Description: We conducted a mesocosm study to investigate ecosystem responses to ocean alkalinity enhancement (OAE) in the temperate waters of the German North Sea on Helgoland in spring 2023. We simulated non-CO2-equilibrated OAE via calcium hydroxide through the addition of calcium chloride and sodium hydroxide. Twelve 6 m³ mesocosms were used to simulate two scenarios: in six mesocosms we established a gradient of added alkalinity from 0 to 1250 µmol/kg in increments of 250 µmol/kg, simulating immediate (imm) dilution of alkalised waters. For the second set of six mesocosms, alkalinity was added only to the top 1 m of each mesocosm, doubling the target added alkalinity. The top layer was mixed with the untreated bottom layer after 48 hours, simulating delayed dilution of alkalised waters (del) and ultimately leading to the same alkalinity gradient as the immediate dilution treatment. This data contains water column biogeochemical variables, including dissolved inorganic nutrient concentrations (µmol/L), chlorophyll a concentrations (µg/L) and suspended particulate matter (biogenic silica, particulate organic carbon, nitrogen and phosphate; µmol/L). Nutrients, particulate organic phosphate and biogenic silica were measured spectrophotometrically (Unicam UV 300, Thermo Spectronic, USA). High-performance liquid chromatography (Thermo Scientific HPLC Ultimate 3000) was performed for chlorophyll a determination and particulate organic carbon and nitrogen were measured using an elemental analyser (Flash EA, Thermo Fisher).
Global identifier:
Doi(
"10.1594/PANGAEA.987501",
)
DataMeasurements(
DataMeasurements {
domain: Unspecified,
station: None,
measured_variables: [
"Biogenic silica",
"Carbon, organic, particulate",
"Chlorophyll a",
"Day of experiment",
"Depth, water, experiment, bottom/maximum",
"Depth, water, experiment, top/minimum",
"Event label",
"Mesocosm label",
"Nitrate",
"Nitrite",
"Nitrogen oxide",
"Nitrogen, organic, particulate",
"Phosphate",
"Phosphorus, organic, particulate",
"Sampling date/time, experiment",
"Silicate",
"Treatment",
"Treatment: alkalinity, total",
"Treatment: dilution type",
"Type of study",
"Water depth description",
],
methods: [
"Elemental analyser, Thermo Fisher, Flash EA",
"High-performance liquid chromatography (HPLC), Thermo Scientific, UltiMate 3000",
"Spectrophotometer, Thermo Spectronic, Unicam UV 300",
],
},
)
Comment: The empty cells in the data table refer to outliers that were removed from the dataset. --- Details regarding mesocosm set-up: The floating mesocosms were made of a transparent 1mm thick polyurethane bag with a cylindrical upper section and a conical sediment trap at the bottom, extending to 3.5 m depth. The bags were mounted on floating frames and enclosed a water volume of ~6m³. The mesocosms were filled simultaneously with seawater pumped from 2-3 m depth outside the harbour using a peristaltic pump, larger organisms were excluded via pre-filtration with a 3 mm mesh.
Tags: Stickstoffgehalt ? Gesamtphosphor ? Nitrit ? Siliziumdioxid ? Nitrat ? Kohlenstoff ? Nährstoff ? Phytoplankton ? Schwebstoff ? Stickstoff ? USA ? Stickoxide ? Studie ? Meeresgewässer ? Wasser ? Carbon Dioxide Removal ? Daten ? Ökosystem ? Wasseraufbereitung ? Gewässer ? Nordsee ? Nutrient data ? chlorophyll-a concentration ? mesocosm experiment ? ocean alkalinity enhancement ? particulate organic matter concentration ?
Region: Helgoland
Bounding boxes: 7.900000000000001° .. 7.900000000000001° x 54.183300000000024° .. 54.183300000000024° 7.8863° .. 7.8863° x 54.18143° .. 54.18143°
License: Creative Commons Namensnennung 4.0
Data access requires registration: click here for further informationLanguage: Englisch/English
Modified: 2025-12-02
Time ranges: 2023-03-14 - 2023-04-21
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