Pre-adaptation through lifestyle and ontogeny?

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 calci-fication rates, metabolic depression and even mortality when being exposed to near-5 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 10 ontogenetic and lifestyle traits that lead to an increased tolerance towards high environmental pCO 2. In general, marine ectothermic metazoans with an extensive extracellu-lar fluid volume may be less vulnerable to future acidification as their cells are already exposed to much higher pCO 2 values (0.1 to 0.4 kPa, 1000 to 4000 µatm) than those of unicellular organisms and gametes, for which the ocean (0.04 kPa, 400 µatm) is the ex-15 tracellular space. A doubling in environmental pCO 2 therefore only represents a 10% change in extracellular pCO 2 in some marine teleosts. High extracellular pCO 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 20 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 extracel-lular space. These ion-transport systems, which are located in highly developed gill epithelia, form the basis for efficient compensation of pH disturbances during exposure 25 to elevated environmental pCO 2. Compensation of extracellular acid-base status in turn may be extremely important in avoiding metabolic depression. So far, maintained " performance " at higher seawater pCO 2 (>0.3 to 0.6 kPa) has only been observed in 4694 Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion adults/juveniles of active, high metabolic species with a powerful ion regulatory apparatus. However, while some of these taxa are adapted to cope with elevated pCO 2 during their regular …