Physiological basis for high CO 2 tolerance in marine ectothermic animals: pre-adaptation through lifestyle and ontogeny?

• Main Authors: M. Bleich, M. C. Thorndyke, M. Lucassen, S. Dupont, M. Langenbuch, M. A. Gutowska, F. Melzner, H.-O. Pörtner
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2009
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Ocean acidification
• Online Access: https://doaj.org/article/2ecd7c99de054bb4bf8713931e32386d

Future ocean acidification has the potential to adversely affect many marine organisms. A growing body of evidence suggests that many species could suffer from reduced fertilization success, decreases in larval- and adult growth rates, reduced calcification rates, and even mortality when being exposed to near-future levels (year 2100 scenarios) of ocean acidification. Little research focus is currently placed on those organisms/taxa that might be less vulnerable to the anticipated changes in ocean chemistry; this is unfortunate, as the comparison of more vulnerable to more tolerant physiotypes could provide us with those physiological traits that are crucial for ecological success in a future ocean. Here, we attempt to summarize some ontogenetic and lifestyle traits that lead to an increased tolerance towards high environmental p CO 2 . In general, marine ectothermic metazoans with an extensive extracellular fluid volume may be less vulnerable to future acidification as their cells are already exposed to much higher p CO 2 values (0.1 to 0.4 kPa, ca. 1000 to 3900 μatm) than those of unicellular organisms and gametes, for which the ocean (0.04 kPa, ca. 400 μatm) is the extracellular space. A doubling in environmental p CO 2 therefore only represents a 10% change in extracellular p CO 2 in some marine teleosts. High extracellular p CO 2 values are to some degree related to high metabolic rates, as diffusion gradients need to be high in order to excrete an amount of CO 2 that is directly proportional to the amount of O 2 consumed. In active metazoans, such as teleost fish, cephalopods and many brachyuran crustaceans, exercise induced increases in metabolic rate require an efficient ion-regulatory machinery for CO 2 excretion and acid-base regulation, especially when anaerobic metabolism is involved and metabolic protons leak into the extracellular space. These ion-transport systems, which are located in highly developed gill epithelia, form the basis for efficient compensation of pH disturbances during exposure to ...