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Effects of acid treatment on carbon and nitrogen stable isotope ratios in ecological samples: a review and synthesis
Author(s) -
Schlacher Thomas A.,
Connolly Rod M.
Publication year - 2014
Publication title -
methods in ecology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.425
H-Index - 105
ISSN - 2041-210X
DOI - 10.1111/2041-210x.12183
Subject(s) - stable isotope ratio , isotopes of nitrogen , nitrogen , isotopes of carbon , chemistry , isotope , isotope analysis , organic matter , carbonate , dissolution , carbon fibers , environmental chemistry , δ13c , δ15n , total organic carbon , ecology , biology , organic chemistry , materials science , composite material , physics , quantum mechanics , composite number
Summary Stable isotopes of carbon and nitrogen are mainstay tracers in diverse fields of ecology, particularly in studies of food webs. Investigators are generally interested in tracing dietary C and N, and hence routinely remove non‐dietary, inorganic C contained in calcified structures (e.g. shells, bones) by chemical dissolution of the carbonates. Acid treatment can, however, isotopically fractionate samples if part of the organic matter is lost or chemically modified, resulting in potentially altered δ 13 C and δ 15 N values. Here, we synthesize the effects of acid treatments on stable isotope analysis reported in the literature, showing that: (i) the method can change both δ 13 C and δ 15 N values; (ii) shifts in δ 13 C are generally, but not always, consistent with expectations of more depleted carbon ratios after the removal of the isotopically heavier inorganic carbonates; (iii) nitrogen ratios either decrease or increase in 15 N content; and (iv) the majority (74–79% of comparisons) of reported changes to δ 13 C and δ 15 N values attributable to acid treatment are <1 ‰, but larger acid effects can occur. Acidification is needed if mechanical removal of calcified structures is unfeasible in carbonate‐rich sample matrices containing low organic C and N, but should otherwise be very carefully considered before its use as a routine pre‐treatment step of biological samples in isotope ratio mass spectrometry.