DOI: 10.5061/dryad.qbzkh18q5
title: Data from: Littoral sediment arsenic concentrations predict arsenic trophic transfer and human health risk in contaminated lakes

description: Lake sediments store metal contaminants from historic pesticide and
 herbicide use and mining operations. Historical regional smelter
 operations in the Puget Sound lowlands have resulted in arsenic
 concentrations exceeding 200 μg As g-1 in urban lake sediments. Prior
 research has elucidated how sediment oxygen demand, warmer sediment
 temperatures, and alternating stratification and convective mixing in
 shallow lakes result in higher concentrations of arsenic in aquatic
 organisms when compared to deeper, seasonally stratified lakes with
 similar levels of arsenic pollution in profundal sediments. In this study
 we examine the trophic pathways for arsenic transfer through the aquatic
 food web of urban lakes in the Puget Sound lowlands, measuring C and N
 isotopes – to determine resource usage and trophic level – and total and
 inorganic arsenic in primary producers and primary and secondary
 consumers. Our results show higher levels of arsenic in periphyton than in
 other primary producers, and higher concentrations in snails than in
 zooplankton or insect macroinvertebrates. In shallow lakes arsenic
 concentrations in littoral sediment are similar to deep profundal
 sediments due to arsenic remobilization, mixing, and redeposition,
 resulting in direct arsenic exposure to littoral benthic organisms such as
 periphyton and snails. The influence of littoral sediment on determining
 arsenic trophic transfer is evidenced by our results which show
 significant correlations between total arsenic in littoral sediment and
 total arsenic in periphyton, phytoplankton, zooplankton, snails, and fish
 across multiple lakes. We also found a consistent relationship between the
 percent inorganic arsenic and trophic level (determined by δ15N) in lakes
 with different depths and mixing regimes. Cumulatively, these results
 combine to provide a strong empirical relationship between littoral
 sediment arsenic levels and inorganic arsenic in edible species that can
 be used to screen lakes for potential human health risk using an easy,
 inexpensive sampling and analysis method.
description: <strong>Study area and site
 characterization</strong> Of the 10 study lakes
 located in the Puget Sound lowland region of Washington State, USA, 8
 lakes are within the predicted deposition field of arsenic-contaminated
 smelter emissions, and two control lakes are located outside the predicted
 deposition field (Pine and Bonney Lakes). Of the 8 lakes potentially
 impacted by aerial fallout of arsenic, littoral sediment concentrations
 range from 7 to 213 µg As g<sup>-1</sup>.
 Previous work reported that Angle Lake and Lake Killarney have
 the greatest concentrations of arsenic in profundal sediment for the 8
 sampled lakes in the predicted deposition field (208 μg
 g<sup>−1</sup> and 206 μg g<sup>−1</sup>,
 respectively. Lake Killarney is shallow (maximum depth 4.6 m) and
 experiences frequent, year-round mixing events (termed ‘polymictic’).
 Angle Lake is deeper (maximum depth 15.8 m) and displays strong seasonal
 stratification. Each type of organism described below was collected from
 Angle Lake and Lake Killarney, and a subset of those organisms was sampled
 from the 8 remaining lakes. A summary of samples collected from each lake
 and the analyses performed is provided in the S1 Table.
