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Water and sediment analysis from column experiments

This data set contains data from water analyses from column experiments. The water analyses included cations (sodium, potassium, calcium, magnesium, iron and manganese), anions (nitrate, chloride, sulphate, bromide and phosphate) and selected trace elements (arsenic, cobalt, nickel, vanadium and zinc). The column experiments were conducted with two different types of unconsolidated sandy sediments from aquifers in Denmark (Quaternary) and Germany (Cretaceous). In both sediments, the nitrate degradation capacity was almost exhausted. To induce denitrification, 5 mmol ethanol was added to the column experiments. This also caused a decrease in the concentration of trace elements in the water. A sequential extraction procedure was performed to determine the trace element sinks. The data set therefore also contains contents of selected elements (equal to water analyses) from the sequential extraction procedure of the sediment before and after the column tests. The results observed in the laboratory were additionally modeled with Phreeqc. The Phreeqc input data complete the data set.

Landesmessstellen (überblicksweise Überwachung des chemischen Zustandes)

Landesmeßnetz zur Überwachung der Grundwasserbeschaffenheit im Hauptgrundwasserleiter gemäß der Kriterien der Wasserrahmenrichtlinie (WRRL).

Light effects on the vertical positioning of the freshwater jellyfish (Craspedacusta sowerbii Lankester, 1880)

We experimentally manipulated the presence of light and light intensity (F = 36.7 μmol m⁻² s⁻¹; D = 0 μmol m⁻² s⁻¹; L = 4.8 μmol m⁻² s⁻¹; M = 21.4 μmol m⁻² s⁻¹) and tested their effects on the vertical positioning of the freshwater jellyfish (Craspedacusta sowerbii) medusae. For the experiments, approximately 100 C. sowerbii medusae were collected in August 2017 in two lakes (Haager Weiher and Leitner Weiher) in Bavaria, Germany. Testing was carried out at Seeon Limnological Station in close vicinity to the collection site. The experimental columns were 7.4 cm in diameter and 170 cm high and were marked with horizontal lines every 5 cm for visual position estimation. Four replicates run in parallel. One C. sowerbii medusa was used in each experimental column. Data cover three light treatments, each run twice: 1) 16:8 h full light (F)–dark (D) light intensity cycles (nF = 716, nD = 428), 2) 16:8 h full light (F)–full dark (D) light intensity cycles complemented with low (L) and medium (M) light intensities (nF = 96, nM = 96, nL = 48, nD = 288), and 3) altered light intensities in approximately 2-hour periods randomly among dark, low, medium, and full light intensities (nF = 96, nM = 76, nL = 72, nD = 336). Results show that light alone was sufficient to trigger a vertical position change of jellyfish towards the water surface, especially high light.

Porewater chemistry, iron extractions, metabolic rates and microbial analyses from Boknis Eck sediments from January 2022 until March 2023

We collected sediments for pore water analyses via IC, ICP-OESm H2S and Alkalinity measurements, conducted sequential Fe-extractions, determined O2 consumption rates via an enclosed mini Chamber, measured sulfate reduction rates via 35S-SO4 tracer and conducted 16S rRNA amplicon gene analyses (seqeuncing Illumina). Data was generated from Boknis Eck sediments from January 2022 until March 2023.

Time series of environmental parameters of habitats along the Schleswig-Holstein Baltic Sea (2018 et seq)

