rates of inorganic carbon fixation. The elevated DMSP production at high [H+] was largely a consequence of increased dinoflagellate biomass and in particular, the increased abundance of the species Heterocapsa rotundata. We discuss both phytoplankton and bacterial processes that may explain the reduced ratios of DMS:DMSPt (total dimethylsulphoniopropionate) at higher [H+]. The experimental design of eight treatment levels provides comparatively robust empirical relationships of DMS and DMSP concentration, DMSP production and dinoflagellate biomass versus [H+] in Arctic waters.
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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