Table 1.

Summary of probable main effects of future ocean acidification on different groups of marine organisms, mostly based on experimental studies.

groupmain acidification impacts
warm-water coralsa relatively well-studied group. The great majority of experiments show that increasing seawater CO2 decreases adult coral calcification and growth, and suppresses larval metabolism and metamorphosis [14,52,53]. Although most warm-water coral reefs will remain in saturated waters by 2100, saturation levels are predicted to decline rapidly and substantially; thus, coral calcification is unlikely to keep up with natural bioerosion [22,31,32,54,55]. Interactions with other climatic and anthropogenic pressures give cause for concern [56,57]
cold-water coralsthe long-lived nature of cold-water corals, and their proximity to aragonite saturation horizons, makes them vulnerable to future shoaling of the ASH. Approximately 70% of known cold-water coral locations are estimated to be in undersaturated waters by the end of this century [25,27]. Experiments found the effect of pH change on calcification was stronger for fast growing, young polyps [28]
molluscssignificant effects on growth, immune response and larval survival of some bivalves [5860], although with high inter-specific variability [6163]. Pteropods seem particularly sensitive [8,64,65] and are a key component of high latitude food webs. Molluscs are important in aquaculture, and provide a small yet significant protein contribution to the human diet [66]
echinodermsjuvenile life stages, egg fertilization and early development can be highly vulnerable, resulting in much reduced survival [6769]. Adult echinoderms may increase growth and calcification; such responses are, however, highly species-specific [45]
crustaceansthe relative insensitivity of crustaceans to ocean acidification [47,70,71] has been ascribed to well-developed ion transport regulation and high protein content of their exoskeletons [43]. Nevertheless, spider crabs show a narrowing of their range of thermal tolerance by approximately 2°C under high CO2 conditions [72]
foraminiferashell weight sensitive to Embedded Image decrease in the laboratory [73] with field evidence for recent shell thinning [21,74]
fishadult marine fish are generally tolerant of high CO2 conditions [51,75,76]. Responses by juveniles and larvae include diminished olfactory and auditory ability, affecting predator detection and homing ability in coral reef fish [7779], reduced aerobic scope [80] and enhanced otolith growth in sea bass [81]
coralline algaemeta-analysis [43] showed significant reductions in photosynthesis and growth due to ocean acidification treatments. Elevated temperatures (+3°C) may greatly increase negative impacts [82]. Field data at natural CO2 vents show sensitivity of epibiont coralline algae [83,84]
non-calcified macro-algae; sea grassesboth groups show capability for increased growth [42,43]. At a natural CO2 enrichment site, sea grass production was highest at mean pH of 7.6 [83]
coccolithophoresmost studies have shown reduced calcification in higher CO2 seawater, as first found by [85]. However, the opposite effect has also been reported [86], and ocean acidification impacts on coccolithophore photosynthesis and growth are equivocal, even within the same species. This variability may be due to the use of different strains [87], experimental conditions [88] and species-specific sensitivities to different carbonate chemistry parameters [49]
bacteriamost cyanobacteria (including Trichodesmium, a nitrogen-fixer) show enhanced photosynthesis and growth under increased CO2 and decreased pH conditions [89,90]. Heterotrophic bacteria investigated to date show many responses with potential biogeochemical significance, including decreased nitrification and increased production of transparent exopolymer particles (affecting aggregation of other biogenic material and its sinking rate) [44]. Adaptation to a high CO2 world is likely to be more rapid by bacteria and other short-generation microbes than by multicellular organisms [10]