Climate change threatens to reduce marine mollusk sizes

A study published in the Proceedings of the National Academy of Sciences (PNAS) indicates that climate change could significantly alter the size of most marine mollusks by the year 2100. Researchers analyzed over 23,000 species across ten major ocean basins, evaluating how changes in temperature, oxygen levels, and ocean productivity affect various groups, including clams, oysters, snails, squid, and octopuses.

Under high greenhouse gas emission scenarios, the impact is expected to be non-uniform. Approximately two-thirds of the analyzed combinations of mollusk groups and ocean regions are projected to see significant size reductions. While average body length might decrease by up to 16%, the impact on total biomass could be much more severe due to the mathematical relationship between length and mass. For instance, a 16.2% reduction in the average length of clams in the Baltic Sea could result in an approximately 41% drop in average body mass.

Conversely, some species, such as certain cephalopods, might increase in size in specific regions. The researchers warn that these shifts could disrupt marine ecosystem functions, including nutrient cycling, carbon sequestration, and food supplies for human societies.