Physiological responses and scope for growth upon medium-term exposure to the combined effects of ocean acidification and temperature in a subtidal scavenger Nassarius conoidalis

Physiological responses (ingestion rate, absorption rate and efficiency, respiration, rate, excretion rate) and scope for growth of a subtidal scavenging gastropod Nassarius conoidalis under the combined effects of ocean acidification (pCO₂ levels: 380, 950, 1250μatm) and temperature (15, 30°C) were investigated for 31 days. There was a significant reduction in all the physiological rates and scope for growth following short-term exposure (1-3 days) to elevated pCO₂ except absorption efficiency at 15°C and 30°C, and respiration rate and excretion rate at 15°C. The percentage change in the physiological rates ranged from 0% to 90% at 15°C and from 0% to 73% at 30°C when pCO₂ was increased from 380μatm to 1250μatm. The effect of pCO₂ on the physiological rates was enhanced at high temperature for ingestion, absorption, respiration and excretion. When the exposure period was extended to 31 days, the effect of pCO₂ was significant on the ingestion rate only. All the physiological rates remained unchanged when temperature increased from 24°C to 30°C but the rates at 15°C were significantly lower, irrespective of the duration of exposure. Our data suggested that a medium-term exposure to ocean acidification has no effect on the energetics of N.conoidalis. Nevertheless, the situation may be complicated by a longer term of exposure and/or a reduction in salinity in a warming world.