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We measured the following vascular plant functional traits: plant height (cm), leaf size (LS, cm2), specific leaf area (SLA, cm2 g-1), leaf dry matter content (LDMC, mg g-1) and leaf moisture content (g g-1) from the most common species in each research unit. We measured the following Sphagnum traits: capitulum density (number of shoots cm-2), fascicle density (number cm-1), surface density (mg cm-3), capitulum dry mass (mg) and capitulum moisture content (cap_wc, g g-1). In addition, rate of net photosynthesis was measured at four light levels. The data was collected from Lakkasuo mire complex located in Southern Finland (61° 47' N; 24° 18' E). The study includes three sites called rich fen, poor fen, and bog. At each site two experimental units were established in 2000/2001: an undrained control unit and a Water level drawdown (WLD) unit that was surrounded by a 30 cm-deep ditches after a control year. Photosynthesis measurements were carried out during summer 2016, while other traits were sampled during August 2016. We measured vascular plant vegetative height (cm), leaf area (LA, cm2 leaf-1) with a leaf area scanner (LI-3000, LI-COR Inc.), leaf fresh mass and leaf dry mass after the sample was dried at 40 °C for at least 48h (mg leaf-1). Leaf dry matter content (LDMC mg g-1) was calculated from fresh and dry mass, while specific leaf area (SLA, cm2 g-1) was calculated from LA and dry mass. Leaf traits were measured from five replicate plants as an average of a sample of ten fully grown healthy leaves from each plant. Sphagnum moss traits were measured from five replicates of single-species samples. Each sample consisted of two parts: a volume-specific sample collected with a core (diameter 7 cm, area 38.5 cm2, height 3 cm) to maintain the natural density of the stand and an additional sample of ca. 10 individuals, with stems more than 5 cm at length. Before collecting the core in the field, the number of shoots was counted from a 4 × 4 cm square for capitulum density (cap_dens, number of shoots cm-2). The volume-specific sample was cleaned of litter and unwanted species before drying at 40 °C for at least 48h to determine the surface density (surf_dens, mg cm-3). The additional sample of ten moss individuals was divided into capitula and stems (4 cm below capitula). We counted the number of fascicles on the 4 cm stem segments (fasc_dens, number cm-1). The capitula were thoroughly moistened and placed on top of tissue paper for 2 minutes to drain, before weighing them for water-filled fresh mass (cap_fw, mg). The samples were dried at 60 °C for at least 48h to measure the capitulum dry masses (cap_dw, mg). The moisture contents of capitula (cap_mc, g g-1) were then calculated as the ratio of water-filled to dry mass. Height growth (mm growing season-1) was measured in the field with the modified cranked wire method (Clymo 1970) as a difference in height between the beginning (mid-May) and end (mid-October) of the growing season 2017. For both vascular plants and mosses, we measured net photosynthesis rate, with a fully controlled, flow-through gas-exchange fluorescence measurement systems (GFS-3000, Walz, Germany; LI6400, LI-COR, USA). For mosses the living apical parts (~0.5 to 1 cm) were harvested right before the measurement and placed on a custom-made cuvette. For vascular plants, leaves, or in the case of shrubs, segments of branches were enclosed within the cuvette without disturbing the connection to the rooting system. Net photosynthesis rate (A, µmol m-2 g-1 s-1) was measured at 1500, 250, 35, and 0 µmol m-2 s-1 photosynthetic photon flux density (PPFD). The cuvette conditions were kept constant (temperature 20°C, CO2 concentration 400 ppm, flow rate 500, impeller in level 5). Relative humidity (Rh) of incoming air was set to 40% for vascular plants and 60% for mosses; for mosses this setting retained the cuvette Rh at around 80%. The setting enabled mosses to remain moist to ensure photosynthesis but protected the device from excess moisture. The data was collected to find out the impact of long-term WLD on functional traits of vascular plants and mosses, and how this impact is modulated by nutrient status (rich fen, poor fen, bog). We first assess (i) how peatland species differ in their traits and their intraspecific trait variability, to quantify (ii) how WLD impacts community level traits at different peatland sites.

