| Autor: |
Montgomery DW; Bioscience Department, College of Life and Environmental Sciences, University of Exeter, Exeter, UK. dm513@exeter.ac.uk., Simpson SD; Bioscience Department, College of Life and Environmental Sciences, University of Exeter, Exeter, UK., Engelhard GH; Centre for Environment, Fisheries & Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT, UK.; School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK., Birchenough SNR; Centre for Environment, Fisheries & Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT, UK., Wilson RW; Bioscience Department, College of Life and Environmental Sciences, University of Exeter, Exeter, UK. R.W.Wilson@exeter.ac.uk. |
| Abstrakt: |
Global environmental change is increasing hypoxia in aquatic ecosystems. During hypoxic events, bacterial respiration causes an increase in carbon dioxide (CO 2 ) while oxygen (O 2 ) declines. This is rarely accounted for when assessing hypoxia tolerances of aquatic organisms. We investigated the impact of environmentally realistic increases in CO 2 on responses to hypoxia in European sea bass (Dicentrarchus labrax). We conducted a critical oxygen (O 2crit ) test, a common measure of hypoxia tolerance, using two treatments in which O 2 levels were reduced with constant ambient CO 2 levels (~530 µatm), or with reciprocal increases in CO 2 (rising to ~2,500 µatm). We also assessed blood acid-base chemistry and haemoglobin-O 2 binding affinity of sea bass in hypoxic conditions with ambient (~650 μatm) or raised CO 2 (~1770 μatm) levels. Sea bass exhibited greater hypoxia tolerance (~20% reduced O 2crit ), associated with increased haemoglobin-O 2 affinity (~32% fall in P 50 ) of red blood cells, when exposed to reciprocal changes in O 2 and CO 2 . This indicates that rising CO 2 which accompanies environmental hypoxia facilitates increased O 2 uptake by the blood in low O 2 conditions, enhancing hypoxia tolerance. We recommend that when impacts of hypoxia on aquatic organisms are assessed, due consideration is given to associated environmental increases in CO 2 . |
