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Dried Blood Spot Sampling of Landlocked Arctic Char (Salvelinus alpinus) for Estimating Mercury Exposure and Stable Carbon Isotope Fingerprinting of Essential Amino Acids.

ABSTRACT: Dried blood spots (DBS), created by applying and drying a whole blood sample onto filter paper, provide a simple and minimally invasive procedure for collecting, transporting, and storing blood. Because DBS are ideal for use in field and resource-limited settings, we aimed to develop a simple and accurate DBS-based approach for assessing mercury (Hg) exposure and dietary carbon sources for landlocked Arctic char, a sentinel fish species in the Arctic. We collected liquid whole blood (from the caudal vein), muscle, liver, and brains of Arctic char (n = 36) from 8 lakes spanning a Hg gradient in the Canadian High Arctic. We measured total Hg concentrations ([THg]) of field-prepared DBS and Arctic char tissues. Across a considerable range, [THg] of DBS (0.04-3.38 μg/g wet wt) were highly correlated with [THg] of all tissues (r² range = 0.928-0.996). We also analyzed the compound-specific carbon isotope ratios (expressed as δ¹³ C values) of essential amino acids (EAAs) isolated from DBS, liquid whole blood, and muscle. The δ¹³ C values of 5 EAAs (δ¹³ C_EAAs ; isoleucine [Ile], leucine [Leu], phenylalanine [Phe], valine [Val], and threonine [Thr]) from DBS were highly correlated with δ¹³ C_EAAs of liquid whole blood (r² range = 0.693-0.895) and muscle (r² range = 0.642-0.881). The patterns of δ¹³ C_EAAs of landlocked Arctic char were remarkably consistent across sample types and indicate that EAAs are most likely of algal origin. Because a small volume of blood (~50 µL) dried on filter paper can be used to determine Hg exposure levels of various tissues and to fingerprint carbon sources, DBS sampling may decrease the burdens of research and may be developed as a nonlethal sampling technique. Environ Toxicol Chem 2020;39:893-903. © 2020 SETAC.

SUBMITTER: Barst BD

PROVIDER: S-EPMC7748106 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Polymorphism facilitates coexistence of divergent morphs (e.g., phenotypes) of the same species by minimizing intraspecific competition, especially when resources are limiting. Arctic char (Salvelinus sp.) are a Holarctic fish often forming morphologically, and sometimes genetically, divergent morphs. In this study, we assessed the morphological and genetic diversity and divergence of 263 individuals from seven populations of arctic char with varying length-frequency distributions across two distinct groups of lakes in northern Alaska. Despite close geographic proximity, each lake group occurs on landscapes with different glacial ages and surface water connectivity, and thus was likely colonized by fishes at different times. Across lakes, a continuum of physical (e.g., lake area, maximum depth) and biological characteristics (e.g., primary productivity, fish density) exists, likely contributing to characteristics of present-day char populations. Although some lakes exhibit bimodal size distributions, using model-based clustering of morphometric traits corrected for allometry, we did not detect morphological differences within and across char populations. Genomic analyses using 15,934 SNPs obtained from genotyping by sequencing demonstrated differences among lake groups related to historical biogeography, but within lake groups and within individual lakes, genetic differentiation was not related to total body length. We used PERMANOVA to identify environmental and biological factors related to observed char size structure. Significant predictors included water transparency (i.e., a primary productivity proxy), char density (fish·ha-1), and lake group. Larger char occurred in lakes with greater primary production and lower char densities, suggesting less intraspecific competition and resource limitation. Thus, char populations in more productive and connected lakes may prove more stable to environmental changes, relative to food-limited and closed lakes, if lake productivity increases concomitantly. Our findings provide some of the first descriptions of genomic characteristics of char populations in arctic Alaska, and offer important consideration for the persistence of these populations for subsistence and conservation.

Project description:Arctic char (Salvelinus alpinus) is a facultatively anadromous fish species that is critically important to many Inuit communities in the Canadian Arctic. Plasticity in life history has allowed the species to persist in a diversity of challenging Holarctic environments. Despite their ecological and cultural importance and their presence in aquatic ecosystems that are ice-covered for much of the year, few under-ice studies of Arctic char have been conducted. Most winter studies of adult Arctic char have focused on lakes, where they typically overwinter. Several populations of Arctic char, however, overwinter in large river systems, and subsistence fishers have reported that Arctic char overwinter in the lower reaches of the Coppermine River. The Coppermine River is a large Arctic river that flows into Coronation Gulf near Kugluktuk, Nunavut, Canada. The authors used acoustic telemetry to investigate the overwintering ecology of Arctic char in the region. Consistent with local knowledge, they detected Arctic char overwintering within the fluvial environment of the Coppermine River from 2018 to 2020. Unlike other fluvial environments known to be used by overwintering Arctic char, the lower reaches of the Coppermine River are completely ice-covered throughout the winter, are of moderate depths (3.8-14.1 m) and have no known groundwater inputs. Acoustic telemetry observations indicated long-distance movement (7-8 km) within the river in early winter (October) in response to dynamic ice formation. Under-ice movement generally declined 2 weeks after river freeze-up but continued throughout winter in the lower 5 km of the river, where there were fewer under-ice disturbances. Migration into the marine environment before river ice break-up (June), as well as winter (November-May) movements into and within the marine environment, was unexpectedly observed for some fish. Under-ice use of the marine environment is unusual for Arctic char at the distances observed (up to 18 km) and has not previously been documented at the temperatures (fish body temperatures from -0.76 to 1.90°C) observed. Results allow further understanding of the diverse life-history tactics employed by Arctic char and lay a foundation for future research into fluvial and other diverse overwintering tactics employed by the species.

Dataset Information

Dried Blood Spot Sampling of Landlocked Arctic Char (Salvelinus alpinus) for Estimating Mercury Exposure and Stable Carbon Isotope Fingerprinting of Essential Amino Acids.

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