The data were collected from an experiment using phytoplankton cultures (Apocalathium malmogiense and Rhodomonas marina). The aim of the experiment was to study carbon cycling among phytoplankton and bacteria, and the effects on the dissolved organic matter (DOM) pool. Measured variables include phytoplankton and bacterial abundance, primary production, bacterial production and respiration, 14C-transfer from phytoplankton to DOM and bacteria, concentrations of particulate and dissolved organic carbon, nitrate, phosphate and chlorophyll a, and optical characteristics of dissolved organic matter. The experiment was conducted at Tvärminne Zoological Station, Hanko, Finland with non-axenic unialgal phytoplankton cultures and bacteria originating from the Baltic Sea. The experiment was conducted between Dec. 2017 and Apr. 2018. The experiment consisted of two parts, the DOM release experiment (part 1) and the DOM consumption experiment (part 2). Separate triplicate batch cultures of both phytoplankton species were grown for each experiment. In the DOM release experiment the cultures were grown for over 4 months and three day-long incubations (key point incubations, KPI's) were initiated on three occasions; the first KPI at early exponential growth phase and the second and third KPI's when the phytoplankton had grown more abundant. During each KPI and aliquot of the culture was inoculated with freshly collected sea water bacteria, and bacterial community composition was measured. This aliquot was then divided into two further aliquots; one was incubated with radioisotopes for productivity (primary and bacterial production) and 14C-flow analyses (production line) and one filtered through 0.8 µm for analysis of DOM optical properties. During the KPI's measurements were taken at 0, 4, 8 and 12 h. Nutrient concentrations (measured from non-filtered and 0.8 µm filtered samples) and concentration of dissolved organic carbon were measured only at 0 and 12 h. Concentrations of particulate organic carbon and nitrogen and chlorophyll a were measured only once for each KPI at the beginning of the incubation. In the DOM consumption experiments the cultures were grown to high abundance, after which the phytoplankton and most of the bacteria were filtered out. The filtrate was then inoculated with freshly collected sea water bacteria, after which it was incubated for 7 days. Bacterial abundance, production, respiration, and community composition, and concentration and optical properties of DOM were measured daily. The experimental design is explained in figure 1 of the associated publication.

We estimated plant community composition as the projection cover of each vascular plant and moss species. We measured the following vascular plant functional traits: plant height, leaf size (LS), specific leaf area (SLA) and leaf carbon (C) and nitrogen (N) contents from the most common species in each site. We measured the following Sphagnum traits: stand density (number of shoots cm-2), capitulum width (cap_width, mm) and dry weight (cap_dw, mg), fascicle density (number cm-1), capitulum dry matter content (CDMC, mg g-1), capitulum water content (cap_wc, g g-1) and capitulum C and N contents and C:N ratio. The data was collected from 47 northern peatlands located in land uplift regions in Finland, Sweden and Russia: Sävar on the west coast of Bothnian Bay (63o50'N, 20o40'E, Sweden), Siikajoki (64°45' N, 24°43', Finland) and Hailuoto island (65°07' N, 24°71' E, Finland) on the east coast of Bothnian Bay, and Belomorsk-Virma (63°90' N, 36°50' E, Russia) on the coast of the White Sea. The data was collected from the different areas as follows: Siikajoki sites were sampled in August 2016, Sävar sites at the end of June 2017, Hailuoto sites during July 2017 and Belomorsk sites at the end of August 2017. We determined the plant community composition by visually estimating the projection cover of each species separately for field (vascular plants) and moss layer using the scale 0.1%, 0.25%, 0.5%, 1%, 2%, 3%, etc. There were fifteen 50 x 50 cm plots in each peatland at Siikajoki and Belomorsk-Virma, and 10 at Sävar and Hailuoto. The sample plots were located five meters apart along a transect starting from the generally treeless peatland margin and heading towards the peatland center. Plant traits were measured as follows: To measure SLA (i.e., the one-sided area of a fresh leaf divided by its oven-dry mass, cm2 g-1), the freshly picked leaf or a sample of 3 leaves in case of shrubs with small leaves was pressed flat between a board and a glass and a standardized photo was taken. The leaf size (LS, cm2) was analysed from the photos with ImageJ. The leaf samples were stored in paper bags and dried at 60°C for a minimum of 48h. The dried samples were weighed, and SLA calculated. The SLA samples were used for carbon (C) and nitrogen (N) content analysis. Leaves from each species from each site were pooled into one sample, which was milled (Retsch MM301 mill) and analyzed for C and N concentrations and for C:N ration on a CHNS–O Elemental analyzer (EA1110) (University of Oulu). Sphagnum moss samples for trait measurements were collected with a corer (7 cm diameter, area 38 cm2, height at least 8 cm) to maintain the natural density of the stand. Stand density was measured as the number of mosses in the sample. From ten individuals we measured the width of the capitula and counted the number of fascicles from a five cm segment below capitulum. We separated the ten moss individuals into capitulum and stem (5 cm below capitula) wetted them and allowed to dry on top of tissue paper for 2 min before weighing them for water filled fresh weight. Samples were placed on paper bags and dried at 60 °C for at least 48h after which the dry mass of capitula and stems were measured. CDMC and cap_wc were calculated from the fresh and dry weight. We used the capitula samples for analyses of C and N concentrations and for C:N ratio, and treated them similarly to vascular plant samples. The data was collected to find out how functional diversity and trait composition of vascular plant and Sphagnum moss communities develops during peatland succession across land uplift regions.

