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. 2021 Jan 30;35(2):e8992.
doi: 10.1002/rcm.8992.

Validation of dried blood spot sampling for determining trophic positions of Arctic char using nitrogen stable isotope analyses of amino acids

Benjamin D Barst  1 , Derek C G Muir  2 , Diane M O'Brien  3   4 , Matthew J Wooller  1   5   6
Affiliations

Validation of dried blood spot sampling for determining trophic positions of Arctic char using nitrogen stable isotope analyses of amino acids

Benjamin D Barst et al. Rapid Commun Mass Spectrom. .

Abstract

Rationale: Dried blood spots (DBSs) are gaining popularity for biomarker analyses in ecological research due to their advantages for use in field-based research and in remote settings; however, many DBS biomarkers remain unvalidated. We validated the application of compound-specific stable nitrogen isotope analyses of amino acids (CSIA-AAs) to field-prepared DBSs for determining trophic positions of wild-caught Arctic char (Salvelinus alpinus).

Methods: Whole blood and muscle from Arctic char were collected, and DBSs were created in the field. We measured the stable nitrogen isotope ratios (expressed as δ15 N values) of the amino acids glutamic acid (Glu) and phenylalanine (Phe) isolated from Arctic char samples using CSIA-AAs. We then compared amino acid δ15 N values from DBSs and the other sample types (whole blood and muscle) from the same specimens. We calculated and compared trophic position estimates generated from whole blood, DBSs, and muscle.

Results: The δ15 N values of Glu and Phe, as well as trophic position estimates from DBSs, were highly correlated with δ15 N values and estimates from both whole blood and muscle. The DBS amino acid δ15 N values and trophic position estimates agreed well with those from whole blood. Although mean differences between amino acid δ15 N values from DBSs and muscle were noted, the offsets were small and resulted in a 0.2 mean difference between trophic position estimates for DBSs and muscle.

Conclusions: We demonstrate that the application of CSIA-AAs to field-prepared DBSs of Arctic char generates similar trophic position estimates to those from whole blood and muscle. We suggest that DBSs could be developed as a minimally invasive sampling technique to study feeding ecology of wild fish and perhaps other organisms of interest.

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Figures

Figure 1.
Figure 1.
Comparisons of glutamic acid δ15N (δ15NGlu; Panels A and B) and phenylalanine δ15N (δ15NPhe; Panels C and D) values from dried blood spots (DBSs) and whole blood (WB) of landlocked Arctic char (Salvelinus alpinus). Panels A and C present linear regressions where the gray shaded regions indicate the 95 % confidence regions about the fitted lines. Panels B and D present Bland-Altman plots showing relationships between the average of the δ15N values for the two sample types and the difference between δ15N values for the two sample types. The blue solid line represents the bias or mean difference between the two measurements, the dashed blue lines represents the 95 % confidence interval for the bias, and the red dashed lines represent the 95 % confidence interval for all of the measurements. In all panels, the different symbols represent Arctic char from different lakes.
Figure 2.
Figure 2.
Comparisons of glutamic acid δ15N (δ15NGlu; Panels A and B) and phenylalanine δ15N (δ15NPhe; Panels C and D) values from dried blood spots (DBSs) and muscle of landlocked Arctic char (Salvelinus alpinus). Panels A and C present linear regressions where the gray shaded regions indicate the 95 % confidence regions about the fitted lines. Panels B and D present Bland-Altman plots showing relationships between the average of the amino acid δ15N values for the two sample types and the difference between amino acid δ15N values for the two sample types. The blue solid line represents the bias or mean difference between the two measurements, the dashed blue lines represents the 95 % confidence interval for the bias, and the red dashed lines represent the 95 % confidence interval for all of the measurements. In all panels, the different symbols represent Arctic char from different lakes.
Figure 3.
Figure 3.
Comparisons of dried blood spot (DBS) trophic position estimates (TP) with estimates from whole blood (WB; Panels A and B) and muscle (Panels C and D) of landlocked Arctic char (Salvelinus alpinus). Panels A and C present linear regressions where the gray shaded regions indicate the 95 % confidence regions about the fitted lines. Panels B and D present Bland-Altman plots showing relationships between the average of the estimates for the two sample types and the difference between the estimates for the two sample types. The blue solid line represents the bias or mean difference between the two estimates, the dashed blue lines represents the 95 % confidence interval for the bias, and the red dashed lines represent the 95 % confidence interval for all of the estimates. In all panels, the different symbols represent Arctic char from different lakes.
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