Effects of exposure to a combination of zinc- and lead-spiked sediments on mouthpart development and growth in Chironomus tentans.

ABSTRACT

Exposures to either zinc or lead in contaminated sediments have been shown to induce characteristic deformities in larval chironomids. This study examined the effects of exposure to lead and zinc in combination on Chironomus tentans larvae. Proportions of mouthpart deformities in populations of larvae reared in sediments containing nominal combinations of lead and zinc were tested for additive, synergistic, and antagonistic interactions using logistic regression. Metal body burdens, body size measurements, and survival were used to evaluate toxicity and developmental impacts. Results demonstrate zinc and lead mixtures produce fewer deformities than the individual metal, so their interaction may be characterized as antagonistic. However, exposure to the metal mixtures also caused delayed development and failure to hatch. The apparent decline in deformities may be an artifact of higher mortalities or developmental effects. This research provides better understanding of some of the problems and considerations for use of chironomid population deformity proportions in bioassessments for sediment metal contamination.