 <strong>Sample collection</strong>
 <strong>Water and food web
 sampling</strong> Water samples for dissolved
 arsenic, and phytoplankton and zooplankton tows, were collected from a
 boat at approximately the deepest point in each lake as described
 previously. In June 2019, water samples were collected using a peristaltic
 pump, filtered (0.45 µm Geotech cartridge filter), acidified with 1%
 HNO<sub>3</sub> (v/v) in the laboratory, and allowed to stand
 for 14 days prior to analysis for dissolved arsenic. Duplicate phyto- and
 zooplankton samples were collected in 2016, 2017, and 2019 using a
 vertical net tow (20 μm and 153 μm mesh, respectively) from 1-2 m above
 the lakebed. Phytoplankton were then pre-filtered through a 153 μm sieve
 to remove zooplankton. Plankton were collected on 5.0 µm polycarbonate
 filters and either dried at 60 °C (for total As) or stored at -80 °C (for
 As speciation). Periphyton was grown <em>in
 situ</em> on multiple 23 cm<sup>2</sup> acrylic plates
 assembled into 3 x 3 plate frames and placed at 0.5 m depth in the
 approximate center of each lake. Plates were deployed for at least 35 days
 during the summers of 2019 and 2021. Both sides of each plate were scraped
 of periphyton with a plastic razor blade and rinsed with ultrapure reverse
 osmosis de-ionized water into a filtration vessel. Material was captured
 on 5.0 µm polycarbonate filters and subsamples were either dried at 60 °C
 overnight or stored at -80 °C. Triplicate grab samples of mixed submerged
 macrophytes were harvested from nearshore (1-2 m depth) using an aquatic
 plant rake (Pond & Beach Rake Gen 2) in August and September 2020
 and cleaned of attached sediment. Roots were removed and random portions
 of each rake harvest were either dried at 60 °C overnight or stored at -80
 °C. Insect midge larvae
 (<em>Chironomidae</em>) were collected from sediments in July
 and August 2020 at multiple sites in each lake using a dredge (Wildco
 stainless steel petite ponar). Dredge samples were sifted through a mesh
 sieve to reveal larvae within. Larvae were transferred into a container of
 lake water on ice. In the laboratory, larvae were separated into groups of
 9-10 individuals per composite sample and either dried at 60 °C overnight
 or stored at -80 °C. Chinese mystery snails (<em>Bellamya
 chinensis</em>) were collected in June 2019 and July 2021 from the
 littoral zone (&lt; 2 m depth) of 6 lakes. The collection involved
 hand netting via snorkeling or from a boat. <em>B.
 chinensis</em> were placed on ice in sealed plastic bags on the
 boat, euthanized in the laboratory, and then later thawed and body tissue
 removed from the shell. Pumpkinseed (<em>Lepomis
 gibbosus</em>) and bluegill sunfish (<em>L.
 macrochirus</em>) were collected by beach seining from 5 lakes in
 June 2019 and 2021. A scientific collection permit was approved for fish
 by the Washington Department of Fish and Wildlife (SCP Olden 22-172); no
 permit is required for non-vertebrate sample collection. Field site access
 does not require a permit for publicly accessible lakes in Washington.
 Fish were euthanized and muscle tissue dissected. Fish and snail tissues
 were either dried at 60 °C overnight or stored at -80 °C.
 <strong>Laboratory Analyses</strong>
 Oven-dried samples of periphyton, phyto- and zooplankton,
 macrophytes, <em>Chironomidae</em>, snail whole soft tissue,
 and fish tissue were divided into 2 subsamples for total arsenic and
 δ<sup>13</sup>C and δ<sup>15</sup>N analysis.
 Small portions (&lt; 3 mg) of each food web constituent were
 transferred into tin capsules for stable isotope analysis. All samples
 stored at -80 °C were prepared for arsenic speciation by drying at 85 °C.
