LIMITS ON BENTHIC FORAMINIFERAL CHEMICAL-ANALYSES AS PRECISE MEASURESOF ENVIRONMENTAL PROPERTIES

The ''practical precision'' of benthic foraminiferal Cd/Ca analysis (d efined as the reproducibility on replicate picks of foraminifera from the same sample) is poorer than the analytical precision (defined as t he reproducibility of replicate solutions analyzed during a 6-year per iod). Conversely, the reproducibility on splits of homogenized fragmen ts (obtained by gently crushing foraminifera into approximately 50 fra gments each and mixing the fragments) is close to the analytical preci sion. This experiment rules out variability in sample-to-sample handli ng as a cause of imprecision, and it strongly implicates individual-to -individual specimen variability as the major factor limiting reproduc ibility in foraminiferal Cd/Ca analysis. This inference is confirmed b y a pilot study using a new method for the analysis of single specimen s of benthic foraminifera: individual benthic foraminifera from a samp le 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 proced ures, but rather the number of individuals available for analysis.