The here presented data time-series are connected to the publication "Environmental parameters of shallow water habitats in the SW Baltic Sea" (Franz, M. et al. 2019b). Since 2019 a number of stations were added, and, hence, new time-series started. Every year a new dataset will be published including both, old and new stations. The following abstract is revised from Franz, M. et al. (2019b): The coastal areas of the Baltic Sea represent highly variable environments. In order to record the environmental conditions in shallow water habitats of the SW Baltic Sea, a monitoring program was established. The monitoring sites are located along the Baltic Sea coast of Schleswig-Holstein, Germany. Along the coast, 23 stations were established, where samplings for dissolved inorganic nutrient concentrations are conducted. Here, twice per month, water samples are collected in a water depth of 0.5 m. The samples are analysed for the concentration of dissolved inorganic nutrients (total oxidized nitrogen, nitrite, ammonia, phosphate and silicate) by UV/VIS spectroscopy using a continuous flow analyser (type QuAAtro 30; comp. SEAL Analytical, Hamburg, Germany. The system is equipped with a SEAL XY-2 autosampler). Quality control for nutrient measurements is ensured by certified reference material (CRM) by KANSO TECHNOS CO, LTD, Osaka, Japan. Additionally, at four shallow water stations (Booknis Eck, Bülk, Behrensdorf and Katharinenhof) temperature, salinity and dissolved oxygen are continuously logged at 2-3 m depth by self-contained data loggers. These are: (I) MiniDOT loggers (Precision Measurement Engineering; http://pme.com; ±10 µmol L-1 or ±5 % saturation) including antifouling copper option (copper plate and mesh) to measure dissolved oxygen concentration and (II) DST CT salinity & temperature loggers (Star-Oddi; http://star-oddi.com; ±1.5 mS cm-1) to record the conductivity. Both sensor types additionally record water temperature with an accuracy of ± 0.1 °C. The sampling interval was set to 30 minutes for all parameters. Another seven stations for continuous recordings of environmental parameters (again: temperature, salinity, dissolved oxygen) with the same two types of sensors were installed at 4-6 m depth in the context to the long-term monitoring project RegLocDiv (Regional-Local-Diversity) by M. Wahl (Franz, M. et al. 2019a) and included into this data set. These stations are at: Falshoeft, Booknis Eck, Schoenberg, Westermakesdorf, Staberhuk, Kellenhusen and Salzhaff (abandoned in 2023). Since 2021, in the context of implementing a reef monitoring to fulfil obligations by the EU Habitats Directive, step-by-step, eleven further stations were installed at reefs in the Schleswig-Holstein Baltic Sea. These are at: Platengrund (14 m depth) and Mittelgrund (8 m) (both since 2021), at Walkyriengrund (9 m), Brodtener Ufer (8 m), Außenschlei (11 m), Kalkgrund (8 m), Stollergrund (7.5 m) and Flueggesand (10 m) (all since 2022), as well as at Gabelsflach (10 m), Sagasbank (8.5 m) and Stabehuk (11.5 m) (all since 2023). Again, at all of these 11 stations, temperature, salinity and dissolved oxygen are continuously logged by self-contained data loggers: Conductivity (and temperature) is logged by HOBO® Salt Water Conductivity/Salinity Data Logger (Onset Computer Corporation, Bourne, MA, USA; https://www.onsetcomp.com) using the U2X protective housing to prevent fouling on the sensors. The same MiniDOT loggers (Precision Measurement Engineering) as at the above mentioned more shallow stations (including antifouling copper plate and mesh) are used to measure dissolved oxygen concentration. Dissolved oxygen concentration data measured by the MiniDOT loggers are corrected for a depth of 5 m (or 2,5 m on the shallow stations) using the software provided by the manufacturer. Additionally, a manual compensation for salinity was calculated (see details in Franz, M. et al. 2019b). Quality control was carried out by spike and gradient tests, following recommendations of SeaDataNet quality control procedures (see https://seadatanet.org/Standards/Data-Quality-Control). All data values were flagged according to applied quality checks using the following flags: 1 = Pass, 2 = Suspect, 3 = Fail, 4 = Visually suspect, 5 = Salinity compensation fail (further explanations can be found in Franz, M. et al. 2019b). The project is funded by the LfU (Landesamt für Umwelt, Schleswig-Holstein, Germany). Main responsible persons are C. Hiebenthal, C. Lieberum, F. Weinberger and R. Karez. Responsible for the nutrient analysis: N. Stärck; Responsible for taking the water samples: C. Lieberum and D. Bürger.