 Macrophyte, snail, and fish tissue samples were homogenized using a
 porcelain mortar and pestle, while all other samples were used in entirety
 for arsenic analysis. <strong>Total
 arsenic</strong> Samples for total arsenic
 analysis were prepared by microwave-assisted (CEM MARS 5) total digestion
 protocol (modified EPA method 3015a) using trace metal grade
 HNO<sub>3</sub> in pressurized digestion vessels. After
 digestion, sample solutions were diluted to 2% (v/v)
 HNO<sub>3</sub>. Concentrations of total arsenic in water and
 digested sediment, periphyton, plankton,
 <em>Chironomidae</em>, and <em>B. chinensis</em>
 and fish tissue samples were determined by inductively-coupled plasma mass
 spectrometry (ICP-MS; Agilent 7900). Calibration was performed using a
 certified multi-element standard (Agilent Multi-element calibration
 standard-2A). Efficacy of the digestion procedure was verified using
 certified reference material BCR-414 (Trace elements in plankton), NIST
 2711a (Montana Soil II), and DOLT-5 (dogfish liver) which yielded a
 recovery of 90 ± 15% (n = 8), 92 ± 16% (n = 10) and 91 ± 12% (n = 22),
 respectively. Analytical accuracy of the ICP-MS method was assessed using
 certified reference material NIST 1640a (trace elements in natural water),
 which had a recovery of 87 ± 6% (n = 14) for arsenic. The limit of
 detection (LOD) for arsenic was 0.25 μg L<sup>-1</sup>.
 Samples below the limit of detection were assigned a value of 0.125 μg
 L<sup>-1 </sup>(half the LOD).
 <strong>Arsenic speciation</strong>
 Arsenic speciation of phyto- and zooplankton collected in 2016
 and 2017 was determined in the Trace Element Analysis laboratory at
 Dartmouth College using methods based on Taylor and Jackson [42]. Plankton
 samples were freeze-dried and transferred from polycarbonate filters into
 sample vials and 10% methanol was added. Samples were sonicated in a 30 °C
 bath for 2 h, then filtered (0.2 µm) to remove residual solids. The
 supernatant was eluted with 20 mM
 (NH<sub>4</sub>)<sub>2</sub>CO<sub>3</sub> (1.1 mL min<sup>−1</sup>) on an Agilent LC1120 liquid chromatograph. Arsenic species were separated using an anion-exchange column (Hamilton PRP-X100) at 35 °C and then analyzed on an Agilent 8900 triple quadrupole ICP-MS. Analytical accuracy was verified using a secondary standard with a recovery of 104 ± 2% (n = 3). The extraction efficiency (sum of species/total As by ICP-MS) for phytoplankton was 10 ± 6% (n = 4) and 23 ± 2 % (n = 2) for zooplankton. The speciation of arsenic in phyto- and zooplankton collected in 2019, periphyton, macrophytes, <em>Chironomidae</em>, <em>B. chinensis</em>, and fish tissue were also determined at the Trace Element Analysis laboratory at Dartmouth College, following a dilute acid heat assisted extraction (modified from [43]). An aliquot of the extract was diluted 1:1 with 200 mM NH<sub>4</sub>CO<sub>3</sub> and analyzed for arsenic species by ion chromatography coupled to inductively coupled plasma mass spectrometry (IC-ICP-MS). A Dionex AS14 anion-exchange column was used with an NH<sub>4</sub>CO<sub>3</sub> gradient to separate arsenate, arsenite, dimethylarsinic acid, monomethylarsonic acid, and arsenosugars (run time of 7 minutes, flow rate of 1 mL min<sup>-1</sup>, and injection volume of 20 μL). The system was calibrated using primary standard solutions of the arsenic species (Sigma Aldrich, Spex certiprep) and NIST 2669a urine level II was used for quality control. The extraction efficiency was 80 ± 16% (n = 6) for fish, 57 ± 27% (n = 6) for <em>B. chinensis</em>, 88 ± 9% (n = 2) for <em>Chironomidae</em>, 55 ± 14% (n = 2) for macrophytes, 124 ± 45% (n = 2) for zooplankton, 87 ± 0.9% for phytoplankton (n = 2), and 60 ± 17% (n = 2) for periphyton. Other studies report similar ranges for extraction efficiencies across different environmental materials using equivalent methods. <strong>Stable isotope analysis</strong> To explore how differences in lake morphometry may influence arsenic trophic transfer, we conducted a food-web investigation in lakes Angle and Killarney, two spatially proximate lakes with similar levels of arsenic in profundal surface sediments but differing maximum depths and mixing regimes. We used <sup>13</sup>C/<sup>12</sup>C as a proxy for basal C resources and <sup>15</sup>N/<sup>14</sup>N as a proxy for trophic position, which together indicate resource use. Periphyton, plankton, macrophyte, <em>Chironomidae</em>, <em>B. chinensis</em>, and fish tissue samples were dried for 24–48 h at 60 °C, homogenized with mortar and pestle, and encapsulated in tin capsules. Tissues were sent to the University of California Davis Stable Isotope Facility and analyzed for ratios of stable isotopes (<sup>13</sup>C/<sup>12</sup>C and <sup>15</sup>N/<sup>14</sup>N) using an elemental analyzer (PDZ Europa ANCA-GSL) interfaced with an isotope ratio mass spectrometer (PDZ Europa 20-20; Sercon Ltd., Cheshire, UK). Data are reported as permil (‰) relative differences from standards of Vienna Pee Dee Belemnite for C and atmospheric N, expressed as delta (δ) units. Long-term standard deviations for estimates of natural abundance stable isotope values based on reference material at the University of California-Davis are 0.2‰ for δ<sup>13</sup>C and 0.3‰ for δ<sup>15</sup>N.
