Kathryn Schreiner Byron Steinman 20250709 csv Sciencebase U.S. Geological Survey Data Release Kathryn Schreiner (https://orcid.org/0000-0002-7600-5006), University of Minnesota Byron Steinman (https://orcid.org/0000-0003-2256-1856), University of Minnesota https://doi.org/10.5066/P1RRO9AA This dataset contains geochemical, isotopic, and biomarker data derived from sediment cores collected in Siskiwit Bay, Lake Superior, Wisconsin, USA. The dataset supports the reconstruction of historical phytoplankton communities, including cyanobacterial blooms, and environmental conditions over the past ~5,400 years. Measurements include carotenoid and chlorophyll pigments (via high-performance liquid chromatography), stable carbon isotopes, total carbon and nitrogen content (via elemental analyzer isotope ratio mass spectrometry), radiocarbon and lead-210 dating, loss-on-ignition, and X-ray fluorescence elemental profiles. These data reveal historical shifts in phytoplankton dominance, sand layer deposition events, and transitions between cyanobacteria- and diatom-dominated community. The data were collected to reconstruct historical environmental conditions and phytoplankton community dynamics, with a focus on identifying the timing and frequency of past cyanobacterial blooms in Siskiwit Bay, Lake Superior. These reconstructions provide context for recent observations of cyanobacteria blooms and help distinguish natural variability from potential anthropogenic influences. The dataset can be used by future researchers to study long-term ecosystem changes, validate paleoclimate models, assess historical nutrient dynamics, and inform lake management and conservation strategies 20210928 date the field visit was coducted to collected the Siskiwit Bay cores Complete None planned Siskiwit Bay, WI -91.13966 -91.08799 46.88472 46.85420 ISO 19115 Topic Category inlandWaters environment None Paleolimnology Cyanobacteria Sediment cores Last millennium Environmental reconstruction USGS Thesaurus limnology phytoplankton freshwater ecosystems sedimentology algae USGS Metadata Identifier USGS:683df569d4be0234870fca79 Common geographic areas Wisconsin Lake Superior Integrated Taxonomic Information System Cyanobacteriota Phylum Cyanobacteriota Oren Cyanobacteria No data access constraints. Please see 'Distribution Info' for details. No data use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Kathryn Schreiner University of Minnesota mailing

126 HCAMS

Duluth MN 55812 USA 218.726.8680 kschrein@d.umn.edu This work was Midwest Climate Adaptation Science Center The age model data were processed using BACON program with the PLUM package (Aquino-López et al., 2018). BACON and PLUM are Open source age model data processing software commonly used to produce age models for geological archives. rBACON (https://cran.r-project.org/web/packages/rbacon/vignettes/rbacon.html) See methods descriptions for greater detail. Methods of instrument calibrations, reproducibility assessments, and spot checks were all used to ensure accuracy in the data. All values fall within expected ranges and data have been spot checked to rule out any inconsistencies. All data generated were reported and spot checked for completeness. These data were produced in the fixed geographic range of Siskiwit Bay. David Harris William R. Horwáth Chris van Kessel 20011101 publication Soil Science Society of America Journal vol. 10.2136/sssaj2001.1853, issue 6 https://acsess.onlinelibrary.wiley.com/doi/10.2136/sssaj2001.1853 Wiley ppg. 1853-1856 https://doi.org/10.2136/sssaj2001.1853 Digital and/or Hardcopy 2001 publication date Harris et al., 2001 bulk element and isotope analysis protocol Walter E. Dean 1974 publication Journal of Sedimentary Petrology, 44, 242-248 https://doi.org/10.1306/74d729d2-2b21-11d7-8648000102c1865d Digital and/or Hardcopy 1974 publication date Dean, 1974 Loss on Ignition protocol Mark B. Abbott Thomas W. Stafford 1996 publication Quaternary Research vol. S0033589400024819, issue 3 https://www.cambridge.org/core/product/identifier/S0033589400024819/type/journal_article