Journal
JOURNAL OF EXPERIMENTAL BIOLOGY
Volume 223, Issue 16, Pages -Publisher
COMPANY BIOLOGISTS LTD
DOI: 10.1242/jeb.224444
Keywords
Climate change; Cross-tolerance; Eutrophication; Multiple stressors; Plasticity; Swimming performance
Categories
Funding
- Australian Government's National Environmental Science Program through the Threatened Species Recovery Hub [3.3.7]
- Threatened Species Recovery Hub PhD support fund
- Australian Government Research Training Program (RTP) Scholarship
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Rising temperatures are set to imperil freshwater fishes as climate change ensues unless compensatory strategies are employed. However, the presence of additional stressors, such as elevated nitrate concentrations, may affect the efficacy of compensatory responses. Here, juvenile silver perch (Bidyanus bidyanus) were exposed to current-day summer temperatures (28 degrees C) or a future climate-warming scenario (32 degrees C) and simultaneously exposed to one of three ecologically relevant nitrate concentrations (0, 50 or 100 mg l(-1)). We measured indicators of fish performance (growth, swimming), aerobic scope (AS) and upper thermal tolerance (CTmax) to test the hypothesis that nitrate exposure would increase susceptibility to elevated temperatures and limit thermal compensatory responses. After 8 weeks of acclimation, the thermal sensitivity and plasticity of AS and swimming performance were tested at three test temperatures (28, 32, 36 degrees C). The AS of 28 degrees C-acclimated fish declined with increasing temperature, and the effect was more pronounced in nitrate-exposed individuals. In these fish, declines in AS corresponded with poorer swimming performance and a 0.8 degrees C decrease in CTmax compared with unexposed fish. In contrast, acclimation to 32 degrees C masked the effects of nitrate; fish acclimated to 32 degrees C displayed a thermally insensitive phenotype whereby locomotor performance remained unchanged, AS was maintained and CTmax was increased by 1 degrees C irrespective of nitrate treatment compared with fish acclimated to 28 degrees C. However, growth was markedly reduced in 32 degrees C-acclimated compared with 28 degrees C-acclimated fish. Our results indicate that nitrate exposure increases the susceptibility of fish to acute high temperatures, but thermal compensation can override some of these potentially detrimental effects.
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