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  • 1
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    The influence of dissolved inorganic macronutrient concentration and ratio on the elemental stoichiometry of sinking particulate matter and carbon export in the Peruvian upwelling system (2017)
    In:  (Master thesis), Universidade do Algarve, Faro, Portugal, 50 pp
    Details
    Publication Date: 2018-01-05
    Type: Thesis , NonPeerReviewed
    Location Call Number Limitation Availability
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    OceanRep: Thesis - not published by a publisher
  • 2
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    Factors controlling plankton community production, export flux, and particulate matter stoichiometry in the coastal upwelling system off Peru (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-08
    Description: Eastern boundary upwelling systems (EBUS) are among the most productive marine ecosystems on Earth. The production of organic material is fueled by upwelling of nutrient-rich deep waters and high incident light at the sea surface. However, biotic and abiotic factors can modify surface production and related biogeochemical processes. Determining these factors is important because EBUS are considered hotspots of climate change, and reliable predictions of their future functioning requires understanding of the mechanisms driving the biogeochemical cycles therein. In this field experiment, we used in situ mesocosms as tools to improve our mechanistic understanding of processes controlling organic matter cycling in the coastal Peruvian upwelling system. Eight mesocosms, each with a volume of ∼55 m3, were deployed for 50 d ∼6 km off Callao (12∘ S) during austral summer 2017, coinciding with a coastal El Niño phase. After mesocosm deployment, we collected subsurface waters at two different locations in the regional oxygen minimum zone (OMZ) and injected these into four mesocosms (mixing ratio ≈1.5 : 1 mesocosm: OMZ water). The focus of this paper is on temporal developments of organic matter production, export, and stoichiometry in the individual mesocosms. The mesocosm phytoplankton communities were initially dominated by diatoms but shifted towards a pronounced dominance of the mixotrophic dinoflagellate (Akashiwo sanguinea) when inorganic nitrogen was exhausted in surface layers. The community shift coincided with a short-term increase in production during the A. sanguinea bloom, which left a pronounced imprint on organic matter C : N : P stoichiometry. However, C, N, and P export fluxes did not increase because A. sanguinea persisted in the water column and did not sink out during the experiment. Accordingly, export fluxes during the study were decoupled from surface production and sustained by the remaining plankton community. Overall, biogeochemical pools and fluxes were surprisingly constant for most of the experiment. We explain this constancy by light limitation through self-shading by phytoplankton and by inorganic nitrogen limitation which constrained phytoplankton growth. Thus, gain and loss processes remained balanced and there were few opportunities for blooms, which represents an event where the system becomes unbalanced. Overall, our mesocosm study revealed some key links between ecological and biogeochemical processes for one of the most economically important regions in the oceans.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Nitrogen loss processes in response to upwelling in a Peruvian coastal setting dominated by denitrification – a mesocosm approach (2021)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-02-07
    Description: Upwelling of nutrient-rich deep waters make eastern boundary upwelling systems (EBUSs), such as the Humboldt Current system, hot spots of marine productivity. Associated settling of organic matter to depth and consecutive aerobic decomposition results in large subsurface water volumes being oxygen depleted. Under these circumstances, organic matter remineralisation can continue via denitrification, which represents a major loss pathway for bioavailable nitrogen. Additionally, anaerobic ammonium oxidation can remove significant amounts of nitrogen in these areas. Here we assess the interplay of suboxic water upwelling and nitrogen cycling in a manipulative offshore mesocosm experiment. Measured denitrification rates in incubations with water from the oxygen-depleted bottom layer of the mesocosms (via 15N label incubations) mostly ranged between 5.5 and 20 nmol N2 L−1 h−1 (interquartile range), reaching up to 80 nmol N2 L−1 h−1. However, actual in situ rates in the mesocosms, estimated via Michaelis–Menten kinetic scaling, did most likely not exceed 0.2–4.2 nmol N2 L−1 h−1 (interquartile range) due to substrate limitation. In