description: # Data from: Littoral sediment arsenic concentrations predict arsenic
 trophic transfer and human health risk in contaminated lakes
 [https://doi.org/10.5061/dryad.qbzkh18q5](https://doi.org/10.5061/dryad.qbzkh18q5) This dataset includes measurements from multiple shallow lakes in Puget Sound lowlands of western Washington, USA, of inorganic and total arsenic in water, sediments, and organisms from multiple trophic levels (phytoplankton, zooplankton, periphyton, snails, and sunfish), coupled with carbon and nitrogen stable isotope measurements. ## Description of the data and file structure Data are provided in .XLSX format, organized by study lake and medium or organism. This file has three tabs, and the data for each is described below. #### Total As & As speciation in org "N/A" = not analyzed; only samples indicated were analyzed for total arsenic, arsenic speciation, or stable isotope analysis * *lake* - lake where each organism was collected (Hull et al. 2023; Figure 1) * *species* - organism type/species collected * *sample type* - brief description of how each organism was collected; for additional details see methods above * *collection date* - date of organism collection * *total As µg/g* - total arsenic concentration as determined by acid digestion and analysis by ICP-MS * *% inorganic As* - ratio of the sum of *As(V) µg/g *and *As(III) µg/g* normalized to *total As µg/g* * *As(V) µg/g* - concentration of arsenate (+5 oxidation state) * *As(III) µg/g* - concentration of arsenite (+3 oxidation state) * *DMA µg/g* - concentration of dimethylarsinic acid * *MMA µg/g* - concentration of monomethylarsonous acid * *combined Arseno-sugars µg/g* - concentration of the sum of all arseno-sugars (i.e., arsenobetaine, arsenocholine, and other unspecified compounds) * *δ13CVPDB (‰)* - stable isotope ratio of 13C to 12C using Vienna PeeDee Belemnite as a reference * *δ15NAir (‰)* - stable isotope ratio of 15N to 14N using N2 in air as a reference #### Total As in littoral sediment "N/A" = not available; Date Collected information was unavailable for two samples from Steel Lake * *Lake* - lake where each organism was collected (Hull et al. 2023; Figure 1) * *Date Collected* - date of sediment collection * *total As µg/g* - total arsenic concentration as determined by acid digestion and analysis by ICP-MS #### Total As in water column * *Lake* - lake where each organism was collected (Hull et al. 2023; Figure 1) * *date* - date of sample collection * *Depth (m)* - depth of water sampled in lake * *Temperature (C)* - temperature of water in degrees Celcius at depth and time of sample collection * *DO (mg/L)* - dissolved oxygen (O2) concentration of water at depth and time of sample collection * *dissolved As (µg/L)* - dissolved arsenic concentration as determined by filtration through 0.4 µm filter and analysis by ICP-MS