The Pacific Ocean Is So Acidic That Crab Shells Are Dissolving

James Marshall
February 1, 2020

The Pacific Ocean is becoming more acidic, and the cash-crabs that live in its coastal waters are some of its first inhabitants to feel its effects. The agency studies ocean acidification and how changing pH levels are impacting coasts. Lower pH levels in the ocean waters are causing parts of the Dungeness crab shells to dissolve.

The shells of the crabs also help them regulate their buoyancy in the Pacific Ocean or in the water. While the results aren't unexpected, the research's authors stated the harm to the crabs is premature: The acidity wasn't anticipated to damage the crabs this quickly. Researchers say it is a warning for the future of seafood and the health of marine life.

"If the crabs are affected already, we really need to make sure we pay much more attention to various components of the food chain before it is too late", said study lead author Nina Bednarsek, a senior scientist with the Southern California Coastal Water Research Project.

A study by the National Oceanic and Atmospheric Association (NOAA) reports that the acid level in the Pacific Ocean is rapidly increasing.

The NOAA says the Dungeness crab is a prized crustacean that supports the most valuable fishery on the west coast. They are also important to tribal and recreational crabbers.

Coastal habitats with the steepest ocean acidification gradients are most detrimental for larval Dungeness crabs. The primary cause is an increase in absorption of atmospheric Carbon dioxide over a long period. NOAA explains that when Carbon dioxide is absorbed by seawater, a chain of chemical reactions is set in motion. Increased acid level causes crab shells to melt.

The animals that we listed above rely on the same carbonate ions to build structures such as shells. In the absence of enough carbonates, it becomes hard for crabs, oysters, and clams to build shells.

Scientists have observed damage due to corrosive water in species other than crab in recent years, but the Dungeness finding is unusual, said Chris Harley, a professor of zoology at UBC.

"We found dissolution influences to the crab larvae that were no longer seen to happen until later on this century", said Richard Feely, study co-author, and NOAA senior scientist. Crabs without these tiny mechanoreceptors could move slowly and have trouble swimming and finding food, according to CNN. This could mean developmental delays that might mess with their charge of maturation.

"We have seen this in the lab in oysters, mussels and abalone, and we know that the larval stage is really sensitive", he said.

It's not clear if the same forces could negatively impact adult Dungeness crabs, a question that requires more research.

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