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  • PANGAEA  (86)
  • Frontiers  (3)
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  • 1
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    Phytoplankton Blooms at Increasing Levels of Atmospheric Carbon Dioxide: Experimental Evidence for Negative Effects on Prymnesiophytes and Positive on Small Picoeukaryotes (2017)
    Frontiers
    In:  Frontiers in Marine Science, 4 . Art.Nr. 64.
    Details
    Publication Date: 2020-02-06
    Description: Anthropogenic emissions of carbon dioxide (CO2) and the ongoing accumulation in the surface ocean together with concomitantly decreasing pH and calcium carbonate saturation states have the potential to impact phytoplankton community composition and therefore biogeochemical element cycling on a global scale. Here we report on a recent mesocosm CO2 perturbation study (Raunefjorden, Norway), with a focus on organic matter and phytoplankton dynamics. Cell numbers of three phytoplankton groups were particularly affected by increasing levels of seawater CO2 throughout the entire experiment, with the cyanobacterium Synechococcus and picoeukaryotes (prasinophytes) profiting, and the coccolithophore Emiliania huxleyi (prymnesiophyte) being negatively impacted. Combining these results with other phytoplankton community CO2 experiments into a data-set of global coverage suggests that, whenever CO2 effects are found, prymnesiophyte (especially coccolithophore) abundances are negatively affected, while the opposite holds true for small picoeukaryotes belonging to the class of prasinophytes, or the division of chlorophytes in general. Future reductions in calcium carbonate-producing coccolithophores, providing ballast which accelerates the sinking of particulate organic matter, together with increases in picoeukaryotes, an important component of the microbial loop in the euphotic zone, have the potential to impact marine export production, with feedbacks to Earth's climate system.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.3389/fmars.2017.00064
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Response of plankton community respiration under variable simulated upwelling events (2022)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Climate change is expected to alter the intensity and frequency of upwelling in high productive coastal regions, thus impacting nutrient fluxes, primary productivity and consequently carbon cycling. However, it is unknown how these changes will impact the planktonic (phytoplankton and bacteria) community structure, which affects community respiration (CR) and hence the carbon available for sequestration or transfer to upper trophic levels. Here we present results from a 37-day mesocosm experiment where we examined the response of CR to nutrient additions by simulating upwelling events at different intensities (low, medium, high and extreme) and modes (singular and recurring additions). We also analysed the potential contribution of different plankton size classes and functional groups to CR. The trend in accumulated CR with respect to nutrient fertilisation (total nitrogen added during the experiment) was linear in the two modes. Microplankton (mostly diatoms) and nanoplankton (small flagellates) dominated under extreme upwelling intensities and high CR in both singular and recurring upwelling modes, explaining 〉65% of the observed variability in CR. In contrast, prokaryotic picoplankton (heterotrophic bacteria and autotrophic cyanobacteria) explained 〈43% of the variance in CR under the rest of the upwelling intensities and modes tested. Changes in planktonic community structure, while modulating CR variability, would regulate the metabolic balance of the ecosystem, shifting it towards net-heterotrophy when the community is dominated by small heterotrophs and to net-autotrophy when large autotrophs prevail; although depending on the mode in which nutrients are supplied to the system. This shift in the dominance of planktonic organism will hence affect not only CR but also carbon sequestration in upwelling regions
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Microzooplankton communities and their grazing of phytoplankton under artificial upwelling in the oligotrophic ocean (2023)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Ocean artificial upwelling has been suggested to boost primary production and increase harvestable resources such as fish. Yet, for this ecosystem-based approach to work, an effective energy transfer up the food web is required. Here, we studied the trophic role of microzooplankton under artificial upwelling via biomass and community composition as well as grazing rates on phytoplankton. Using mesocosms in the oligotrophic ocean, we supplied nutrient-rich deep water at varying intensities (low to high) and addition modes (a Singular large pulse or smaller Recurring pulses). Deep-water fertilization created a diatom-dominated bloom that scaled with the amount of inorganic nutrients added, but also Synechococcus -like cells, picoeukaryotes and nanophytoplankton increased in abundance with added nutrients. After 30 days, towards the end of the experiment, coccolithophores bloomed under recurring upwelling of high intensity. Across all upwelling scenarios, the microzooplankton community was dominated by ciliates, dinoflagellates (mixo- and heterotrophic) and radiolarians. Under the highest upwelling intensity, the average grazing rates of Synechococcus -like cells, picoeukaryotes and nanophytoplankton by microzooplankton were 0.35 d -1 ± 0.18 (SD), 0.09 d -1 ± 0.12 (SD), and 0.11 d -1 ± 0.13 (SD), respectively. There was little temporal variation in grazing of nanophytoplankton but grazing of Synechococcus -like cells and picoeukaryotes were more variable. There were positive correlations between abundance of these groups and grazing rates, suggesting a response in the microzooplankton community to prey availability. The average phytoplankton to microzooplankton ratio (biovolume) increased with added deep water, and this increase was highest in the Singular treatment, reaching ~30 (m 3 m -3 ), whereas the phytoplankton to total zooplankton biomass ratio (weight) increased from ~1 under low upwelling to ~6 (g g -1 ) in the highest upwelling but without a difference between the Singular and the Recurring mode. Several smaller, recurring upwelling events increased the importance of microzooplankton compared with one large pulse of deep water. Our results demonstrate that microzooplankton would be an important component for trophic transfer if artificial upwelling would be carried out at scale in the oligotrophic ocean.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: other
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Upwelling amplifies ocean acidification on the East Australian shelf: implications for marine ecosystems -Measurements from 2017-08-17 to 2017-10-19 (2019)
    PANGAEA
    Details
    Publication Date: 2023-03-14
    Keywords: Alkalinity, total; Aragonite saturation state; Calculated; Calculated based on salinity (Jiang et al. 2014); Calculated using CO2SYS; Cape_Byron; Carbon, inorganic, dissolved; DATE/TIME; Day of the year; DEPTH, water; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); MULT; Multiple investigations; New South Wales, Australia; Ocean acidification; Omega; Oxygen; Oxygen saturation; pH; pH, standard deviation; Pressure, water; Salinity; SeaPHOX; SeapHOx, MicroCAT; Temperature, water; thresholds; Upwelling; western boundary system
    Type: Dataset
    Format: text/tab-separated-values, 84790 data points
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    DATA PANGAEA
  • 5
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    Upwelling amplifies ocean acidification on the East Australian shelf: implications for marine ecosystems - Measurements from 2017-11-02 to 2018-01-07 (2019)
    PANGAEA
    Details
    Publication Date: 2023-03-14
    Keywords: Alkalinity, total; Aragonite saturation state; Calculated; Calculated based on salinity (Jiang et al. 2014); Calculated using CO2SYS; Cape_Byron; Carbon, inorganic, dissolved; DATE/TIME; Day of the year; DEPTH, water; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); MULT; Multiple investigations; New South Wales, Australia; Ocean acidification; Omega; Oxygen; Oxygen saturation; pH; pH, standard deviation; Pressure, water; Salinity; SeaPHOX; SeapHOx, MicroCAT; Temperature, water; thresholds; Upwelling; western boundary system
    Type: Dataset
    Format: text/tab-separated-values, 88634 data points
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    DATA PANGAEA
  • 6
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    Bacteria growth, enzyme activities and TEP during KOSMOS 2011 mesocosm experiment in the Raunefjord (2016)
    PANGAEA
    In:  Supplement to: Endres, Sonja; Galgani, Luisa; Riebesell, Ulf; Schulz, Kai Georg; Engel, Anja (2014): Stimulated Bacterial Growth under Elevated pCO2: Results from an Off-Shore Mesocosm Study. PLoS ONE, 9(6), e99228, https://doi.org/10.1371/journal.pone.0099228
    Details
    Publication Date: 2023-03-14
    Description: Marine bacteria are the main consumers of freshly produced organic matter. Many enzymatic processes involved in the bacterial digestion of organic compounds were shown to be pH sensitive in previous studies. Due to the continuous rise in atmospheric CO2 concentration, seawater pH is presently decreasing at a rate unprecedented during the last 300 million years but the consequences for microbial physiology, organic matter cycling and marine biogeochemistry are still unresolved. We studied the effects of elevated seawater pCO2 on a natural plankton community during a large-scale mesocosm study in a Norwegian fjord. Nine Kiel Off-Shore Mesocosms for Future Ocean Simulations (KOSMOS) were adjusted to different pCO2 levels ranging initially from ca. 280 to 3000 µatm and sampled every second day for 34 days. The first phytoplankton bloom developed around day 5. On day 14, inorganic nutrients were added to the enclosed, nutrient-poor waters to stimulate a second phytoplankton bloom, which occurred around day 20. Our results indicate that marine bacteria benefit directly and indirectly from decreasing seawater pH. During the first phytoplankton bloom, 5-10% more transparent exopolymer particles were formed in the high pCO2 mesocosms. Simultaneously, the efficiency of the protein-degrading enzyme leucine aminopeptidase increased with decreasing pH resulting in up to three times higher values in the highest pCO2/lowest pH mesocosm compared to the controls. In general, total and cell-specific aminopeptidase activities were elevated under low pH conditions. The combination of enhanced enzymatic hydrolysis of organic matter and increased availability of gel particles as substrate supported up to 28% higher bacterial abundance in the high pCO2 treatments. We conclude that ocean acidification has the potential to stimulate the bacterial community and facilitate the microbial recycling of freshly produced organic matter, thus strengthening the role of the microbial loop in the surface ocean.
