Acid in the Pacific Ocean is literally eating away crabs’ shells

Humans have pumped about 2 trillion tons (1.8 trillion metric tons) of carbon dioxide (CO2) into the atmosphere since the start of the Industrial Revolution, and the ocean has absorbed about 25% of it.

This glut of greenhouse gases not only warms the ocean (contributing to more-frequent heat waves and severe weather), but also changes the water’s chemistry, slowly acidifying it and reducing the concentration of molecular building blocks that shellfish, corals and other marine life use to craft their hard outer shells. According to a new study, that molecular mix-up is already having harmful effects on the development of some baby crabs.

In the new research, published Jan. 22 in the journal Science of the Total Environment, marine scientists funded by the National Oceanic and Atmospheric Administration (NOAA) studied 50 larval Dungeness crabs (Metacarcinus magister) collected from 10 sites near the Pacific coast of the United States and Canada. Overall, crabs collected closer to the coastline, where oceans tend to be more acidic, were in much worse shape than crabs collected farther out a-sea.

The acidification corroded the larvae’s shells, stunted their growth, and, in some cases, damaged or destroyed the animals’ tiny sensory organs known as mechanoreceptors. All in all, the researchers wrote, acidification left larvae smaller, weaker and less likely to survive into maturity.

The condition of these crabs — which are an important source of food for both humans and other marine creatures — should be a wake-up call to the dangers of acidification,  lead study author Nina Bednarsek told