the surrounding Pacific, measured denitrification rates were similar, although indications of substrate limitation were detected only once. In contrast, anammox (anaerobic ammonium oxidation) made only a minor contribution to the overall nitrogen loss when encountered in both the mesocosms and the Pacific Ocean. This was potentially related to organic matter C / N stoichiometry and/or process-specific oxygen and hydrogen sulfide sensitivities. Over the first 38 d of the experiment, total nitrogen loss calculated from in situ rates of denitrification and anammox was comparable to estimates from a full nitrogen budget in the mesocosms and ranged between ∼ 1 and 5.5 µmol N L−1. This represents up to ∼  20 % of the initially bioavailable inorganic and organic nitrogen standing stocks. Interestingly, this loss is comparable to the total amount of particulate organic nitrogen that was exported into the sediment traps at the bottom of the mesocosms at about 20 m depth. Altogether, this suggests that a significant portion, if not the majority of nitrogen that could be exported to depth, is already lost, i.e. converted to N2 in a relatively shallow layer of the surface ocean, provided that there are oxygen-deficient conditions like those during coastal upwelling in our study. Published data for primary productivity and nitrogen loss in all EBUSs reinforce such conclusion.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Extreme Levels of Ocean Acidification Restructure the Plankton Community and Biogeochemistry of a Temperate Coastal Ecosystem: A Mesocosm Study (2021)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: The oceans’ uptake of anthropogenic carbon dioxide (CO2) decreases seawater pH and alters the inorganic carbon speciation – summarized in the term ocean acidification (OA). Already today, coastal regions experience episodic pH events during which surface layer pH drops below values projected for the surface ocean at the end of the century. Future OA is expected to further enhance the intensity of these coastal extreme pH events. To evaluate the influence of such episodic OA events in coastal regions, we deployed eight pelagic mesocosms for 53 days in Raunefjord, Norway, and enclosed 56–61 m3 of local seawater containing a natural plankton community under nutrient limited post-bloom conditions. Four mesocosms were enriched with CO2 to simulate extreme pCO2 levels of 1978 – 2069 μatm while the other four served as untreated controls. Here, we present results from multivariate analyses on OA-induced changes in the phyto-, micro-, and mesozooplankton community structure. Pronounced differences in the plankton community emerged early in the experiment, and were amplified by enhanced top-down control throughout the study period. The plankton groups responding most profoundly to high CO2 conditions were cyanobacteria (negative), chlorophyceae (negative), auto- and heterotrophic microzooplankton (negative), and a variety of mesozooplanktonic taxa, including copepoda (mixed), appendicularia (positive), hydrozoa (positive), fish larvae (positive), and gastropoda (negative). The restructuring of the community coincided with significant changes in the concentration and elemental stoichiometry of particulate organic matter. Results imply that extreme CO2 events can lead to a substantial reorganization of the planktonic food web, affecting multiple trophic levels from phytoplankton to primary and secondary consumers.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Drivers of Particle Sinking Velocities in the Peruvian Upwelling System (2023)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-02-07
    Description: As one of Earth's most productive marine ecosystems, the Peruvian upwelling system transports large amounts of biogenic matter from the surface to the deep ocean. Whilst particle sinking velocity is a key factor controlling the biological pump, thereby affecting carbon sequestration and O2-depletion, it has not yet been measured in this system. During a 50 d mesocosm experiment in the surface waters off the coast of Peru, we assessed particle sinking velocities and their biogeochemical and physical drivers. We further characterized the general properties of exported particles under different phytoplankton communities and nutritional states. Average sinking velocities varied between size classes and ranged from 12.8 ± 0.7 m d−1 (particles 40–100 µm) to 19.4 ± 0.7 m d−1 (particles 100–250 µm) and 34.2 ± 1.5 m d−1 (particles 250–1000 µm) (± 95 % CI). Despite a distinct plankton succession from diatoms to dinoflagellates with concomitant 5-fold drop in opal ballasting, substantial changes in sinking velocity were not observed. This illustrates the complexity of counteracting factors driving the settling behaviour of marine particles. In contrast, we found higher sinking velocities with increasing particle size and roundness and decreasing porosity. Size had by far the strongest influence among these physical particle properties, despite a high amount of unexplained variability. Our study provides a detailed analysis of the drivers of particle sinking velocity in the Peruvian upwelling system, which allows modellers to optimize local particle flux parameterization. This will help to better project oxygen concentrations and carbon sequestration in a region that is subject to substantial climate-driven changes.