Meeting Abstract
Tannins comprise a large class of natural compounds that are produced by plants for defensive purposes. A variety of forms accumulate in large quantities in plant tissue, after which they move throughout ecological systems when plants decay or are consumed by animals. In many aquatic systems, such as the boreal lakes inhabited by threespine stickleback, tannins may reach very high levels when plants decay each spring, and the presence of tannins in the aquatic environment is considered to be harmful to aquatic life. However, the specific effects of tannins on aquatic organisms, especially on fish, remain unclear. We examined the effect of tannins on aerobic capacity by estimating the prolonged swimming stamina of individual stickleback with a commonly used assay. Further, we framed our study within an evolutionary context by testing fish from each of three populations that we predicted would have become adapted to the natural tannin levels in their environments—ancestral marine stickleback; stickleback from a very low-tannin lake; and stickleback from a very high tannin lake. Embryos from wild-caught parents were raised for one year in laboratory tanks with negligible tannin levels. When fish reached 1 year of age, they were given the performance assay, after which they were held in water containing a moderate amount of tannins. Individually identifiable fish were tested every two days for the next two weeks. Performance was analyzed via a repeated measures design. Population, the repeated measure (days of exposure), and their interaction were all significant, with population and the interaction having substantial effect sizes. Results generally corresponded to expectations, with fish from the high-tannin lake performing best overall, and showing the least decline in performance with time.