Cambridge University Press (CUP) ppg. 300-311 https://doi.org/10.1006/qres.1996.0031 Digital and/or Hardcopy 1996 publication date Abbott & Stafford, 1996 geochronology processing protocol Marco A. Aquino-López Maarten Blaauw J. Andrés Christen Nicole K. Sanderson 20180605 publication Journal of Agricultural, Biological and Environmental Statistics vol. 328, issue 3 http://link.springer.com/10.1007/s13253-018-0328-7 Springer Science and Business Media LLC ppg. 317-333 https://doi.org/10.1007/s13253-018-0328-7 Digital and/or Hardcopy 2018 publication date Aquino-López et al., 2018 age model data process protocol Sample Collection and Processing: To investigate the existence of historical cyanobacterial blooms in Lake Superior’s Western Arm, surface water samples were collected in multiple places around Siskiwit Lake on June 8th, 2021, during a cyanobacteria bloom. Surface water grab samples were taken from the Siskiwit Lake Boat Launch, Siskiwit Lake Campground, and both the Left and Right sides of the Dock. Three sediment cores were collected from the same location in Siskiwit Bay on September 28th, 2021, using an Aquatic Instruments Hammer Corer with 2-5/8 in diameter polycarbonate core barrels. Out of these three cores, one (88 cm) would be used for an XRF analysis, another (126 cm) for 210Pb and 14C dating, and finally one for bulk elemental and isotopic concentrations, pigment analysis and 14C dating. Sediment packages for coring were previously identified via CHIRP data collection on September 15th, 2021, with a SB-424 Full Spectrum Sub-Bottom Tow Vehicle (EdgeTech Discover Sub-Bottom 4.09) aboard the R/V Kingfisher. The three long cores ranged from 65 cm to 126 cm in length. One of these cores was analyzed by x-radiograph analysis, while the two others were visually inspected; all were determined to have an undisturbed sediment-water interface. Using a tray fitted to the top of the core barrel and a spatula, two Siskiwit Bay sediment cores were extruded into 1 cm samples down the entire core length (65 cm and 126 cm, respectively) and stored in 24 oz polyethylene Nasco WHIRL-PAKs. Between each centimeter section, the extruder tray and spatula were wiped dry with paper towel to minimize contamination between samples. All extruded samples were frozen at -20°C within 12 hours of collection and then lyophilized to dryness with a LABCONCO Freezone-6 System. After lyophilization, samples were inspected visually for terrestrial organic matter, such as leaves and sticks, and these were removed for carbon-14 (14C) dating. Samples were ground and homogenized with a mortar and pestle, weighed, and kept in pre-combusted glass scintillation vials, and stored at -20°C until further processing and analysis. The third core (89 cm) from Siskiwit Bay was split longitudinally down the core barrel with one half archived for X-ray fluorescence (XRF) analysis. 2021 One of the three core samples was used to run a bulk element and isotope analysis following protocol in Harris et al., 2001. Harris et al., 2001 2021 A loss of ignition test was conducted following protocol from Dean, 1974 to determine the organic material composition of the sample. Dean, 1974 2021 Geochronology: The core was then aged using geochronology methods found in Abbott & Stafford, 1996 for 210Pb and 14C dating, with the age model data being processed using BACON program with the PLUM package from Aquino-López et al., 2018. Abbott & Stafford, 1996 Aquino-López et al., 2018 2021 Pigment Analysis: Pigments were extracted from approximately 2 g dry weight samples of freeze-dried sediment or ground water filters with 5 mL of optima-grade acetone. Samples were suspended in acetone and then sonicated for 1 minute to break cell walls. Then, samples were stored at -20°C for 12 to 16 hours, centrifuged at 2,000 rpm for 5 minutes (G force of 454), and filtered using 0.22 μm NYLON 25 mm syringe filters to separate solid and liquid phases. Dissolved pigments were then blown down to dryness and reconstituted