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    The appendicularian Oikopleura dioica can enhance carbon export in a high CO2 ocean (2024)
    Wiley
    Details
    Publication Date: 2024-02-02
    Description: Gelatinous zooplankton are increasingly recognized to play a key role in the ocean's biological carbon pump. Appendicularians, a class of pelagic tunicates, are among the most abundant gelatinous plankton in the ocean, but it is an open question how their contribution to carbon export might change in the future. Here, we conducted an experiment with large volume in situ mesocosms (~55–60 m3 and 21 m depth) to investigate how ocean acidification (OA) extreme events affect food web structure and carbon export in a natural plankton community, particularly focusing on the keystone species Oikopleura dioica, a globally abundant appendicularian. We found a profound influence of O. dioica on vertical carbon fluxes, particularly during a short but intense bloom period in the high CO2 treatment, during which carbon export was 42%–64% higher than under ambient conditions. This elevated flux was mostly driven by an almost twofold increase in O. dioica biomass under high CO2. This rapid population increase was linked to enhanced fecundity (+20%) that likely resulted from physiological benefits of low pH conditions. The resulting competitive advantage of O. dioica resulted in enhanced grazing on phytoplankton and transfer of this consumed biomass into sinking particles. Using a simple carbon flux model for O. dioica, we estimate that high CO2 doubled the carbon flux of discarded mucous houses and fecal pellets, accounting for up to 39% of total carbon export from the ecosystem during the bloom. Considering the wide geographic distribution of O. dioica, our findings suggest that appendicularians may become an increasingly important vector of carbon export with ongoing OA.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    KOSMOS 2017 Peru mesocosm study: single particle measurements of sinking velocity and physical properties (2023)
    PANGAEA
    Details
    Publication Date: 2024-03-06
    Description: As one of Earth's most productive marine ecosystems, the Peruvian Upwelling System transports large amounts of biogenic matter from the surface to the deep ocean. Whilst particle sinking velocity is a key factor controlling the biological pump, thereby affecting carbon sequestration and oxygen-depletion, it has not yet been measured in this system. During a 50-day mesocosm experiment in the surface waters off the coast of Peru, we regularly sampled sedimented material (sampling depth: 17 m) and analyzed the properties of sinking particles using an optical measurement approach. The presented dataset includes sinking velocity, particle size (ESD), compactness (porosity) and shape (aspect ratio) of 〉100.000 individually measured particles.
    Keywords: Aspect ratio; Climate - Biogeochemistry Interactions in the Tropical Ocean; DATE/TIME; Day of experiment; DEPTH, water; Equivalent spherical diameter; Experimental treatment; export flux; KOSMOS_2017; KOSMOS_2017_Peru; KOSMOS Peru; MESO; mesocosm experiment; Mesocosm experiment; Mesocosm label; Particle porosity; Peruvian Upwelling System; Phytoplankton; Sample code/label; SFB754; sinking velocity; Sinking velocity
    Type: Dataset
    Format: text/tab-separated-values, 821688 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 8
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    Oikopleura dioica, phytoplankton, and carbon export during the KOSMOS Bergen mesocosm experiment on ocean acidification (Raunefjord, Norway, 2015) (2023)
    PANGAEA
    Details
    Publication Date: 2024-03-06
    Description: This dataset is from an experiment with large-volume in situ mesocosms (~55-60 m3 and 21 m depth) in Raunefjord (Bergen), Norway in 2015. In this pelagic in situ mesocosm experiment, we assessed how ocean acidification (particularly episodic extreme events) affect natural plankton communities. A particular focus was the response of the appendicularian Oikopleura dioica, and its influence on vertical carbon fluxes. Therefore, we sampled ecological and biogeochemical key parameters for 49 days in regular intervals.
