Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $7,925 Total Non-Federal Funds: $10,552
Principal Investigators: Richard D. Durtsche
Abstract: The projected climate change and increase in thermal conditions over the next 50 years has the potential to alter the metabolic scope and potential fitness of aquatic ectotherms in Kentucky. This study experimentally tests if elevated egg incubation temperature affects metabolic scopes of juvenile fish of three species from three different strata in Kentucky streams. The bottom-dwelling rainbow darter Etheostoma caeruleum has a spring reproductive season, March â€“ May, the midwater bluntnose minnow Pimephales notatus have a late spring/early summer reproductive system, May â€“ June, and the top water mosquito fish Gambusia affinis has a summer reproductive system, June â€“ August. Cohorts of each fish species will be raised through embryogenesis until they can feed exogenously in either natural river temperatures (historical average) or in elevated (+ 3ËšC, climate change) temperatures. The standard (resting) metabolic rate (Ms), their active (maximum) metabolic rate (Mmax), and the absolute aerobic scope (AS = Mmax â€“ Ms) of juveniles from both incubation temperatures will be then tested at 13ËšC, 18ËšC, 23ËšC, and 28ËšC. We will also run tests at adults of each species that have been acclimated at each of these temperatures. We will use our findings to determine at which temperatures these fish have decreased metabolic scope, and therefore decreased fitness. These results can then be compared with long term data sets of stream temperatures from USGS river monitoring stations to determine how frequently these fish could have encounter these temperatures of low performance in the past (especially during reproduction and egg development periods) and what they may be like in the future is climate change elevates stream temperatures. Moreover, these data will be useful to inform managers as to what times and how often dam waters could be released to reduce stress temperatures on fish and other aquatic organisms in Kentucky rivers. In addition, the results of this experiment will test the countergradient variation hypothesis (CGV) to determine if variation in metabolic rates, is inversely related to changing thermal conditions. While previous studies have related CGV to genetic differences between populations, this study could show that thermal differences encountered at the embryonic stage can produce a phenotypic pattern consistent with CGV. It is difficult to predict the consequences of these metabolic changes in a future warmer climate, as lower metabolic rates indicate that fish will probably expend less energy, but a reduced aerobic or metabolic scope may counteract this affect, limiting the foraging ability of fish and their escape from predators.