Live controls for radioisotope tracer food chain experiments using meiofauna

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Abstract
Formalin poisoned samples are inadequate for measuring the amount of label to be subtracted as control values for certain food chain studies that employ radioactive tracers. In some studies, tracer is added just before incubation to label food during the feeding study. Commonly, parallel, poisoned incubations are used to distinguish between biotic and abiotic label incorporation. But, a poisoned control does not account for label that could enter a consumer via active transport, epicuticular microfloral uptake or grazing on labeled, non-food particles. Experiments were performed to test if label uptake is greater in live non-grazing than dead organisms. Marine benthic meiofauna incorporate from 3-133 times more tracer when they are alive and not grazing than when they are formalin killed. Control experiments with live animals should be performed to measure all processes by which label can enter consumers in food chain experiments.
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