    Keywords: Appendicularia; Area/locality; Biological pump; Carbon, organic, particulate, flux; Carbon, organic, particulate, suspended; carbon export; Counting; DATE/TIME; Day of experiment; Elemental analyser; Event label; Field experiment; Flow cytometry Accuri C6; KOSMOS_2015; KOSMOS_2015_Mesocosm-M1; KOSMOS_2015_Mesocosm-M2; KOSMOS_2015_Mesocosm-M3; KOSMOS_2015_Mesocosm-M4; KOSMOS_2015_Mesocosm-M5; KOSMOS_2015_Mesocosm-M6; KOSMOS_2015_Mesocosm-M7; KOSMOS_2015_Mesocosm-M8; KOSMOS Bergen; larvacea; MESO; mesocosm experiment; Mesocosm experiment; Mesocosm label; Microphytoplankton, biomass as carbon; Nanophytoplankton, biomass as carbon; Ocean acidification; Oikopleura dioica; Oikopleura dioica, length; Picophytoplankton, biomass as carbon; POC flux; Treatment: partial pressure of carbon dioxide; Type of study; Zooplankton
    Type: Dataset
    Format: text/tab-separated-values, 2205 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 9
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    KOSMOS 2017 Peru mesocosm study: export flux and particle sinking velocities (2023)
    PANGAEA
    Details
    Publication Date: 2024-03-06
    Description: As one of Earth's most productive marine ecosystems, the Peruvian Upwelling System transports large amounts of biogenic matter from the surface to the deep ocean. Whilst particle sinking velocity is a key factor controlling the biological pump, thereby affecting carbon sequestration and oxygen-depletion, it has not yet been measured in this system. During a 50-day mesocosm experiment in the surface waters off the coast of Peru, we regularly measured particle sinking velocities and their biogeochemical and physical drivers. We further characterized the general properties of sinking matter (sampling depth: 17 m) under different phytoplankton communities and nutritional states. This dataset contains mean velocities of sinking particles as well as their median size, compactness and shape. We further included the particulate organic carbon flux, the sinking matter nitrogen to phosphorus ratio and the relative contribution of opal and particulate inorganic carbon to the total flux. The particle flux characteristics are complemented by measurements of chlorophyll a concentration in the water column and the relative contribution of diatoms to total chlorophyll a.
    Keywords: Aspect ratio; Biogenic silica; Carbon, inorganic, particulate; Carbon, organic, particulate, flux per day; Chlorophyll a; Chlorophyll a, Diatoms; Climate - Biogeochemistry Interactions in the Tropical Ocean; DATE/TIME; Day of experiment; Depth, bottom/max; Depth, top/min; DEPTH, water; Equivalent spherical diameter; Experimental treatment; export flux; KOSMOS_2017; KOSMOS_2017_Peru; KOSMOS Peru; MESO; mesocosm experiment; Mesocosm experiment; Mesocosm label; Nitrogen/Phosphorus ratio; Particle porosity; Peruvian Upwelling System; Phytoplankton; Sediment trap; SFB754; sinking velocity; Sinking velocity
    Type: Dataset
    Format: text/tab-separated-values, 3317 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 10
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    Seawater carbonate chemistry and environmental data, and nutrients of KOSMOS Bergen 2015 mesocosm study (2021)
    PANGAEA
    Details
    Publication Date: 2024-03-22
    Description: The oceans' uptake of anthropogenic carbon dioxide (CO2) decreases seawater pH and alters the inorganic carbon speciation – summarized in the term ocean acidification (OA). Already today, coastal regions experience episodic pH events during which surface layer pH drops below values projected for the surface ocean at the end of the century. Future OA is expected to further enhance the intensity of these coastal extreme pH events. To evaluate the influence of such episodic OA events in coastal regions, we deployed eight pelagic mesocosms for 53 days in Raunefjord, Norway, and enclosed 56–61 m**3 of local seawater containing a natural plankton community under nutrient limited post-bloom conditions. Four mesocosms were enriched with CO2 to simulate extreme pCO2 levels of 1978-2069 μatm while the other four served as untreated controls. Here, we present results from multivariate analyses on OA-induced changes in the phyto-, micro-, and mesozooplankton community structure. Pronounced differences in the plankton community emerged early in the experiment, and were amplified by enhanced top-down control throughout the study period. The plankton groups responding most profoundly to high CO2 conditions were cyanobacteria (negative), chlorophyceae (negative), auto- and heterotrophic microzooplankton (negative), and a variety of mesozooplanktonic taxa, including copepoda (mixed), appendicularia (positive), hydrozoa (positive), fish larvae (positive), and gastropoda (negative). The restructuring of the community coincided with significant changes in the concentration and elemental stoichiometry of particulate organic matter. Results imply that extreme CO2 events can lead to a substantial reorganization of the planktonic food web, affecting multiple trophic levels from phytoplankton to primary and secondary consumers.
