Zooplankton filtering rates: Error due to loss of radioisotopic label in chemically preserved samples

Abstract

Zooplankton fed 32P‐labeled yeast or 14C‐labeled algae were preserved with Formalin, ethanol, or Lugol’s iodine and the subsequent loss of labeled materials was followed by analysis of sample filtrates. The commonly used combination of 32P‐labeled yeast and Formalin preservation produced maximal loss in both magnitude and duration, reaching a value of 73% loss after 3 days; ethanol preservation resulted in only 5% loss for the same food. Lugol’s iodine yielded the best results for animals fed 14C‐labeled algae, resulting in a 40% loss that stabilized within 3 h. Nonchemical preservation (heat‐killing and drying) produced filtering rates comparable with those of the best chemical preservative.