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Sediment characteristics in the muddy region in southeast of the island of Helgoland (North Sea)

Sediment were sampled on expedition HE625 of the R/V Heincke in July 2023 at 50 stations spread evenly over the muddy sediment region in southeast of the island of Helgoland (southeastern North Sea). At each station, two replicate samples were taken with a van Veen grab with a sampling area of 0.1 m² and a penetration depth of 10 cm. A subsample of the upper 6 cm of sediment was taken using a coring tube from the second grab with a diameter of 4.5 cm. The grain-size distribution was determined based on laser-diffraction granulometry using a CILAS 1180L particle size analyzer. Another sub-sample of 40 g of sediment were dried, weighed, and incinerated at 500 °C for five hours to estimate the organic content (%) as weight loss on combustion. Sediment variables included organic carbon content (OC), sediment composition (percentages of sand, silt, and clay), grain size (d10, d50, d90), and statistical measures of sediment grain size distribution (skewness, sorting, kurtosis).

Zoobenthos and sediments time series at List Reede, Sylt, Germany: pilot samples in 2001

In preparation for a forthcoming monitoring project, a shallow subtidal area in the northern Wadden Sea was studied for macrozoobenthos >1 mm sieve size. Using a Reineck-type box-corer of 0.02 m² surface area, abundance and specific composition were evaluated from a sampling grid of 21 positions with two replicates each. Temporarily, sampling was repeated 9 times. Analyses of spatial and temporal variability revealed that within-site variability was far lower than between-site variability. As a consequence, the later monitoring project was based on a higher number of study sites at the cost of within-site replication.

TOC, TIC, TN and TS contents and stable isotope signatures (δ13C of TOC, δ15N, δ34S) of fine-grained saltmarsh deposits of the barrier island Spiekeroog at the southern North Sea Coast

The dataset compiles total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN) and total sulfur (TS) contents and stable isotope signatures (δ13C of TOC, δ15N, δ34S) of fine-grained deposits (clay, loam) over sandy subsoils of the saltmarsh of the barrier island Spiekeroog at the southern North Sea coast. Sampling was performed in September 2016 along three transects spanning from the high saltmarsh to the pioneer zone. At each sample point, soil samples were taken from the first 5 cm of the upper part (top samples) and from the deepest 5 cm of the lower part (bottom samples) of the fine-grained deposit. If the fine-grained deposit layer had a thickness < 10 cm, only one bulk soil sample (single samples) was taken for the depth range equal to the deposit thickness. Samples were ground to fine powder. TIC was measured on oven-dried samples coulometrically with an Analytik Jena multi EA 4000 analyzer. The total carbon (TC), TN, and TS were analyzed using a Thermo Scientific Flash EA Isolink Elemental Analyzer. The TOC contents were calculated as the difference between TC and TIC. TOC, TN, and TS contents are reported based on the original dry mass. For isotope analysis, dried and homogenized samples were weighed in tin cups and combusted in a Thermo Scientific Flash EA Isolink Elemental Analyzer, connected to a Thermo Finnigan MAT 253 gas mass spectrometer via a Thermo Conflo IV split interface. The δ13C values of TOC were measured after decalcification of the ground powders with p. a. grade HCl. The TN and δ34S analysis were carried out on a separate aliquot of sample powder. The isotope results are given in the conventional δ-notation.

TOC, TIC, TN and TS contents and stable isotope signatures (δ13C of TOC, δ15N, δ34S) of fine-grained saltmarsh deposits of the barrier island Spiekeroog at the southern North Sea Coast

The dataset compiles total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN) and total sulfur (TS) contents and stable isotope signatures (δ13C of TOC, δ15N, δ34S) of fine-grained deposits (clay, loam) over sandy subsoils of the saltmarsh of the barrier island Spiekeroog at the southern North Sea coast. Sampling was performed in September 2016 along three transects spanning from the high saltmarsh to the pioneer zone. At each sample point, soil samples were taken from the first 5 cm of the upper part (top samples) and from the deepest 5 cm of the lower part (bottom samples) of the fine-grained deposit. If the fine-grained deposit layer had a thickness < 10 cm, only one bulk soil sample (single samples) was taken for the depth range equal to the deposit thickness. Samples were ground to fine powder. TIC was measured on oven-dried samples coulometrically with an Analytik Jena multi EA 4000 analyzer. The total carbon (TC), TN, and TS were analyzed using a Thermo Scientific Flash EA Isolink Elemental Analyzer. The TOC contents were calculated as the difference between TC and TIC. TOC, TN, and TS contents are reported based on the original dry mass. For isotope analysis, dried and homogenized samples were weighed in tin cups and combusted in a Thermo Scientific Flash EA Isolink Elemental Analyzer, connected to a Thermo Finnigan MAT 253 gas mass spectrometer via a Thermo Conflo IV split interface. The δ13C values of TOC were measured after decalcification of the ground powders with p. a. grade HCl. The TN and δ34S analysis were carried out on a separate aliquot of sample powder. The isotope results are given in the conventional δ-notation.