    Keywords: Abundance per volume; BIOACID; Biological Impacts of Ocean Acidification; Chlorophyll a; DATE/TIME; Day of experiment; KOSMOS_2011_Bergen; Leucine aminopeptidase activity; MESO; Mesocosm experiment; pH; Raunefjord; Sample code/label; Transparent exopolymer particles as Gum Xanthan equivalents per volume; Transparent exopolymer particles as Gum Xanthan equivalents per volume, std dev
    Type: Dataset
    Format: text/tab-separated-values, 2053 data points
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    DATA PANGAEA
  • 7
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    Gross primary production, respiration, and net calcification in coral reef sediments of Heron Island Lagoon, Australia, determined by in situ benthic chamber incubations (2017)
    PANGAEA
    In:  Supplement to: Lantz, Coulson A; Schulz, Kai Georg; Stoltenberg, Laura; Eyre, Bradley D (2017): The short-term combined effects of temperature and organic matter enrichment on permeable coral reef carbonate sediment metabolism and dissolution. Biogeosciences, 14(23), 5377-5391, https://doi.org/10.5194/bg-14-5377-2017
    Details
    Publication Date: 2023-03-14
    Description: Rates of gross primary production (GPP), respiration (R), and net calcification (Gnet) in coral reef sediments are expected to change in response to global warming (and the consequent increase in sea surface temperature) and coastal eutrophication (and the subsequent increase in the concentration of organic matter (OM) being filtered by permeable coral reef carbonate sediments). To date, no studies have examined the combined effect of seawater warming and OM enrichment on coral reef carbonate sediment metabolism and dissolution. This study used 22-hour in situ benthic chamber incubations to examine the combined effect of temperature (T) and OM, in the form of coral mucus and phytodetritus, on GPP, R, and Gnet in the permeable coral reef carbonate sediments of Heron Island lagoon, Australia. Compared to control incubations, both warming (+2.4 ºC) and OM increased R and GPP. Under warmed conditions, R was enhanced to a greater extent than GPP, resulting in a shift to net heterotrophy and net dissolution. Under both phytodetritus and coral mucus treatments, GPP was enhanced to a greater extent than R, resulting in a net increase in GPP/R and Gnet. The combined effect of warming and OM enhanced R and GPP, but the net effect on GPP/R and Gnet was not significantly different from control incubations. These findings show that a shift to net heterotrophy and dissolution due to short-term increases in seawater warming may be countered by a net increase GPP/R and Gnet due to short-term increases in nutrient release from OM.
