Interactive effects of diel-cycling hypoxia, pH, and temperature on growth of Fundulus heteroclitus, a common estuary-resident fish

Bogue, Katherine
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University of Delaware
Growth rate (GS) of Fundulus heteroclitus was examined at three temperatures in several treatments of diel-cycling DO and pH. Diel-cycling pH (ranging either from 7.2-7.8 or 6.8-8.1) at 25°, 30° and 35°C did not significantly affect growth. However, wide ranging diel cycles in DO (1-11 mg O2 l-1 but not 3-9 mg O2 l-1) significantly reduced growth rates during initial 10 days of treatment at 30°C but not at 25°C. Rising temperature appears to determine whether diel-cycling DO significantly impacts growth rates of this species. F. heteroclitus acclimated to treatment conditions after 10 days, with initial differences in growth rate between treatments and control disappearing. In a separate experiment, F. heteroclitus did not show a statistically significant level of growth compensation when fish exposed to 10 days of treatment (1-11 mg O2 l-1, 6.8-8.1 pH) were returned to normoxia and control pH. However, the high level of individual growth variation following return to normoxia and control pH makes a definitive conclusion on growth compensation difficult.
Diel-cycling , Hypoxia , pH , Fundulus heteroclitus