Hydroacoustic data collected during AL-519/1 in January 2019 in the German Bight

Biocrust and sediment characteristics of biological soil crusts in coastal sand dunes in northern Germany

This dataset comprises environmental parameters for biological soil crusts in coastal sand dunes in northern Germany. Biological soil crusts (biocrusts) are autonomous ecosystems consisting of prokaryotic and eukaryotic microorganisms growing on the topsoil. They colonize global climatic zones, including temperate dunes. This study examined changes in the community structure of biocrust phototrophic organisms along a dune chronosequence at the Baltic Sea compared to an inland dune in Northern Germany. The community composition and their shift between different successional stages of dune development were related to physico-chemical sediment properties. A vegetation survey followed by species determination and sediment analyses were conducted. The sampling took place on the 25th of April and on the 5th of May 2020. The samples were collected at a costal dune area, namely the Schaabe spit on the island Rügen, Mecklenburg Wester-Pomerania, Germany, and in an inland dune area at Verden (Aller), Lower Saxony, Germany. Biocrust samples were taken along one transect per study site. Each transect followed a natural succession gradient in the dune area. Along each transect, the different successional dune stages were visually identified and further named as dune subsites. At each subsite, a sampling plot of 1 m2 was established and used for further vegetation analyses, biocrust and sediment sampling. Along the Schaabe spit transect four subsites with one sampling plot each were established and three subsites were established in the inland dune in Verden. For the vegetation survey seven different functional groups were defined describing the overall surface coverage: Thin (1-3 mm) green algae-dominated biocrusts were defined as early successional stages. Later successional stages, in which the green algae biocrusts became slightly thicker (3-8 mm) and moss-covered, were defined as the intermediate successional biocrust stage. Moss-dominated biocrusts and those who additionally lichenized characterized the mature successional stages of biocrusts. Vascular plants, and litter (dead material, i.e., pine needles, leaves, and branches) were two of the non-cryptogamic but still biotic functional groups. Bare sediment was the only abiotic functional group. The predefined functional groups were recorded within each plot according to the point intercept method by Levy and Madden (1933). Each of the seven sampling plots was divided into 16 equal subplots (0.0625 m2). A 25 cm x 25 cm (0.0625 m2) grid of 25 intersections was placed randomly into 4 of these subplots. Within each sub-plot, the functional groups were recorded by 25 point measurements according to the approach of Williams et al. (2017). That allowed 100 point measurements per sampling plot (1 m2).

Morphological determination of the phototrophic community composition of biological soil crusts in coastal sand dunes in northern Germany

This dataset comprises the microbial community composition of biological soil crusts in north-German sand dunes. For this we obtained enrichment cultures of phototrophic microorganisms, by placing fragments of biocrusts of the same Petri dishes as used for sequencing, in Petri dishes with Bold Basal (1N BBM) agarized medium (Bischoff and Bold 1963). Cultures were grown under standard laboratory conditions: with a 12-hour alteration of light and dark phases and irradiation of 25 μmol photons m-2 s-1 at a temperature 20 ± 5 ºС. Microscopic study of these raw cultures began in the third week of cultivation. Morphological examinations were performed using Olympus BX53 light microscope with Nomarski DIC optics (Olympus Ltd, Hamburg, Germany). Micrographs were taken with a digital camera (Olympus LC30) attached to the microscope, and processed by the Olympus software cellSens Entry. Direct microscopy of rewetted samples was performed in parallel with cultivation for evaluation of dominating species of algae and cyanobacteria in the original samples. Morphological identification of the biocrust organisms was based mainly on Ettl and Gärtner (2014) for green microalgae, and on Komárek (2013) for cyanobacteria, as well as on some monographs and papers devoted to taxonomic revisions of the taxa of interest (Darienko and Pröschold 2019). Moss and lichens samples were air-dried after collection. For determination, a microscope with a maximum magnification of 400x was used. Morphological identification of mosses followed Frahm and Frey (2004) with taxonomical reference to (Hodgetts et al. 2020). Lichens were determined according to Wirth et al. (2013). Morphologically critical species of the genus Cladonia where additionally analyzed by thin-layer chromatography according to (Culberson and Ammann 1979) in solvent system A.

Microbial community composition of biological soil crusts in coastal sand dunes in northern Germany

This data collection comprises environmental data and taxonomic parameters of the investigated biocrusts of sampling sites in coastal and inland sand dunes in northern Germany. Sampling took place in spring 2020 and winter 2021. Biocrusts and uppermost sediment samples were collected along dune successional gradients and sequenced by LGC Genomics Ltd. Corresponding sequence data of biocrust organisms are archived at the European Nucleotide Archive.

Macrozoobenthos biomass in surface sediments of R/V Alkor cruise AL519/1

Hydroacoustic and Sediment data collected during AL-519/1 in January 2019 in the German Bight

During the research cruise AL-519-1 with RV Alkor the effects of dredging measures in an extraction site west off Sylt (German Bight) were investigated. Here, sandy material was extracted since 1984 for beach nourishment on the Island of Sylt. The extraction site lies approx. 7 km west of Sylt and has an extend of 5.5 km*3 km with water depths between 13 and 32 m. The investigations took place in January 2019 and lasted about five days. In order to assess the morphology of the study site, a gapless bathymetry was measured using a multibeam echosounder (ELAC Seabeam 1000, 180 kHz). For the determination of further seafloor characteristics and backscatter responses of the seafloor, a sidescan sonar were used (Imagenex YellowFin 872, 330 kHz). In addition, 55 sediment samples were taken in different domains of the study site (e.g. old dredging pits, new dredging pits, unaffected seafloor). The sediment samples were examined with regard to their grain sizes as well as their macrozoobenthos community composition.

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