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Exploring the effects of temperature and resource limitation on mercury bioaccumulation, growth and energetics, and behavior in Fundulus heteroclitus.
Citation:
Clark, B., K. Buckman, D. Miller, A. Bertrand, I. Kirby, D. Champlin, C. Chen, AND D. Nacci. Exploring the effects of temperature and resource limitation on mercury bioaccumulation, growth and energetics, and behavior in Fundulus heteroclitus. Society of Toxicology (SOT) 57th Annual Meeting and ToxExpo, San Antonio, Texas, March 11 - 15, 2018.
Impact/Purpose:
This project addresses two questions. First, there is a need for better data to connect laboratory-based experiments to models of wild population outcomes to build robust adverse outcome pathways of the ecological effects of stressors. Second, there is a need to understand how temperature and food availability affect how much mercury fish accumulate from their diet. To address these questions we fed a common estuarine fish, the mummichog (Fundulus heteroclitus), varied levels of tuna contaminated with mercury at high and low temperatures and measured the effects on growth and the accumulation of mercury from food. In a second experiment, a diet containing mercury was fed to adult mummichogs for five months, and we measured changes in the behavior of their young offspring. These data will contribute to models of how food availability and temperature interact to affect the available energy a fish has for growth, and how that interaction affects accumulation of mercury in fish tissue.
Description:
Aquatic ecosystems are affected by changes in both temperature and resource availability. While higher temperatures may result in increased food consumption and increased mercury (Hg) accumulation, they may also increase growth and reduce Hg tissue concentration through somatic dilution. Dynamic energy budget theory provides a broad and generalizable framework based on first principles of energy metabolism that is well suited to understand these interactions, allowing joint acquisition and interpretation of chemical exposure and stressor effect information to be translated into demographic rate changes. In the current study, we conducted growth and bioaccumulation experiments to examine the interaction of temperature and resource availability on Hg accumulation and effects in the estuarine fish Fundulus heteroclitus (mummichog). Juvenile mummichog were fed 3.3% or 10% of their dry body weight/day with tuna naturally contaminated with Hg and held at either 15 or 27 °C for 28 days. Growth was low in most treatments, except in fish fed 10% body weight held at 27 °C (40% weight and 12% length increase). Methylmercury (MeHg) accumulation was similar across feeding conditions but increased with temperature (~17-fold increase in MeHg concentration at 27 °C and ~7-fold increase at 15 °C, regardless of feeding rate). In subsequent experiments, mummichogs from were fed either a high or low MeHg diet to assess the effect on behavior in offspring. Fish were strip-spawned every two weeks during the feeding period. Adults were sampled for total Hg concentration at the start and end of the experiment, and egg MeHg concentration was measured in a subset eggs from each spawning event. Danioscope software was used to assess the heart rate of developing embryos at 10 days post fertilization. Larval behavior (locomotion, visual-motor response, and feeding) was assessed post-hatch in tracked videos with Ethovision. Tissue analysis indicated successful maternal transfer of Hg to eggs in the high Hg feed treatment. Overall, this work contributes to the ongoing development of an ecological modeling framework in a fish with an extensive toxicological and genomic background. Ultimately, we are working to connect molecular mechanistic, physiological, reproductive, and behavioral responses to population level fitness.