The data were generated during an experiment simulating different frequencies of heatwaves (zero, one and three) in late spring/summer 2015. The experiment was carried out at the Kiel Outdoor Benthocosm (KOB) of GEOMAR Helmholtz Centre for Ocean Research Kiel, located at the Kiel Fjord.
The biomass of filamentous algae was quantified from the most abundant genus occurring inside the tanks, i.e. Ceramium sp. The biomass of Zostera marina and Fucus vesiculosus was estimated from growth rates measurements carried out every 15 days. The biomass of all macrophytes was converted to carbon using specific carbon contents measured concomitantly with stable isotopes (https://doi.pangaea.de/10.1594/PANGAEA.966179). Respiration and primary production measurements were carried out on 09.08.2015 for filamentous algae, and on 12.08.2015 for Fucus vesiculosus. To execute these measurements, organisms were kept in gas-tight cylindrical chambers equipped with sensor spots for non-invasive oxygen measurements, which allowed continuous oxygen logging. Throughout the measurements, the chambers were kept inside the KOB tanks to maintain the temperature. The oxygen values were converted to carbon and normalized by the area of the tank (1.53 m2) per day. Note that the data of net primary production and respiration rates of the Z. marina were previously published (https://doi.org/10.1594/PANGAEA.904632). The carbon flux refers to the exports, i.e. biomass that was floating in the tanks, which was considered as carbon leaving (i.e. exported outside of) the system but still usable. The material to quantify the exports was collected every seven days, separated accounting for the contribution of each macrophyte group, dried at 80 °C until the biomass was constant and weighted. The dry weight was converted to carbon using the specific carbon contents measured concomitantly with stable isotopes (https://doi.pangaea.de/10.1594/PANGAEA.966179), and normalized by the area of the tank (1.53 m2) per day.
The data refer to an experiment simulating different frequencies of heatwaves (zero, one and three) in late spring/summer 2015. The experiment was carried out at the Kiel Outdoor Benthocosm (KOB) of GEOMAR Helmholtz Centre for Ocean Research Kiel, located at the Kiel Fjord.
The organisms were collected from the mesocosm tanks, stored at -80 °C, dried at 60 °C for at least 48 hours, and ground with agate mortar and pestle. The ground material was subsampled, weighed and placed into tin capsules (3.2 × 4.0 mm, Hekatech, Wegberg, Germany). These samples were analysed with an elemental analyser system (NA 1110, Thermo, Milan, Italy) connected to a temperature-controlled gas chromatography oven (SRI 9300, SRI Instruments, Torrance, CA, USA) and to an isotope-ratio mass spectrometer (DeltaPlus Advantage, Thermo Fisher Scientific) as described in Hansen et al. (2009), https://doi.org/10.1002/rcm.4267.
Multispectral data from two legume-grass mixtures (clover- and lucerne-grass) were collected in the year 2018 for aboveground biomass and nitrogen fixation (NFix) estimation. In addition to the mixtures, pure stands of legumes and of grasses of the two mixtures were sown in order to represent variable conditions in practical farming (0-100% legumes). All six treatments were cultivated in four replicates and harvested three times within the year (plot size: 1.5 x 12 m). Destructive biomass samples for fresh (FM) and dry matter (DM) and NFix determination were taken three times at harvest. To cover the entire vegetation season, sub-sampling for DM and FM was done five times between the harvests. Flight missions were carried out one day before each of the eight sampling dates. A multispectral sensor (Parrot Sequoia, MicaSense Inc, Seattle, USA) with four spectral bands (green, red, red edge, near infrared) was mounted on a low-cost unmanned aerial vehicle (UAV; DJI Phantom 3, Advanced, Shenzhen, China). Eight black and white ground control points (GCPs) were distributed in the pathways. Coordinates of the plot corners and GCPs were measured by a Leica real time kinematic global navigation satellite system (Leica RTK GNSS). Orthomosaics were created by the overlapping images with a photogrammetric processing software (Agisoft PhotoScan Professional, Agisoft LLC, St. Petersburg, Russia). The orthomosaics were georeferenced using the coordinates of the GCPs. The mean reflectance value of the four bands was extracted by zonal statistics in QGIS (Quantum Geografic Infromation System) using the four plot corners of each plot as boundaries. Furthermore, eight texture features of every band were calculated, provided by the processing tool HaralickTextureExtraction of the Orfeo Toolbox library (OTB) in QGIS.
The data were generated during an experiment simulating different frequencies of heatwaves (zero, one and three) in late spring/summer. The experiment was carried out at the Kiel Outdoor Benthocosm (KOB) of GEOMAR Helmholtz Centre for Ocean Research Kiel, located at the Kiel Fjord.
The consumers were collected from the mesocosm tanks and the respiration rates were measured in the lab. The measurements were carried out on 10.08.2015 (Idotea balthica), 11.08.2015 (Littorina littorea) and 14.08.2015 (Gammarus sp.). The organisms were kept in gas-tight bottles equipped with sensor spots for non-invasive oxygen measurements, which allowed continuous oxygen logging. Throughout the measurements, the bottles were kept in water baths with temperature set to 19.7 °C, which was the temperature all the KOB tanks were exposed to at the time of the measurements. The oxygen values were converted to carbon and normalized by the area of the tank (1.53 m2) per day.