    Keywords: Alkalinity, total; Aragonite saturation state; Australia; Calcification rate of calcium carbonate; Carbon, inorganic, dissolved; DATE/TIME; Gross primary production/Respiration rate ratio; Gross primary production of oxygen; Heron_Island_lagoon; Incubation duration; Net calcification rate of calcium carbonate; Net primary production of oxygen; Oxygen; pH; Respiration rate, oxygen; Time in hours; Treatment
    Type: Dataset
    Format: text/tab-separated-values, 1344 data points
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    DATA PANGAEA
  • 8
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    Ocean Acidification and Organic Matter Enrichment Alter Carbonate Sediment Metabolism Through Different Pathways
    PANGAEA
    In:  Supplement to: Lantz, Coulson A; Schulz, Kai Georg; Eyre, Bradley D (in review): Ocean Acidification and Organic Matter Enrichment Alter Carbonate Sediment Metabolism Through Different Pathways. Journal of Geophysical Research: Oceans
    Details
    Publication Date: 2023-05-12
    Description: Ocean acidification (OA) and organic matter enrichment (due to coastal eutrophication) could act in concert to shift coral reef carbonate sediments from a present state of net calcification to a future state of net dissolution, but no studies have examined the combined effect of these stressors on sediment metabolism and dissolution. This study used 22-hour incubations in flume aquaria with captive sediment communities to measure the combined effect of OA and organic matter (OM) enrichment, on coral reef sediment gross primary productivity (GPP), respiration (R), and net calcification (Gnet). Relative to control sediment communities, both OA ( 1000 µatm) and OM enrichment (+ 40 µmol C/L) significantly decreased rates of sediment Gnet by 98% and 15% mmol CaCO3/m**2/h, respectively , but the mechanism behind this decrease differed. The OA-mediated transition to net dissolution was geochemical, as rates of GPP and R remained unaffected and dissolution was solely enhanced by a decline in the aragonite saturation state (Omega arg) of the overlying water column. In contrast, the OM-mediated decline in Gnet was due to a decline in GPP/R, thereby biologically reducing overlying seawater Ωarg due to the increased respiratory addition of CO2. The decrease in Gnet in response to a combination of both stressors was additive (- 10% relative to OA alone) but this decrease did not significantly differ from the effect of OA alone. In this study OA was the primary driver of future carbonate sediment dissolution, but longer-term experiments with chronic organic matter enrichment are required.
    Keywords: Benthos; Calcification/Dissolution; Coast and continental shelf; Containers and aquaria (20-1000 L or 〈 1 m**2); Entire community; Laboratory experiment; OA-ICC; Ocean Acidification International Coordination Centre; Other; Primary production/Photosynthesis; Respiration; Soft-bottom community; South Pacific; Temperate
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 9
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    OA and ripples metabolism data (2020)
    PANGAEA
    Details
    Publication Date: 2023-01-13
    Keywords: DATE/TIME; Gross primary production/Respiration rate ratio; Gross primary production of oxygen; Identification; Net calcification rate of calcium carbonate; Net community calcification rate of calcium carbonate, dark; Net community calcification rate of calcium carbonate, light; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Respiration rate, oxygen; Treatment
    Type: Dataset
    Format: text/tab-separated-values, 216 data points
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    DATA PANGAEA
  • 10
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    Sediment topography enhances the response of coral reef carbonate sediment dissolution to ocean acidification (2020)
    PANGAEA
    Details
    Publication Date: 2023-01-13
    Description: The interaction between current flow and topography (e.g., surface ripples) in shallow, permeable coral reef carbonate sediments establishes pressure gradients that increase the rate of sediment-water solute exchange relative to fluid shear along a flat bottom. It is currently unknown how this effect from surface ripples will modify the rate at which the sediment porewater is exposed to future chemical changes in the overlying water column, such as elevated pCO2 that is causing ocean acidification (OA). To address this question, this study used a series of 22-hour incubations in flume aquaria with permeable calcium carbonate sediment communities and examined the interactive effect of pCO2 (400 and 1000 µatm) and surface topography (flat and rippled sediments) on carbonate sediment metabolism and dissolution. According to dissolved oxygen optode image analysis, the presence of surface ripples increased the oxygenated area below the sediment surface by 295% relative to flat sediments. This was reflected in the sediment-to-water column fluxes of dissolved oxygen, where rippled sediments exhibited rates of respiration (R) and gross primary production (GPP) that were ~ 45% and ~ 50% higher, respectively, than flat sediments. An increase in pCO2 shifted the sediments in the flat flumes from net calcifying (Gnet 〉 0) to net dissolving (Gnet 〈 0), an effect that was amplified an additional ~ 60% in rippled sediments. These results suggest that current estimates of coral reef carbonate sediment Gnet may be underestimating the dissolution response to OA where the carbonate sediment environment exhibits ripples in the topography.
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
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