Data from: Biogeochemical patterns in prey species reveal complex mercury exposure pathways from the environment to Aleutian Steller sea lions
Data files
Mar 06, 2025 version files 202.20 KB
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qry_FishDryadExport_UPLOADED_FILE_revised.csv
199.29 KB
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README.md
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Abstract
Several wildlife species exhibit marked spatial variation in toxicologically relevant tissue concentrations of mercury across the Aleutian Islands of Alaska, most notably the endangered Steller sea lion (Eumetopias jubatus). To unravel potential environmental and trophic pathways driving mercury variation in this species of concern, we investigated spatiotemporal and ecological patterns in total mercury concentrations and stable isotope ratios of carbon and nitrogen from muscle tissues of twelve mid-trophic level prey species of the region (n = 1461). Dividing samples into island groups explained biogeochemical variation better than larger spatial resolutions, with Amchitka Pass and Buldir Pass acting as strong geographic break points. Species-specific relationships between muscle biogeochemistry and length were common, and benthic feeding and increased trophic position were associated with higher total mercury concentrations. Considered together, tissue biogeochemical markers in this region are dependent on location and the species upon which they forage in remarkably nuanced manners.
https://doi.org/10.5061/dryad.z612jm6nf
Description of the data and file structure
The data consist of the mean mercury concentration (µg/g) of technical replicates and bulk stable isotope ratios (carbon, nitrogen) of homogenized muscle (fish) or mantle (cephalopod) collected from 1628 individuals, captured adjacent to the Aleutian Islands, Alaska during 2011, 2013, 2014, 2015, 2020 and 2021.
Files and variables
The data are organized into 18 columns:
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FishID unique identifier for each fish or cephalopod
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CommonName common name for the species
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SciName scientific name as Genus species; if not identified to species then Family is given
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CollMon month of year that fish was collected
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CollYear year fish was collected
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SiteDescription general description of the location where the fish was collected; empty cells show absence of specific site
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Position E (east) or W (west) of Amchitka Pass, located in the Aleutian Islands at approximately 180° W longitude
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Mass_gm fish mass in grams
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Length_cm length in centimeters as fork length (fish) and total length (cephalopods)
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Length_Mantle_cm for cephalopods only, mantle length in centimeters
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Width_Mantle_cm for cephalopods only, mantle width in centimeters
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Width_Fin_cm for cephalopods only, fin width in centimeters
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d15N_AtAir_Muscle muscle bulk stable isotope (SI) of nitrogen (δ15N)
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d13C__PDB_Muscle muscle bulk SI of carbon (δ13C)
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LE_d13C_PDB_Muscle muscle bulk lipid-extracted (LE) SI of carbon (δ13C), conducted for fish with CN bulk SI δ13C: δ15N molar ratios > 3.7
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CNMolarRatio_Muscle Carbon to nitrogen molar ratio (δ13C: δ15N) calculated as: (% carbon / % nitrogen)*(14 / 12)
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THg_µg/g_MuscleWW total mercury concentration (micrograms per gram muscle, equals parts per million) converted to wet weight
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THg_µg/g_MuscleDW total mercury concentration (micrograms per gram muscle, equals parts per million) in dry weight
Missing Data
Missing data are indicated as “NA”. Examples of missing data include:
- no mantle length/width or fin width for non-cephalopods
- no LE (lipid extracted) d13C data for many fish; only a subset of fish with C:N molar ratio > 3.7 were further lipid-extracted; mathematical adjustments were used for other fish with C:N > 3.7.
- Fish were collected during commercial fishing operations by Ocean Peace, Inc. A subset of bycaught species were stored frozen on the ship until transferred to the University of Alaska Fairbanks (UAF).
- At UAF, fish were identified to species, photographed, weighed, and measured. Muscle samples were collected from the left lateral aspect of the fish, centrally located along the length of the fish.
- Muscle samples were freeze-dried and homogenized into a flour.
- Total mercury concentrations were obtained using a Direct Mercury Analyzer (Milestone DMA-80). Standard reference materials had 100% ±10% recoveries from theoretical concentrations during each day of testing.
- Data were reported as the mean (µg/g) of the technical replicates. The percent coefficient of variation (%CV) was calculated for each set of technical replicates; desired %CV was <10% to meet laboratory standards.