PARENT SESSION
Organized Oral Session 8: Contaminants in aquatic systems: Individual effects and community consequences.
Organizer(s): J Kerby and R Relyea
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 510b, Level 5, Palais des congrès de Montréal

The role of growth in the transfer of toxins in aquatic food webs.

Karimi, Roxanne^*,1, Folt, Carol¹, ¹ Dartmouth College, Hanover, NH

ABSTRACT- Many fish species obtain both toxins and energy for growth from benthic and pelagic invertebrate prey. We have found that these habitat-specific prey have consistently different mercury (Hg) concentrations. Such variation in Hg among prey types should drive predator Hg accumulation, but variation in predator growth rates from habitat-specific diets may explain the lack of simple correlations in nature. We hypothesized that somatic growth inversely modifies Hg transfer from these two prey sources. To address the roles of growth and diet composition in Hg accumulation in freshwater fish, we examined a bioenergetics-mass balance model under habitat specific diet scenarios with prey Hg concentrations from the field, and prey quality values (cal/g, digestibility) from the literature. We also compared the sensitivity of fish growth and Hg accumulation to prey quantity, prey quality, activity level and temperature in multiple published trophic transfer models. Results suggest that fish specializing on a pelagic diet should have higher Hg burdens than fish consuming littoral-benthic prey, owing largely to zooplankton's high Hg concentration. Our sensitivity analysis found that through their effects on growth, Hg accumulation is highly sensitive to prey quality and quantity, and moderately sensitive to activity level and temperature. These findings highlight the primacy of diet composition and individual growth rates in the trophic transfer and accumulation of toxins and suggest a focus for future empirical investigation.

Key words: benthic-pelagic, trophic transfer, heavy metals, bioenergetics