KOSMOS 2023 Helgoland mesocosm study on ocean alkalinity enhancement: Microbial metabolic rates
type: Dataset
conforms to: http://mlcommons.org/croissant/1.0
creator: Laura Marín-Samper
creator: Javier Arístegui
creator: Giulia Faucher
creator: Leila Kittu
creator: Maarten Boersma
creator: Ulf Riebesell
publisher: PANGAEA
  type: Organization
  disambiguating description: Data Publisher for Earth & Environmental Science
included in data catalog: PANGAEA
  type: DataCatalog
  disambiguating description: Data Publisher for Earth & Environmental Science
date published: 2026-07-27
additional type: dataset
description: Ocean alkalinity enhancement (OAE) is a marine carbon dioxide removal (mCDR) approach that can also mitigate ocean acidification. However, its biological impacts are expected to depend on the magnitude, timing, and dilution of alkalinity additions. To investigate these factors, a mesocosm experiment simulated hydrated lime additions using two six-level alkalinity gradients (up to ΔTA 1250 µmol kg⁻¹): one with immediate full-column mixing and another with mixing delayed by two days. These treatments simulated rapid (e.g. from a moving vessel in open ocean) and slow (e .g. point source or land-based applications in poorly mixed environments)dilution scenarios, representing different hydrodynamic conditions that may occur following real-world alkalinity additions. Gross production (GP), net community production (NCP) and community respiration (CR), determined from in vitro oxygen production and consumption, together with chlorophyll a, were monitored over a 35-day period. Spring bloom initiation was delayed non-linearly at low fCO₂, with reduced absolute and biomass-normalized production occurring in treatments exposed to fCO₂ below ~70 and 30 µatm respectively. These findings indicate that phytoplankton communities may be generally resilient to realistic OAE scenarios while helping to define ecologically relevant fCO₂ thresholds for safe OAE deployment.
abstract: Ocean alkalinity enhancement (OAE) is a marine carbon dioxide removal (mCDR) approach that can also mitigate ocean acidification. However, its biological impacts are expected to depend on the magnitude, timing, and dilution of alkalinity additions. To investigate these factors, a mesocosm experiment simulated hydrated lime additions using two six-level alkalinity gradients (up to ΔTA 1250 µmol kg⁻¹): one with immediate full-column mixing and another with mixing delayed by two days. These treatments simulated rapid (e.g. from a moving vessel in open ocean) and slow (e .g. point source or land-based applications in poorly mixed environments)dilution scenarios, representing different hydrodynamic conditions that may occur following real-world alkalinity additions. Gross production (GP), net community production (NCP) and community respiration (CR), determined from in vitro oxygen production and consumption, together with chlorophyll a, were monitored over a 35-day period. Spring bloom initiation was delayed non-linearly at low fCO₂, with reduced absolute and biomass-normalized production occurring in treatments exposed to fCO₂ below ~70 and 30 µatm respectively. These findings indicate that phytoplankton communities may be generally resilient to realistic OAE scenarios while helping to define ecologically relevant fCO₂ thresholds for safe OAE deployment.
citation: Microbial metabolic rates under ocean alkalinity enhancement: A step towards a safe operating space
  type: CreativeWork
  type: ScholarlyArticle
  creator: Laura Marín-Samper
  creator: Javier Arístegui
  creator: Giulia Faucher
  creator: Leila Kittu
  creator: Maarten Boersma
  creator: Ulf Riebesell
  is part of: Communications Earth & Environment
  creative work status: in press
  additional type: journal article
spatial coverage: Place
  geo: GeoCoordinates
    latitude: 54.183300000000024
    longitude: 7.900000000000001
temporal coverage: 2023-03-14T00:00:00/2023-04-17T00:00:00
funding: DAM CDRmare - RETAKE, GEOMAR
  type: MonetaryGrant
  funder: Federal Ministry of Education and Research
funding: Network of Leading European AQUAtic MesoCOSM Facilities Connecting Mountains to Oceans from the Arctic to the Mediterranean
funding: OceanNETs: Ocean-based Negative Emission Technologies
size: QuantitativeValue
  value: 2798.0
  unit text: data points
variable measured: Type of study
  type: PropertyValue
  subject of: DefinedTermSet
    has defined term: type
variable measured: Event label
variable measured: Day of experiment
  type: PropertyValue
  unit text: day
  subject of: DefinedTermSet
    has defined term: day
    has defined term: Time
variable measured: DATE/TIME
  type: PropertyValue
  subject of: DefinedTermSet
    has defined term: Time
variable measured: Identification number
  type: PropertyValue
  description: Mesocosm number
variable measured: Treatment: dilution type
  type: PropertyValue
  description: Dil_Treat
  subject of: DefinedTermSet
    has defined term: treatment
variable measured: Treatment: alkalinity, total
  type: PropertyValue
  unit text: µmol/kg
  description: Delta_TA
  subject of: DefinedTermSet
    has defined term: treatment
    has defined term: total
    has defined term: Molar Concentration
variable measured: Treatment
  type: PropertyValue
  subject of: DefinedTermSet
    has defined term: treatment
variable measured: Sample code/label
variable measured: Respiration rate, oxygen, community
  type: PropertyValue
  unit text: µmol/l/day
  description: CR: Community Respiration (amount of oxygen respired in the dark)
  subject of: DefinedTermSet
    has defined term: respiration rate
    has defined term: oxygen
    has defined term: Reaction Rate
variable measured: Net community production of oxygen
  type: PropertyValue
  unit text: µmol/l/day
  subject of: DefinedTermSet
    has defined term: net community production
      type: DefinedTerm
      alternate name: NCP
    has defined term: oxygen
    has defined term: Reaction Rate
variable measured: Gross community production of oxygen
  type: PropertyValue
  unit text: µmol/l/day
  subject of: DefinedTermSet
    has defined term: oxygen
    has defined term: Reaction Rate
variable measured: Balance
  type: PropertyValue
  description: GPR: Metabolic Balance = GCP/CR
  subject of: DefinedTermSet
    has defined term: balance
variable measured: Depth, description
  type: PropertyValue
  subject of: DefinedTermSet
    has defined term: depth
    has defined term: description
keywords: metabolic rates; ocean alkalinity enhancement; Ocean Alkalinity Enhancement (OAE); Phytoplankton; Primary production
license: https://creativecommons.org/licenses/by/4.0/
conditions of access: access rights needed
is accessible for free: false
language: en
distribution: data matrix.tab
distribution: FileObject
  type: DataDownload
  encoding format: text/html

