ALBERT

Description: We present an SiF4 separation line, coupled to a laser fluorination system, which allows for an efficient combined silica d18O and d30Si analysis (50 min per sample). The required sample weight of 1.5-2.0 mg allows for high-resolution isotope studies on biogenic opal. Besides analytical tests, the new instrumentation set-up was used to analyse two marine diatom fractions (〉63 µm, 10-20 µm) with different diatom species compositions extracted from a Bølling/Allerød-Holocene core section [MD01-2416, North-West (NW) Pacific] to evaluate the palaeoceanographic significance of the diatom isotopic signals and to address isotopic effects related to contamination and species-related isotope effects (vital and environmental effects). While d30Si offsets between the two fractions were not discernible, supporting the absence of species-related silicon isotope effects, systematic offsets occur between the d18O records. Although small, these offsets point to species-related isotope effects, as bias by contamination can be discarded. The new records strengthen the palaeoceanographic history during the last deglaciation in the NW Pacific characterized by a sequence of events with varying surface water structure and biological productivity. With such palaeoceanographic evolution it becomes unlikely that the observed systematic d18O offsets signal seasonal temperature variability. This calls for reconsideration of vital effects, generally excluded to affect d18O measurements.

Description: The glacial-to-Holocene evolution of subarctic Pacific surface water stratification and silicic acid (Si) dynamics is investigated based on new combined diatom oxygen (d18Odiat) and silicon (d30Sidiat) isotope records, along with new biogenic opal, subsurface foraminiferal d18O, alkenone-based sea surface temperature, sea ice, diatom, and core logging data from the NE Pacific. Our results suggest that d18Odiat values are primarily influenced by changes in freshwater discharge from the Cordilleran Ice Sheet (CIS), while corresponding d30Sidiat are primarily influenced by changes in Si supply to surface waters. Our data indicate enhanced glacial to mid Heinrich Stadial 1 (HS1) NE Pacific surface water stratification, generally limiting the Si supply to surface waters. However, we suggest that an increase in Si supply during early HS1, when surface waters were still stratified, is linked to increased North Pacific Intermediate Water formation. The coincidence between fresh surface waters during HS1 and enhanced ice-rafted debris sedimentation in the North Atlantic indicates a close link between CIS and Laurentide Ice Sheet dynamics and a dominant atmospheric control on CIS deglaciation. The Bølling/Allerød (B/A) is characterized by destratification in the subarctic Pacific and an increased supply of saline, Si-rich waters to surface waters. This change toward increased convection occurred prior to the Bølling warming and is likely triggered by a switch to sea ice-free conditions during late HS1. Our results furthermore indicate a decreased efficiency of the biological pump during late HS1 and the B/A (possibly also the Younger Dryas), suggesting that the subarctic Pacific has then been a source region of atmospheric CO2.

Description: Reduced surface-deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface-subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring-summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall-winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink.

Description: This vcf file is generated from genomic data of three-spined sticklebacks from Kiel (KIE), Germany and Nynäshamn (NYN), Sweden. The individuals from Kiel are S3, S4, S19, S20, S33, S34, S47, S48, S49, S50, S63, S64, S77, S78, S89, S90. The individuals from NYN are S5, S6, S21, S22, S35, S36, S37, S38, S51, S52, S65, S66, S79, S80, S85, S86. It contains high quality biallelic positions (GQ=20) and is filtered for minor allele frequencies of maf = 0.05, allows 40 % of missing data (13 individuals) and a read depth of 〉=5. Further this vcf file is subset to the inducible differentially methylated sites (DMS) (198sites) in decreasing PSU (_6PSU) with 5 kilobases (kb) before and after DMS. With this file further calculations were performed to estimate the genetic differentiation (i.e. Fst) between the different populations (see manuscript indicated below).

Description: This vcf file is generated from genomic data of three-spined sticklebacks from Kiel (KIE) and Sylt (SYL), Germany. The individuals from Kiel are S3, S4, S19, S20, S33, S34, S47, S48, S49, S50, S63, S64, S77, S78, S89, S90. The individuals from SYL are S9, S10, S17, S18, S31, S32, S45, S46, S59, S60, S61, S62, S73, S74, S87, S88. It contains high quality biallelic positions (GQ=20) and is filtered for minor allele frequencies of maf = 0.05, allows 40 % of missing data (13 individuals) and a read depth of 〉=5. Further this vcf file is subset to the inducible differentially methylated sites (DMS) (148sites) in increasing PSU (_33PSU) with 5 kilobases (kb) before and after DMS. With this file further calculations were performed to estimate the genetic differentiation (i.e. Fst) between the different populations (see manuscript indicated below).