in 200 μL of Optima-grade acetone with 0.500 mg/L trans-β-Apo-8’-carotenal internal standard (Sigma Aldrich) prior to analysis on a ThermoScientific Dionex UltiMate 3000 UHPLC outfitted with photodiode array detector and fluorescence detector. Each injected sample was separated into individual pigments using the two mobile phases, (A) 70:30 (v:v) Methanol:Tetrabutylammonium acetate (TbAA) and (B) 100% Optima-grade Methanol, at a flowrate of 0.200 mL/min through an Agilent - Zorbax Eclipse Plus C8 HPLC column (2.1 x 100 mm, 95Å, 1.8-μm) and a VanGuard - Acquity UPLC BEH C8 HPLC guard column (2.1 x 5 mm, 1.7-μm). Each injection’s flow gradient started with 95% mobile phase A and 5% B that lasted 11.5 minutes, then ramped up to 5% A and 95% B over the course of 15 minutes, held there for another 11.5 minutes, until it ramped back down to 95% A and 5%B, where it was then held for the remaining 6 minutes. The resulting elution order and method of identification of each pigment can be seen in Table 4. Pigment peak identification and quantification within sediment samples were performed through comparison to the internal standard and standard pigments (DHI Laboratories, Denmark). All actions were performed in dark or dim-light to reduce the amount of pigment degradation. Pheophytin-a, a degradation product of chlorophyll-a, when used in summary with chlorophyll-a can be referred to as the sum of chlorophyll-a at the time of deposition. Pheophytin-a was ratioed to this past sum of chlorophyll-a to produce a relative percentage of chlorophyll-a degradation since deposition. 2022 X-ray fluorescence: X-ray fluorescence analysis was performed on the split core at a 0.2-cm radiographic resolution and a 60-second dwell time. Elemental measurements were performed on a ITRAX Core Scanner (COX Analytical Systems, Molndal, Sweden) located at the Large Lakes Observatory, University of Minnesota, Duluth. The split-cores were wrapped with 4 μm Ultralene film for preservation and, prior to measurement, the surface sediment was smoothed to reduce the roughness of the surface. Scans were conducted at a voltage of 10 kV, yielding count intensities for elements Al, Si, K, Ti, and Pb. 2022 EA_LOI_Output.csv Tabular data output results from the Elemental Analysis and Loss of Ignition tests. Producer Defined Depth Depth in core. Measurement in cm is the bottom of the extruded section (ex: depth = 1 is the extruded section 0-1cm). Producer Defined << empty cell >> No Data Producer defined 1 89 centimeter Cal Year BP Calendar year before present representing years counted backward from the year 1950 Producer Defined << empty cell >> No Data Producer defined -68.6 5333.8 years Linear Sed Rate sedimentation rate in cm per year Producer Defined << empty cell >> No Data Producer defined -0.015 0.455 cm/yr Sediment Weight mass of the sample Producer Defined << empty cell >> No Data Producer defined 4.181 74.104 grams Dry Bulk Density density of the sample (Sediment Weight / Volume). Volume for each sample = 3.1416*1*(6.6675/2)^2 Producer Defined << empty cell >> No Data Producer defined 0.1198 2.1224 g / cm^3 Total Sed Flux mass flux of sediment (Dry Bulk Density * Linear Sed Rate) Producer Defined << empty cell >> No Data Producer defined 0.0062 0.0601 g / [cm^2 * yr] Organic Matter weight percent of organic matter per dry sediment determined by Loss on Ignition (LOI) Producer Defined << empty cell >> No Data Producer defined 0.616 7.487 weight percent Organic Flux weight percent of organic matter * total sediment flux / 100 Producer Defined << empty cell >> No Data Producer defined 7e-05 0.00436 g / [cm^2 * yr] CaCO3 percent CaCO3 by weight Producer Defined << empty cell >> No Data Producer defined 0.676 4.04 weight percent CaCO3 Flux weight percent of CaCO3 * total sediment flux / 100 Producer Defined << empty cell >> No Data Producer defined 0.0 0.002 g / [cm^2 * yr] TOC percent total organic carbon by weight Producer Defined << empty cell >> No Data Producer defined 0.109 2.332 weight percent TOC Flux weight percent of