    Keywords: Alkalinity, total; Alkalinity, total, standard deviation; Ammonium; Aragonite saturation state; Aragonite saturation state, standard deviation; Bicarbonate ion; Bicarbonate ion, standard deviation; Biogenic silica; Biomass/Abundance/Elemental composition; Calcite saturation state; Calcite saturation state, standard deviation; Calculated using seacarb; Calculated using seacarb after Nisumaa et al. (2010); Calculated using seacarb after Orr et al. (2018); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbon, organic, particulate; Carbon, organic, particulate/Nitrogen, organic, particulate ratio; Carbon, organic, particulate/Phosphorus, particulate ratio; Carbon, total, particulate; Carbonate ion; Carbonate ion, standard deviation; Carbonate system computation flag; Carbon dioxide; Carbon dioxide, standard deviation; Chlorophyceae indeterminata, biomass as carbon; Chlorophyll a; Chlorophyll a, standard deviation; Chrysophyceae indeterminata, biomass as carbon; Coast and continental shelf; Community composition and diversity; Cryptophyceae indeterminata, biomass as carbon; Cyanophyceae, biomass as carbon; DATE/TIME; Day of experiment; Diatoms indeterminata, biomass as carbon; Dinophyceae indeterminata, biomass as carbon; Entire community; Event label; Field experiment; Fjord; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Fugacity of carbon dioxide in seawater, standard deviation; KOSMOS_2015; KOSMOS_2015_Mesocosm-M1; KOSMOS_2015_Mesocosm-M2; KOSMOS_2015_Mesocosm-M3; KOSMOS_2015_Mesocosm-M4; KOSMOS_2015_Mesocosm-M5; KOSMOS_2015_Mesocosm-M6; KOSMOS_2015_Mesocosm-M7; KOSMOS_2015_Mesocosm-M8; KOSMOS_2015_Mesocosm-M9; KOSMOS Bergen; MESO; Mesocosm experiment; Mesocosm label; Mesocosm or benthocosm; Nitrate; Nitrate and Nitrite; Nitrite; Nitrogen, organic, particulate; Nitrogen, organic, particulate/Phosphorus, organic, particulate ratio; Nitrogen, total, particulate; North Atlantic; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide, standard deviation; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Particulate inorganic carbon/particulate organic carbon ratio; Pelagos; pH; pH, standard deviation; Phosphate; Phosphate, total, particulate; Potentiometric titration; Prasinophyceae indeterminata, biomass as carbon; Primary production/Photosynthesis; Prymnesiophyceae indeterminata, biomass as carbon; Ratio; Salinity; Salinity, standard deviation; Silicate; Temperate; Temperature, water; Temperature, water, standard deviation; Type
    Type: Dataset
    Format: text/tab-separated-values, 18566 data points
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    DATA PANGAEA
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