Description: Little is known about the climate evolution on the Kamchatka Peninsula during the last glacial?interglacial transition as existing climate records do not reach beyond 12 ka BP. In this study, a summer temperature record for the past 20 kyr is presented. Branched glycerol dialkyl glycerol tetraethers, terrigenous biomarkers suitable for continental air temperature reconstructions, were analyzed in a sediment core from the western continental margin off Kamchatka in the marginal northwest Pacific (NW Pacific). The record suggests that summer temperatures on Kamchatka during the Last Glacial Maximum (LGM) equaled modern temperatures. We suggest that strong southerly winds associated with a pronounced North Pacific High pressure system over the subarctic NW Pacific accounted for the warm conditions. A comparison with an Earth system model reveals discrepancies between model and proxy-based reconstructions for the LGM temperature and atmospheric circulation in the NW Pacific realm. The deglacial temperature development is characterized by abrupt millennial-scale temperature oscillations. The Bølling?Allerød warm phase and the Younger Dryas cold spell are pronounced events, suggesting a connection to North Atlantic climate variability.

Description: It has been proposed that North Pacific sea surface temperature (SST) evolution was intimately linked to North Atlantic climate oscillations during the last glacial-interglacial transition. However, during the early deglaciation and the Last Glacial Maximum, the SST development in the subarctic northwest Pacific and the Bering Sea is poorly constrained as most existing deglacial SST records are based on alkenone paleothermometry, which is limited prior to 15 ka B.P. in the subarctic North Pacific realm. By applying the TEXL86 temperature proxy we obtain glacial-Holocene-SST records for the marginal northwest Pacific and the Western Bering Sea. Our TEXL86-based records and existing alkenone data suggest that during the past 15.5 ka, SSTs in the northwest Pacific and the Western Bering Sea closely followed millennial-scale climate fluctuations known from Greenland ice cores, indicating rapid atmospheric teleconnections with abrupt climate changes in the North Atlantic. Our SST reconstructions indicate that in the Western Bering Sea SSTs drop significantly during Heinrich Stadial 1 (HS1), similar to the known North Atlantic climate history. In contrast, progressively rising SST in the northwest Pacific is different to the North Atlantic climate development during HS1. Similarities between the northwest Pacific SST and climate records from the Gulf of Alaska point to a stronger influence of Alaskan Stream waters connecting the eastern and western basin of the North Pacific during this time. During the Holocene, dissimilar climate trends point to reduced influence of the Alaskan Stream in the northwest Pacific.

