The effect of acidification and the combined effects of acidification/lipid extraction on carbon stable isotope ratios for sub-arctic and arctic marine zooplankton species

• Published in: Polar biology Vol. 37; no. 10; pp. 1541 - 1548
• Main Authors: Pomerleau, Corinne, Winkler, Gesche, Sastri, Akash, Nelson, R. John, Williams, William J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.10.2014; Springer; Springer Nature B.V
• Subjects: Analysis; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Carbonates; Ecology; Fundamental and applied biological sciences. Psychology; Isotopes; Life Sciences; Lipids; Marine biology; Microbiology; Oceanography; Particular ecosystems; Plankton; Plant Sciences; Sea water ecosystems; Short Note; Synecology; Zoology; Arctic Region; Lipid extraction; Stable isotopes; Acidification; Carbonates; Arctic; Carbon; Zooplankton; Lipids; Subpolar zone; Marine environment; Polar region; Ratio; Isotopes
• ISSN: 0722-4060; 1432-2056
• DOI: 10.1007/s00300-014-1540-8

Stable isotope ratios of carbon ( δ 13 C) in zooplankton are widely applied in ecosystem-level studies of energy flux and trophic interactions. Carbonate (CaCO 3 ) and lipid content are highly variable both among and within zooplankton species. Such variability can arise from the δ 13 C-depleted nature of lipids as well as differences in carbon incorporation among tissues (e.g., relative amount of carbonate). Critically, the impact of the common lipid- and carbonate-normalization steps of extraction and acidification is poorly understood and applied in an inconsistent manner. Here, we investigated the effect of lipid extraction and sample acidification (CaCO 3 removal) on δ 13 C in sub-arctic and arctic marine zooplankton species. Our results indicate that, with the exception of the shelled mollusc Limacina helicina , acidification of samples can be omitted for all other marine zooplankton considered in this study. In the case of L. helicina , δ 13 C can be corrected for carbonate content using the linear equation developed in this study. In contrast, the δ 13 C for all species was significantly enriched by a combination of lipid extraction and acidification (up to +4.9 ‰) prior to stable isotope analysis. Our data were used to develop simple, predictive species-specific correction models for lipid-acid-normalized δ 13 C using C:N and/or untreated δ 13 C values. Our results indicate that the δ 13 C value for all species, including those with lower C:N ratios (~3–4), should be corrected for lipid content. We recommend lipid extraction whenever possible, or else the use of species/taxon-specific δ 13 C lipid-normalization models for accurate determination of carbon sources and dynamics for arctic and sub-arctic marine zooplankton.