Physiological advantages of dwarfing in surviving extinctions in high-CO2 oceans

Excessive CO2 in the present-day ocean–atmosphere system
is causing ocean acidification, and is likely to cause a severe
biodiversity decline in the future1, mirroring e ects in many
past mass extinctions2–4. Fossil records demonstrate that
organisms surviving such eventswere often smaller than those
before5,6, a phenomenon called the Lilliput e ect7. Here, we
showthat two gastropod species adapted to acidified seawater
at shallow-water CO2 seeps were smaller than those found
in normal pH conditions and had higher mass-specific energy
consumption but significantly lower whole-animal metabolic
energy demand. These physiological changes allowed the
animals to maintain calcification and to partially repair shell
dissolution. These observations of the long-term chronic
e ects of increased CO2 levels forewarn of changes we can
expect in marine ecosystems as CO2 emissions continue to rise
unchecked, and support the hypothesis that ocean acidification
contributed to past extinction events. The ability to adapt
through dwarfing can confer physiological advantages as the
rate of CO2 emissions continues to increase.