Description: This data set contains four time series of particulate and dissolved soil nitrogen measurements from the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. 1. Total nitrogen from solid phase: Stratified soil sampling was performed every two years since before sowing in April 2002 and was repeated in April 2004, 2006 and 2008 to a depth of 30 cm segmented to a depth resolution of 5 cm giving six depth subsamples per core. In 2002 five samples per plot were taken and analyzed independently. Averaged values per depth layer are reported. In later years, three samples per plot were taken, pooled in the field, and measured as a combined sample. Sampling locations were less than 30 cm apart from sampling locations in other years. All soil samples were passed through a sieve with a mesh size of 2 mm in 2002. In later years samples were further sieved to 1 mm. No additional mineral particles were removed by this procedure. Total nitrogen concentration was analyzed on ball-milled subsamples (time 4 min, frequency 30 s-1) by an elemental analyzer at 1150°C (Elementaranalysator vario Max CN; Elementar Analysensysteme GmbH, Hanau, Germany). 2. Total nitrogen from solid phase (high intensity sampling): In block 2 of the Jena Experiment, soil samples were taken to a depth of 1m (segmented to a depth resolution of 5 cm giving 20 depth subsamples per core) with three replicates per block ever 5 years starting before sowing in April 2002. Samples were processed as for the more frequent sampling but were always analyzed independently and never pooled. 3. Mineral nitrogen from KCl extractions: Five soil cores (diameter 0.01 m) were taken at a depth of 0 to 0.15 m (and between 2002 and 2004 also at a depth of 0.15 to 0.3 m) of the mineral soil from each of the experimental plots at various times over the years. In addition also plots of the management experiment, that altered mowing frequency and fertilized subplots (see further details below) were sampled in some later years. Samples of the soil cores per plot (subplots in case of the management experiment) were pooled during each sampling campaign. NO3‐N and NH4‐N concentrations were determined by extraction of soil samples with 1 M KCl solution and were measured in the soil extract with a Continuous Flow Analyzer (CFA, 2003–2005: Skalar, Breda, Netherlands; 2006–2007: AutoAnalyzer, Seal, Burgess Hill, United Kingdom). 4. Dissolved nitrogen in soil solution: Glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1–1.6 µm (UMS GmbH, Munich, Germany) were installed in April 2002 in depths of 10, 20, 30 and 60 cm to collect soil solution. The sampling bottles were continuously evacuated to a negative pressure between 50 and 350 mbar, such that the suction pressure was about 50 mbar above the actual soil water tension. Thus, only the soil leachate was collected. Cumulative soil solution was sampled biweekly and analyzed for nitrate (NO3-), ammonium (NH4+) and total dissolved nitrogen concentrations with a continuous flow analyzer (CFA, Skalar, Breda, The Netherlands). Nitrate was analyzed photometrically after reduction to NO2- and reaction with sulfanilamide and naphthylethylenediamine-dihydrochloride to an azo-dye. Our NO3- concentrations contained an unknown contribution of NO2- that is expected to be small. Simultaneously to the NO3- analysis, NH4+ was determined photometrically as 5-aminosalicylate after a modified Berthelot reaction. The detection limits of NO3- and NH4+ were 0.02 and 0.03 mg N L-1, respectively. Total dissolved N in soil solution was analyzed by oxidation with K2S2O8 followed by reduction to NO2- as described above for NO3-. Dissolved organic N (DON) concentrations in soil solution were calculated as the difference between TDN and the sum of mineral N (NO3- + NH4+).

Description: This data set contains information about the functional structure (overall biomass; abundance of consumers: in different habitat strata; of different food resource specialization, feeding strategies and aerial mobility) of aboveground consumers (herbivores, carnivores, omnivores and decomposers) per plots from a grassland plant diversity experiment (the Jena Experiment; Roscher et al. 2004). The experiment was established in 2002, and consists of 80 grassland plots. Plots vary in plant species richness (1, 2, 4, 8, 16, or 60 species). All plots are mown twice per year, and weeded three times per year to maintain the experimental diversity gradient. We collected ground-associated arthropods over 125 days from May until September 2010 using two pitfall traps of 4.5 cm diameter per plot. During the sampling periods, the field traps were filled with 3% formalin and after emptying the traps, animals were stored in 70% ethanol. Vegetation-associated arthropods were collected by suction sampling in early June and August (during the peak biomass of the plant communities) using a modified commercial vacuum cleaner. We randomly chose three subplots of 0.75 m x 0.75 m within each plot, covered them with a gauze cage of the same size, and sampled arthropods by vacuuming the inside of the cages until we spotted no arthropods anymore. Samples were identified to species level, except for Hymenoptera, which were identified to the level of family or subfamily. We pooled data of all sampling campaigns in 2010 and standardized the resulting abundances between zero and one, separately for pitfall and suction sampling to account for different sampling intensities between the two methods (Hertzog et al. 2016). We focused on species that we sampled more than once during the whole vegetation period.

Description: This collection contains measurements of abundance and diversity of different groups of aboveground invertebrates sampled on the plots of the different sub-experiments at the field site of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. The following series of datasets are contained in this collection: 1. Measurements of ant abundance (number of individuals attracted to baits) and ant occurrence (binary data) in the Main Experiment in 2006 and 2013. Ants where sampled using two types of baited traps receiving ~10g of Tuna or ~10g of honey/Sucrose. After 30min the occurrence (presence = 1 / absence = 0) and abundance (number) of ants at the two types of baits was recorded and pooled per plot.