Growth of the estuarine fish Fundulus heteroclitus in response to diel-cycling hypoxia and acidification: interaction with temperature

Growth rate of Fundulus heteroclitus was examined at 25 and 30 degrees C in nine treatments of diel-cycling dissolved oxygen (DO) and pH. Extreme diel-cycling DO (1-11 mg O2.L-1) negatively impacted growth during 10 days at 30 degrees C, but not at 25 degrees C. Moderate DO cycles (3-9 mg O2.L-1) had no direct growth impact at either temperature. Fish did not appear to acclimate, during days 10-30, to the initial growth-limiting effects of extreme diel DO cycles at 30 degrees C. Diel-cycling DO interacts synergistically with temperature to impact growth. There was no evidence of an independent growth effect of either moderate pH cycles (7.2-7.8) or extreme pH cycles (6.8-8.1) at either temperature. Mean low pCO(2) levels in extreme cycles were similar to 32 000 and similar to 47 000 mu atm at 25 and 30 degrees C, respectively. It is noteworthy that these high mean nightly pCO(2) levels are more than an order of magnitude higher than the chronic mean oceanic pCO(2) of similar to 1000 mu atm projected by the year 2100.