Can Food Limitation Increase Resilience to Elevated pCO2 and Temperature?

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.