Effects of blood anticoagulants on stable isotope values of sea turtle blood tissue

Abstract

Collecting tissue samples from sea turtles for stable isotope analysis often occurs at remote field sites. For blood tissue, samples are treated with an anticoagulant that allows for later separation of plasma from cellular components. However, the effect of this technique on stable isotope values of sea turtle blood has not been established. We measured the effects of 3 widely used anticoagulants, acid citrate dextrose (ACD), sodium heparin (SH) and ethylenediaminetetraacetic acid (EDTA), on stable carbon (δ 13C) and stable nitrogen (δ 15N) values in whole blood, red blood cells, and blood plasma of 11 green turtles Chelonia mydas captured in San Diego Bay, California, USA. Vials containing each of the 3 blood preservatives as well as a vial containing no additive (i.e. control vial) were filled in random order. Blood in the no-additive vial was immediately separated into fractions (e.g. red blood cells, plasma) via centrifugation, whereas blood collected in the treatment vials was chilled and then centrifuged 48 h after collection. We found that, relative to the controls, ACD-preserved whole blood and blood plasma were 13C enriched, EDTA-treated red blood cells and plasma were 15N de pleted, and SH-treated whole blood was 15N en riched. Because SH was the only anticoagulant with no measured effect on blood plasma and red blood cells-the most commonly studied blood fractions for sea turtle stable isotope studies-we recommend its exclusive use as a blood anticoagulant for field studies where prompt centri -fugation is not possible.