Chair: Cliff Law
Samuel P.S. Rastrick1, Jiang Zengjie2, Helen E Graham3, Anette Olafsen1, Cathinka Krogness1, Tore Strohmeier1, Øivind Strand1
1) Institute of Marine Research, PO Box 1870 Nordness, 5870 Bergen, Norway
2) Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences
106 Nanjing Road, Qingdao City, Shandong Province, China
3) Uni Research Environment, Postboks 7810, 5020 Bergen, Norway.
Elevated costs of maintaining homeostasis under elevated pCO2 and temperature conditions has been shown to divert energy away from growth and reproduction effecting the function and fitness of marine species. Although these energetic trade- offs have been well demonstrated few studies have investigated how these are affected by changes in the total amount of energy available through feeding. It has been postulated that limited access to food may lower energy availability and increase sensitivity. However, in response to food limitation some suspension feeders such as the invasive tunicate Ciona intestinalis are able to increase clearance rate and absorption efficiency whilst reducing metabolic demand resulting in the maintenance or even elevation of overall energy absorption.
We demonstrate that when C. intestinalis are exposed to elevated pCO2 (750µatm) or temperature (15°C) for 1 month comparatively higher clearance rates, absorption efficiencies, and reduced metabolic demand in response to food limitation actually increases scope for growth and decreases mortality in food limited treatments (filtered seawater), compared to treatments supplied with natural seawater seston. In addition, 1 month acclimation of C. Intestinalis to a range of temperatures (7 to 17°C) demonstrate that maximum aerobic temperatures are lower (15°C) in naturally fed compared with food limited individuals (>17°C) possibly due to depressed metabolic demand enabling higher temperatures to be reached before exceeding aerobic scope and oxygen transport capacity. However this response to food limitation cannot be maintained when elevated temperature and pCO2 are combined (750µatm/15°C). Together these experiments demonstrate that in some species responses to food limitation may increase resilience to elevated pCO2 and temperature, at least as individual stressors. In addition this work demonstrates the complexity and importance of studying feeding responses in determining the future sensitivity of marine species to both ocean warming and acidification.