Water column, solid phase and porewater data in the Kiel Bight, SW Baltic Sea from 2016 to 2025

During the research cruises BE03/2016 (08.03.2016), BE10/2016 (19.10.2016), BE10/2018 (23.10.2018), BE03/2019 (15.03.2019), L23-13 (13.09.2023 - 15.09.2023), Sagitta24-1 (16.09.2024), Sagitta24-2 (23.09.2024), Hai24VE2 (24.09.2024), L25-2b (09.02.2025 - 17.02.2025) and EMB374 (04.09.2025 - 13.09.2025), CTDs were deployed and sediment corers were retrieved at 99 stations in Kiel Bight in the southwestern Baltic Sea. Water column oxygen concentrations were determined using oxygen sensors attached to the CTD framework. At selected water depths, water samples were collected with Niskin bottles for the analysis of nitrate concentrations using an autoanalyzer. Short sediment cores (<50cm) were recovered using a Multicorer (MUC), Minicorer (MIC) or Rumohrlot (RL). Bottom waters were sampled from the supernatant water in the sediment cores. Solid phase sediment samples were analyzed for total organic carbon using an element analyzer. Porewater was extracted from the sediment cores using rhizones and analyzed for total alkalinity (titration), ammonium (photometer), sulfate (ion chromatography), hydrogen sulfide (photometer), dissolved iron (ICP-OES) and dissolved manganese (ICP-OES). The collected data will be used to (i) determine the spatial and temporal variability of hydrogen sulfide in bottom waters of the Kiel Bight, (ii) identify the controlling factors governing the accumulation of hydrogen sulfide at the seafloor, and (iii) establish an early warning system of sulfidic seafloor conditions for regional stakeholders in the Baltic Sea.

Dissolved methane concentrations of water samples from the North Sea during ALKOR cruise AL575 (27 June 2022 - 13 July 2022)

Water sampling was conducted during AL575 cruise in the North Sea by using Niskin Bottles attached to CTD/Water sampler rosette and ROV (Haeckel and Schmidt, 2024). To detect methane anomalies in the water column derived from seafloor gas emissions the recovered water samples were processed by using headspace gas sampling and subsequent gas chromatographic analysis. Based on measured methane concentrations of headspace gas in (micro-atm) the dissolved methane concentrations in water were calculated (nmol l-1).

Surface water parameters (pH, specific conductivity, salinity, nutrients, oxygen, sulfate and chloride concentrations, DOC/DIC) (Table 4)

Surface water parameters were measured in parallel to the gas measurements and soil coring for microbial analyses. Most surface water variables (pH, specific conductivity, salinity, nutrients, oxygen, sulfate and chloride concentrations, DOC/DIC) were measured in-situ using a multiparameter digital water quality meter or taken to the laboratory as water samples for further analysis. While surface water analysis was only conducted in the drainage ditch before rewetting, it was done along the entire transect after rewetting.

Pore water and soil variables (pH, specific conductivity, nutrients, metals, sulfate and chloride concentrations, CNS) (Table 3)

Pore water parameters were measured in parallel to the gas measurements and soil coring for microbial analyses. Pore water/soil variables (pH, specific conductivity, nutrients, metals, sulfate and chloride concentrations, CNS) were either measured in-situ or taken to the laboratory as soil samples. Pore water/soil analysis was mostly conducted before rewetting and only repeated occasionally after rewetting where possible.

Phytoplankton pigment and phytoplankton group chlorophyll-a concentrations during POLARSTERN cruise PS126 from North Sea to Fram Strait in May to June 2021 from HPLC analysis of water samples

Phytoplankton pigments were determined in the water surface (from 0 to 11 m depth) of a transect from the North Sea to Fram Strait and back during RV Polarstern expedition PS126 from 24 May to 25 June 2021. Water samples were collected from CTD Niskin bottles at five to six different depths from the upper 100 m at CTD stations and from underway sampling. Between 0.4 to 3.5 L of each seawater sample was filtered through Whatman GF/F filters. The sample filters were then shock‐frozen in liquid N2 and kept at−80 °C until analysis. High Pressure Liquid Chromatography (HPLC) was performed to quantify various phytoplankton pigments (see Table 1 in Taylor et al. 2011) following the method of Barlow et al. (1997) that was adjusted to our temperature‐controlled instruments as detailed in Alvarez et al. (2022).

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