DOI: 10.5061/dryad.z612jm6nf
title: Data from: Biogeochemical patterns in prey species reveal complex mercury exposure pathways from the environment to Aleutian Steller sea lions

description: 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.
description: 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 &lt;10% to meet
 laboratory standards.  
description: # Mercury and isotopes in Aleutian Island (Alaska, USA) fish and
 cephalopods, 2011-2021
 [https://doi.org/10.5061/dryad.z612jm6nf](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: *  FishID                               unique identifier for each fish or cephalopod -  CommonName               common name for the species *  SciName                           scientific name as Genus species; if not identified to species then Family is given -  CollMon                            month of year that fish was collected *  CollYear                            year fish was collected -  SiteDescription               general description of the location where the fish was collected; empty cells show absence of specific site *  Position                            E (east) or W (west) of Amchitka Pass, located in the Aleutian Islands at approximately 180° W longitude -  Mass_gm                         fish mass in grams *  Length_cm                      length in centimeters as fork length (fish) and total length (cephalopods) -  Length_Mantle_cm        for cephalopods only, mantle length in centimeters *  Width_Mantle_cm          for cephalopods only, mantle width in centimeters -  Width_Fin_cm                 for cephalopods only, fin width in centimeters *  d15N_AtAir_Muscle       muscle bulk stable isotope (SI) of nitrogen (δ15N) -  d13C__PDB_Muscle       muscle bulk SI of carbon (δ13C) *  LE_d13C_PDB_Muscle   muscle bulk lipid-extracted (LE) SI of carbon (δ13C),  conducted for fish with CN bulk SI δ13C: δ15N molar ratios &gt; 3.7 -  CNMolarRatio_Muscle       Carbon to nitrogen molar ratio (δ13C: δ15N) calculated as:    (% carbon / % nitrogen)*(14 / 12) *  THg_µg/g_MuscleWW       total mercury concentration (micrograms per gram muscle, equals parts per million) converted to wet weight -  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 &gt; 3.7 were further lipid-extracted; mathematical adjustments were used for other fish with C:N &gt; 3.7.