Laura Marín-Samper
type: Person
family name: Marín-Samper
given name: Laura

Javier Arístegui
type: Person
family name: Arístegui
given name: Javier

Giulia Faucher
type: Person
family name: Faucher
given name: Giulia
affiliation: GEOMAR - Helmholtz Centre for Ocean Research Kiel

GEOMAR - Helmholtz Centre for Ocean Research Kiel
type: Organization
alternate name: GEOMAR

Leila Kittu
type: Person
family name: Kittu
given name: Leila
affiliation: GEOMAR - Helmholtz Centre for Ocean Research Kiel

Maarten Boersma
type: Person
family name: Boersma
given name: Maarten
affiliation: Alfred Wegener Institute for Polar and Marine Research, Bremerhaven (1986-2013)

Alfred Wegener Institute for Polar and Marine Research, Bremerhaven (1986-2013)
type: Organization
alternate name: AWI

Ulf Riebesell
type: Person
family name: Riebesell
given name: Ulf
affiliation: GEOMAR - Helmholtz Centre for Ocean Research Kiel

Federal Ministry of Education and Research
type: Organization
alternate name: BMBF

Network of Leading European AQUAtic MesoCOSM Facilities Connecting Mountains to Oceans from the Arctic to the Mediterranean
type: MonetaryGrant
funder: Horizon 2020 of the European Commission

Horizon 2020 of the European Commission
type: Organization
alternate name: H2020

OceanNETs: Ocean-based Negative Emission Technologies
type: MonetaryGrant
funder: Horizon 2020 of the European Commission

Time
type: DefinedTerm
alternate name: T

oxygen
type: DefinedTerm
alternate name: O

balance
type: DefinedTerm

depth
type: DefinedTerm

data matrix.tab
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type: DataDownload
encoding format: text/tab-separated-values