Limits on benthic foraminiferal chemical analyses as precise measures of environmental properties

The “practical precision ” of benthic foraminiferal Cd/Ca analysis (defined as the reproducibility on repli-cate picks of foraminifera from the same sample) is poorer than the analytical precision (defined as the re-producibility of replicate solutions analyzed during a 6-year period). Conversely, the reproducibility on splits of homogenized fragments (obtained by gently crushing foraminifera into-50 fragments each and mixing the fragments) is close to the analytical precision. This ex-periment rules out variability in sample-to-sample han-dling as a cause of imprecision, and it strongly implicates individual-to-individual specimen variability as the ma-jor factor limiting reproducibility in foraminiferal Cd/ Ca analysis. This inference is confirmed by a pilot study using a new method for the analysis of single specimens of benthic foraminifera: individual benthic foraminifera from a sample show large variability from one individual to the next. Hence, the fundamental factor limiting the effective precision of foraminifera Cd/Ca analysis is not analytical precision or laboratory sampling procedures, but rather the number of individuals available for anal-ysis