Schulz, Kai Georg; Schneider, Julieta; Riebesell, Ulf (2025): Carbonate chemistry speciation of the 2023 KOSMOS Helgoland experiment on the effects of ocean alkalinity enhancement on pelagic foodwebs [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.986507
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Published: 2025-10-14 • DOI registered: 2025-11-12
Abstract:
This dataset contains carbonate chemistry speciation data of the 2023 KOSMOS mesocosm study on Helgoland, Germany. This study tested the effects of ocean alkalinity enhancement simulating lime additions on pelagic ecosystem functioning during a spring bloom. Carbonate chemistry speciation (fCO2, pHT, calcium carbonate saturation state) was generally calculated from measurements of total alkalinity (TA) and dissolved inorganic carbon (DIC) in depth-integrated water samples. There were 12 mesocosms in total and in 6 of them an alkalinity gradient of up to +1250 umol/kg was established in steps of 250 umol/kg. In the remaining 6 the same amount of alkalinity was added only to the upper portion of the mesocosms, resulting in twice the alkalinity increase there, before being mixed in after 48 hours. The two treatments simulated the immediate dilution of TA after ship deployment as well as a delayed one from a point source.
Keyword(s):
Project(s):
Funding:
Federal Ministry of Education and Research (BMBF), grant/award no. 03F0895A: DAM CDRmare - RETAKE, GEOMAR
Coverage:
Latitude: 54.183300 * Longitude: 7.900000
Date/Time Start: 2023-03-14T00:00:00 * Date/Time End: 2023-04-21T00:00:00
Event(s):
KOSMOS_2023_Mesocosm-M1 * Latitude: 54.183300 * Longitude: 7.900000 * Date/Time Start: 2023-03-14T00:00:00 * Date/Time End: 2023-04-21T00:00:00 * Location: Helgoland * Campaign: KOSMOS_2023 (KOSMOS Helgoland) * Method/Device: Mesocosm experiment (MESO)
KOSMOS_2023_Mesocosm-M2 * Latitude: 54.183300 * Longitude: 7.900000 * Date/Time Start: 2023-03-14T00:00:00 * Date/Time End: 2023-04-21T00:00:00 * Location: Helgoland * Campaign: KOSMOS_2023 (KOSMOS Helgoland) * Method/Device: Mesocosm experiment (MESO) * Comment: delayed treatment
KOSMOS_2023_Mesocosm-M3 * Latitude: 54.183300 * Longitude: 7.900000 * Date/Time Start: 2023-03-14T00:00:00 * Date/Time End: 2023-04-21T00:00:00 * Location: Helgoland * Campaign: KOSMOS_2023 (KOSMOS Helgoland) * Method/Device: Mesocosm experiment (MESO)
Comment:
DIC and TA derived pHT regressed against depth-integrated CTD pH allowed to identify outliers
If outliers detected in TA or DIC, corrected CTD pH (regression R2 of 0.99) was used to calculate carbonate chemistry as second parameter
Data provide depth-integrated values (with the exception for the delayed treatments on day 5 and 6 where the data was from bottom layer samples). The T5 show data for the delayed treatments from day 3 to 7 where on day 3 and 7 the data shown is from depth-integrated samples while on day 5 and 6 it is from top layer samples.
On day 5 and 6, the top layer samples have also been taken by a Niskin (0.3-0.8m).
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | Type of study | Study type | Schulz, Kai Georg | |||
| 2 | Event label | Event | Schulz, Kai Georg | |||
| 3 | Sample code/label | Sample label | Schulz, Kai Georg | |||
| 4 | Day of experiment | DOE | day | Schulz, Kai Georg | ||
| 5 | Alkalinity, total | AT | µmol/kg | Schneider, Julieta | ||
| 6 | Carbon, inorganic, dissolved | DIC | µmol/kg | Schneider, Julieta | ||
| 7 | pH | pH | Schulz, Kai Georg | total scale | ||
| 8 | Fugacity of carbon dioxide | fCO2 | µatm | Schulz, Kai Georg | Carbonate chemistry calculated from measured TA and DIC | |
| 9 | Bicarbonate ion | [HCO3]- | µmol/kg | Schulz, Kai Georg | ||
| 10 | Carbonate ion | [CO3]2- | µmol/kg | Schulz, Kai Georg | ||
| 11 | Carbon dioxide, dissolved | CO2 diss | µmol/kg | Schulz, Kai Georg | ||
| 12 | Calcite saturation state | Omega Cal | Schulz, Kai Georg | Omega calculated using SAL and TEMP dependent solubilities, taking into account increase in [Ca2+] by salinity normalised TA increase, as well as decrease in TA in two instances due to CaCO3 formation | ||
| 13 | Aragonite saturation state | Omega Arg | Schulz, Kai Georg | |||
| 14 | Salinity | Sal | Schulz, Kai Georg | |||
| 15 | Temperature, water | Temp | °C | Schulz, Kai Georg |
License:
Creative Commons Attribution 4.0 International (CC-BY-4.0) (License comes into effect after moratorium ends)
Status:
Curation Level: Enhanced curation (CurationLevelC)
Size:
3840 data points
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