TOC * total sediment flux / 100 Producer Defined << empty cell >> No Data Producer defined 1.51e-05 0.00139 g / [cm^2 * yr] N percent nitrogen by weight Producer Defined << empty cell >> No Data Producer defined 0.04 0.26 weight percent TN Flux weight percent of N * total sediment flux / 100 Producer Defined << empty cell >> No Data Producer defined 3.25e-06 0.000149 g / [cm^2 * yr] Residual 100 - % CaCO3 - % organic matter Producer Defined << empty cell >> No Data Producer defined 88.47 98.71 weight percent Residual Flux weight percent of residual * total sediment flux / 100 Producer Defined << empty cell >> No Data Producer defined 0.006 0.054 g / [cm^2 * yr] Molar TOC/TN molar ratio of total organic carbon to total nitrogen Producer Defined << empty cell >> No Data Producer defined 10.521 15.455 delta13C Carbon stable isotope content in delta units using Vienna PeeDee Belemnite (VPDB) as standard Producer Defined << empty cell >> No Data Producer defined -27.89 -24.45 AgeModel_output.csv Tabular data outputs from age modeling using geochronology methods found in Abbott & Stafford, 1996 for 210Pb and 14C dating. Raw data input files are included as well. Producer Defined depth Depth in sediment profile Producer Defined 0 89 centimeters min 2σ low age Producer Defined -71.0 5234.4 years max 2σ high age Producer Defined -71.0 5491.8 years median median age Producer Defined -71.0 5333.8 years mean mean age Producer Defined -71.0 5341.7 year XRF_output.csv Tabular data generated by the X-ray fluorescence analysis revealing the elemental composition of a sample. Producer Defined Depth depth in core Producer Defined 1 89 centimeters Age Number of years counted backward from the year 1950 Producer Defined -68.6 5333.8 years Al Scanning X-ray fluorescence for aluminum Producer Defined 236.2 1207.4 counts Si Scanning X-ray fluorescence for Silicon Producer Defined 2145.0 13595.0 counts K Scanning X-ray fluorescence for potassium Producer Defined 20129.2 94517.0 counts Ca Scanning X-ray fluorescence for calcium Producer Defined 15610.4 62929.8 counts Ti Scanning X-ray fluorescence for titanium Producer Defined 20462.8 83848.8 counts Mn Scanning X-ray fluorescence for manganese Producer Defined 4034.6 10013.4 counts Fe Scanning X-ray fluorescence for iron Producer Defined 70483.4 228257.2 counts Pb Scanning X-ray fluorescence for lead Producer Defined 0.0 378.2 counts Pb-Cs_raw.csv Tabular data used as inputs in the age modeling. The Pb-210 dating method relies on the radioactive decay of naturally occurring Lead-210 (210Pb) to establish chronologies in sediment cores up to 100-150 years. Cesium-137 (137Cs), an artificial radionuclide with a half-life of 30.17 years, serves as a discrete time marker in sediment cores and is used to validate the age models derived from 210Pb dating. Producer Defined Depth depth in sediment profile Producer Defined 2.0 40.5 centimeters Total 210Pb Total 210Pb expressed as DPM Producer Defined 1.805847729 38.18117932 DPM (decays per minute) Total 210Pb Uncertainty Total 210Pb expressed as DPM 1σ uncertainty Producer Defined 0.232561976 1.459971474 DPM (decays per minute) Supported 210Pb Supported 210Pb expressed as DPM Producer Defined 1.306706642 2.586282109 DPM (decays per minute) Supported 210Pb Uncertainty Supported 210Pb expressed as DPM 1σ uncertainty Producer Defined 0.042048469 0.119174036 DPM (decays per minute) 137Cs 137Cs concentration expressed as DPM Producer Defined << empty cell >> No Data Producer defined -0.027380046 9.149096241 DPM (decays per minute) 137Cs Uncertainty 137Cs concentration expressed as DPM 1σ uncertainty Producer Defined << empty cell >> No Data Producer defined -0.028283588 0.133050813 DPM (decays per minute) 14C_raw.csv Tabular data used as input in the age modeling. Radiocarbon (14C) dating is a method used to estimate the age of carbon-containing materials, particularly those derived from once-living organisms Producer Defined UCIAMS University of California Irvine AMS lab sample number Producer Defined 264669 264678 na Sample name PI assigned sample name Producer Defined Name of the sample indicating the location of where it was collected and a unique code assigned by the researcher. 