GUT CONTENT WEIGHT AND CLEARANCE RATE FOR 3 SPECIES OF FRESH-WATER INVERTEBRATES

There is concern for potential error in the accurate estimation of che mical bioaccumulation in benthic organisms due to chemicals associated with gut contents (sediments). In this study the benthic macroinverte brates Hexngenia limbata, Chironomus tentans, and Lumbriculus variegat us were exposed to five sediments from the Lower Fox River/Green Bay a rea of Wisconsin to determine the percentage of their weight due to gu t contents and the rare at which guts were emptied when the animals we re held in clean water. Upon removal from the test sediments, inorgani c gut contents in H. limbata, C. tentans, and L. variegatus represente d approximately 9, 10, and 10% of their whole body dry weights, respec tively. Depuration rates were relatively rapid, with mayflies, midges, and oligochaetes losing approximately 75, 90, and 100% of their gut c ontents during the first 12 h of depuration. This suggests that a 12-2 4-h holding period in clean water at the conclusion of sediment bioacc umulation tests with the three species should be sufficient to elimina te potential bias in tissue residue concentrations due to gut contents .