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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).

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.

Zoobenthos and sediments time series at List Reede, Sylt, Germany, in 2017

A shallow subtidal area in the northern Wadden Sea was monitored for sediment parameters and macrobenthic fauna using stratified random sampling of a grid of 33 sampling positions. Samples were collected with a Reineck-type box-corer of 0.02 m² surface area. Granulometric sediment composition was analysed from a sub-sample of each box-core using a diffraction laser particle-size analyser. Macrobenthos (sieved through 1 mm square meshes and fixed in buffered formalin solution) was counted, identified to species level, and the size of hard-shelled individuals measured. The amount of shell detritus was quantified as wet-weight in the benthos samples. This dataset contains the results from the sampling events in 2017.

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.

Zoobenthos and sediments time series at List Reede, Sylt, Germany, in 2019

A shallow subtidal area in the northern Wadden Sea was monitored for sediment parameters and macrobenthic fauna using stratified random sampling of a grid of 33 sampling positions. Samples were collected with a Reineck-type box-corer of 0.02 m² surface area. Granulometric sediment composition was analysed from a sub-sample of each box-core using a diffraction laser particle-size analyser. Macrobenthos (sieved through 1 mm square meshes and fixed in buffered formalin solution) was counted, identified to species level, and the size of hard-shelled individuals measured. The amount of shell detritus was quantified as wet-weight in the benthos samples. This dataset contains the results from the sampling events in 2019.

Zoobenthos and sediments time series at List Reede, Sylt, Germany, 2003 to 2019

A shallow subtidal area in the northern Wadden Sea was monitored over 17 years for sediment parameters and macrobenthic fauna using stratified random sampling of a grid of 50 sampling positions. Samples were collected with a Reineck-type box-corer of 0.02 m² surface area, always during preceeded high tide. Granulometric sediment composition was analysed from a sub-sample of each box-core using a diffraction laser particle-size analyser. Macrobenthos (sieved through 1 mm square meshes and fixed in buffered formalin solution) was counted, identified to species level, and the size of hard-shelled individuals measured. The amount of shell detritus was quantified as wet-weight in the benthos samples. From 2003 to 2007 sampling was approximatively monthly and from 2008 to 2013 seasonally. When a new ship with larger drought was put into operation, the number of sampling sites needed to be reduced to 33 from 2014 onwards and sampling frequency was only once per year in autumn.

FIRE-Tool: New tools in reconstructing wildfire history from sedimentary records using organic geochemical methods

The fire regimes of Australia, the most fire prone continent on earth, have been changing during the late Quaternary and up to the present under the influence of a changing climate and vegetation, Aboriginal impact and then by European settlers. Because fire history is an important parameter in understanding palaeoenvironmental conditions in many parts of the world, it has been reconstructed primarily by palynologists using lake cores and traditional tools (visible charcoal), combined with dating (14C, 210Pb, 137Cs) and the reconstruction of the past vegetation (pollen). Quantifying only (microscopically) visible charcoal may reflect charcoal from forest fires which are relatively large in size and structurally sound. However these techniques are less likely to quantify smaller charcoal fractions derived from grasses - probably the main contributor of charcoal in Australias vast savannas and open grassy woodlands. Therefore, we are developing a new methodology to infer past wildfires by using geochemical tools that potentially assess the whole range of fire residues in sedimentary records and that can yield additional information about the vegetation burned. In particular, we propose that a geochemical marker method (benzene polycarboxylic acids (BPCA)) would be capable to detect sedimentary fire residues that are too small to detect with standard microscopic methods. So far, however, these geochemical markers have not been used to quantify fire residues in lake sediment cores, neither have they been cross-compared to the presence of visible charcoal, which is indicative of palaeofires. The proof-of-concept study is conducted at two Australian sites where we would use molecular markers (BPCA) together with other geochemical methods to quantify past occurrences of fire and burned vegetation types. First we screen samples from about 200 depth intervals with a relatively rapid technique (MIR-PLS, mid-infrared spectroscopy with partial least square analysis) to observe major organic and inorcanic properties. Then, an in-depth, and more time-consuming characterization follows on some 20 samples from those sections of the cores, which have been identified by MIR-PLS to show significant changes in charcoal and organic carbon abundance. These sections will be analyzed using more sophisticated molecular scale techniques including the BPCA molecular marker method. (abridged text)

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

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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