Within the setup of a long‐term irrigation experiment in a Scots pine (Pinus sylvestris) forest at Pfynwald in the inner-Alpine Swiss Rhone valley, ecophysiological data were recorded from permanently irrigated trees, from trees cut off the irrigation after 11 years, and non-treated control trees. The data sets include continuous stem radius changes (automated point dendrometer at breast height), tree stem sap flow (Granier-type sap flow sensors at breast height), air temperature and humidity, vapour pressure deficit, net solar radiation, precipitation (tipping bucket), and volumetric soil water content (TDR and HS-sensors). The meteorological data were measured 2 m above the canopy in about 13 m height on top of a scaffold. The soil water sensors covered soil depth of up to 80 cm. Data resolution is 1 hour or higher and covers the years 2011-2017. Data as used and published in Zweifel, et al. (2020), Determinants of legacy effects in pine trees ‐ implications from an irrigation‐stop experiment. New Phytol. doi:10.1111/nph.16582

In an enclosure experiment, we employed two levels of inorganic NP ratios (10 and 5) for three distinct plankton communities collected along the coast of central Chile (33ºS). Each combination of community and NP level was replicated three times. The experiment lasted 12 days, and the data set include inorganic nutrients (NO3, PO4, DSi), particular organic carbon (POC), nitrogen (PON) and phosphorus (POP), Chlorophyll a, a range of fluorescence based measurements such as photochemical efficiency (Fv/Fm) and community data. The primary effect of the NP treatment was related to different concentrations of NO3, which directly influenced the biomass of phytoplankton. Additionally, low inorganic NP ratio reduced the seston NP and Chl a-C ratios, and there were some effects on the plankton community composition, e.g. benefitting Synechococcus spp in some communities.

Data on morphological and biochemical traits of the bladderwrack Fucus vesiculosus were obtained from individuals simultaneously collected in September 2011 in 20 stations along the Baltic Sea and 4 stations in the North Sea. The individuals included in the analysis were collected at 0.5-1.0 m depth. Frond length, frond width, stipe width and number of fronds were directly determined in the field. All collected individuals were transported to the laboratory in cooler boxes at temperatures below 5 °C, then frozen at -20 °C within 12 h, and shipped to the GEOMAR-Helmholtz Centre for Ocean Research Kiel (Germany) on dry ice. Measurements of chlorophyll a and fucoxanthin in surface and tissue extracts, mannitol, phlorotannins and carbon:nitrogen ratio were performed in the laboratory (see further methodological details in the related article). The relative palatability of the algal material collected in all 24 stations was determined in palatability assays, using reconstituted algal pellets and the pan-Baltic grazer Idotea balthica. In addition to the trait information, environmental data on sea surface salinity, sea surface summer temperature, photosynthetically active radiation (PAR), wave exposure and total nitrogen have been obtained from the Swedish Meteorological and Hydrological Institute (SMHI) or local monitoring services.

The presented datasets contain * chamber CO2 measurement and leaf area data of years 2012-2014 used in fitting the non-linear model * chamber CO2 measurement and leaf area data of year 2015 used for model validation * data for flux reconstruction using the model

