Effects of Acclimation Temperature on Responses of Blackfoot Pāua ( Haliotis iris ) to Acute Temperature Change, Reduced Salinity and Progressive Hypoxia

Abstract

Rocky shore haliotids are frequently exposed to significant environmental fluctuations in temperature, salinity and dissolved oxygen. We investigated how acclimation temperature influenced the physiological and biological responses of blackfoot Pāua ( Haliotis iris ) to acute temperature change, reduced salinity and progressive hypoxia. Individuals were acclimated to one of four constant temperatures (12, 15, 18 or 21 °C) for 2 weeks before exposure to four acute temperatures (12, 15, 18 and 21 °C). In the salinity experiment, Pāua were acclimated to three constant temperatures (12, 15 or 18 °C) and then exposed to stepwise lowered salinity from 34‰ to 22‰. Pāua in the hypoxia experiment were acclimated to either 15 or 18 °C and then exposed to progressive hypoxia at four acute temperatures. Oxygen uptake and heart rate increased at higher exposure temperatures, while decreased with reducing salinity. During hypoxia, oxygen uptake was the highest in well‐oxygenated water and rates declined slowly to a critical level. Pāua have a limited ability to acclimate to temperatures above 18 °C and are more stressed by combinations of stressors than individual ones. Pāua are sensitive to environmental changes and they would be vulnerable to increased seawater conditions associated with global warming. These findings improve understanding of Pāua responses to warming, salinity and declined oxygen fluctuations, with implications for aquaculture, fisheries management and conservation under climate change.

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