14C age uncalibrated 14C age Producer Defined 360 4710 years 14C age sig uncalibrated 14C age, 1-sigma range. 1 sigma represents a confidence interval of approximately 68%. Producer Defined 15 20 years Depth cm depth in sediment profile Producer Defined 25.5 89.0 centimeters Calibrated 2sig low Calibrated 14C age 2-sigma low age - IntCal20. 2-sigma low refers the lower bound of the age range that has a 95.4% probability of containing the true age of the sample Producer Defined 318 5325 years Calibrated median calibrated 14C age median age - IntCal20. Producer Defined 421 5379 years Calibrated 2sig hi calibrated 14C age 2-sigma high age - IntCal20. 2-sigma low refers the upper bound of the age range that has a 95.4% probability of containing the true age of the sample Producer Defined 491 5568 years AlgalPigment_output.csv Tabular data outputs from the algal pigment analysis showing the pigment composition of the samples. Producer Defined Depth Depth in core. Measurement in cm is the bottom of the extruded section (ex: depth = 1 is the extruded section 0-1cm). Producer Defined 1.0 126.83 centimeters Fucoxanthin Concentration of pigment compound Fucoxanthin Producer Defined << empty cell >> No Data Producer defined 0.0 1810.0 ng (nanograms) pigment per g (gram) dry sediment Neoxanthin Concentration of pigment compound neoxanthin Producer Defined << empty cell >> No Data Producer defined 1.53 14.7 ng (nanograms) pigment per g (gram) dry sediment Aphanizophyll Concentration of pigment compound aphanizophyll Producer Defined << empty cell >> No Data Producer defined 3.85 49.2 ng (nanograms) pigment per g (gram) dry sediment Violaxanthin Concentration of pigment compound violaxanthin Producer Defined << empty cell >> No Data Producer defined 9.12 122.0 ng (nanograms) pigment per g (gram) dry sediment Myxoxanthophyll Concentration of pigment compound myxoxanthophyll Producer Defined << empty cell >> No Data Producer defined 1.62 115.0 ng (nanograms) pigment per g (gram) dry sediment Diadinoxanthin Concentration of pigment compound diadinoxanthin Producer Defined << empty cell >> No Data Producer defined 4.62 103.0 ng (nanograms) pigment per g (gram) dry sediment Alloxanthin Concentration of pigment compound alloxanthin Producer Defined << empty cell >> No Data Producer defined 4.92 177.0 ng (nanograms) pigment per g (gram) dry sediment Diatoxanthin Concentration of pigment compound diatoxanthin Producer Defined << empty cell >> No Data Producer defined 2.75 31.9 ng (nanograms) pigment per g (gram) dry sediment Zeaxanthin Concentration of pigment compound zeaxanthin Producer Defined << empty cell >> No Data Producer defined 3.03 74.3 ng (nanograms) pigment per g (gram) dry sediment Canthaxanthin Concentration of pigment compound canthaxanthin Producer Defined << empty cell >> No Data Producer defined 21.4 41.6 ng (nanograms) pigment per g (gram) dry sediment Chlorophyll-b Concentration of pigment compound chlorophyll-b Producer Defined << empty cell >> No Data Producer defined 12.7 111.0 ng (nanograms) pigment per g (gram) dry sediment Echinenone Concentration of pigment compound echinenone Producer Defined << empty cell >> No Data Producer defined 4.75 95.4 ng (nanograms) pigment per g (gram) dry sediment Chlorophyll-a Concentration of pigment compound chlorophyll-a Producer Defined << empty cell >> No Data Producer defined 40.7 1060.0 ng (nanograms) pigment per g (gram) dry sediment Pheophytin-a Concentration of pigment compound pheophytin-a Producer Defined << empty cell >> No Data Producer defined 36.3 2760.0 ng (nanograms) pigment per g (gram) dry sediment B-Carotene Concentration of pigment compound b-carotene Producer Defined << empty cell >> No Data Producer defined 6.24 22.9 ng (nanograms) pigment per g (gram) dry sediment GS ScienceBase U.S. Geological Survey mailing address

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