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Document Type

Research

Keywords

Rana sphenocephala, Hyla chrysoscelis, methyl mercury, chlorpyrifos, atrazine, UV radiation, metamorphosis, amphibians, malformations

Abstract

Multiple stressors have been proposed as causative agents for declining populations and increased incidence of malformations in amphibians although few studies have examined possible interactions among these stressors. We measured interactive effects of UV radiation, three chemicals, and interspecific competition (with Rana 1phenocephala) on multiple endpoints in Hyla chrysoscelis using a center point- and chemical-free control-enhanced 24 factorial design. UV radiation was transmitted or filtered using OP-4 or OP-3 acrylite filters installed above 72, 500-liter mesocosms on 16 May 1997. Methyl mercury, chlorpyrifos, and atrazine were applied at levels of 0, 10, 50, and 100 % of 400 ppb, 30 ppb, and 192 ppb, respectively, on 8 June. Hatching success and larval mortality were assessed 1, 2, 4, 8, 16, and 32 days after chemical application. After sampling on day 32, chemicals were reapplied to 24 mesocosms, initial water levels were restored in 24 additional mesocosms, and the remaining mesocosms were unmanipulated. On day 33, we placed 25 Hyla eggs in each mesocosm to perform a complete larval assessment of interacting stressors on growth, development, metamorphosis, and incidence of malformations. Interactions among stressors affected hatching success, developmental time, number of metamorphs, and incidence of malformation. Single effects of stressors were uncommon in that only larval mortality was unaffected by potential stressor interactions. If interactive effects of stressors are not evaluated in experiments examining population declines and malformations, results may be misinterpreted leading to ineffective conservation efforts.

Publication Date

September-December 2000

Journal Title

Journal of the Iowa Academy of Science

Volume

107

Issue

3-4

First Page

61

Last Page

66

Copyright

© Copyright 2000 by the Iowa Academy of Science, Inc.

Language

EN

File Format

application/pdf