Computer models are necessary for understanding and predicting marine ice sheet behaviour. However, there is uncertainty over implementation of physical processes at the ice base, both for grounded and floating glacial ice. Here we implement several sliding relations in a marine ice sheet flow-line model accounting for all stress components and demonstrate that model resolution requirements are strongly dependent on both the choice of basal sliding relation and the spatial distribution of ice shelf basal melting.Sliding relations that reduce the magnitude of the step change in basal drag from grounded ice to floating ice (where basal drag is set to zero) show reduced dependence on resolution compared to a commonly used relation, in which basal drag is purely a power law function of basal ice velocity. Sliding relations in which basal drag goes smoothly to zero as the grounding line is approached from inland (due to a physically motivated incorporation of effective pressure at the bed) provide further reduction in resolution dependence.A similar issue is found with the imposition of basal melt under the floating part of the ice shelf: melt parameterisations that reduce the abruptness of change in basal melting from grounded ice (where basal melt is set to zero) to floating ice provide improved convergence with resolution compared to parameterisations in which high melt occurs adjacent to the grounding line.Thus physical processes, such as sub-glacial outflow (which could cause high melt near the grounding line), impact on capability to simulate marine ice sheets. If there exists an abrupt change across the grounding line in either basal drag or basal melting, then high resolution will be required to solve the problem. However, the plausible combination of a physical dependency of basal drag on effective pressure, and the possibility of low ice shelf basal melt rates next to the grounding line, may mean that some marine ice sheet systems can be reliably simulated at a coarser resolution than currently thought necessary.

In late 2014, a large, oxygen-rich salt water inflow entered the Baltic Sea and caused considerable changes in deep water oxygen concentrations. We studied the effects of the inflow on the concentration patterns of two greenhouse gases, methane and nitrous oxide, during the following year (2015) in the water column of the Gotland Basin. In the eastern basin, methane which had previously accumulated in the deep waters was largely removed during the year. Here, volume-weighted mean concentration below 70 m decreased from 108 nM in March to 16.3 nM over a period of 141 days (0.65 nM d−1), predominantly due to oxidation (up to 79 %) following turbulent mixing with the oxygen-rich inflow. In contrast nitrous oxide, which was previously absent from deep waters, accumulated in deep waters due to enhanced nitrification following the inflow. Volume-weighted mean concentration of nitrous oxide below 70 m increased from 11.8 nM in March to 24.4 nM in 141 days (0.09 nM d−1). A transient extreme accumulation of nitrous oxide (877 nM) was observed in the deep waters of the Eastern Gotland Basin towards the end of 2015, when deep waters turned anoxic again, sedimentary denitrification was induced and methane was reintroduced to the bottom waters. The Western Gotland Basin gas biogeochemistry was not affected by the inflow.

Iron (Fe) plays a key role in sedimentary diagenetic processes in coastal systems, participating in various redox reactions and influencing the burial of organic carbon. Large amounts of Fe enter the marine environment from boreal river catchments associated with dissolved organic matter (DOM) and as colloidal Fe oxyhydroxides, principally ferrihydrite. However, the fate of this Fe pool in estuarine sediments has not been extensively studied. Here we show that flocculation processes along a salinity gradient in an estuary of the northern Baltic Sea efficiently transfer Fe and OM from the dissolved phase into particulate material that accumulates in the sediments. Flocculation of Fe and OM is partially decoupled. This is likely due to the presence of discrete colloidal ferrihydrite in the freshwater Fe pool, which responds differently from DOM to estuarine mixing. Further decoupling of Fe from OM occurs during sedimentation. While we observe a clear decline with distance offshore in the proportion of terrestrial material in the sedimentary particulate organic matter (POM) pool, the distribution of flocculated Fe in sediments is modulated by focusing effects. Labile Fe phases are most abundant at a deep site in the inner basin of the estuary, consistent with input from flocculation and subsequent focusing. The majority of the labile Fe pool is present as Fe (II), including both acid-volatile sulfur (AVS)-bound Fe and unsulfidized phases. The ubiquitous presence of unsulfidized Fe (II) throughout the sediment column suggests Fe (II)-OM complexes derived from reduction of flocculated Fe (III)-OM, while other Fe (II) phases are likely derived from the reduction of flocculated ferrihydrite. Depth-integrated rates of Fe (II) accumulation (AVS-Fe + unsulfidized Fe (II) + pyrite) for the period 1970-2015 are greater in the inner basin of the estuary with respect to a site further offshore, confirming higher rates of Fe reduction in near-shore areas. Mössbauer 57Fe spectroscopy shows that refractory Fe is composed largely of superparamagnetic Fe (III), high-spin Fe (II) in silicates, and, at one station, also oxide minerals derived from past industrial activities. Our results highlight that the cycling of Fe in boreal estuarine environments is complex, and that the partial decoupling of Fe from OM during flocculation and sedimentation is key to understanding the role of Fe in sedimentary diagenetic processes in coastal areas. Note that data for Figure 7 (Mössbauer profiles) and the PROFILE outputs presented in Figure 8 are not included in this dataset.