Shellfish such as clams, crabs and oysters need tiny building blocks called calcium carbonate ions to grow and thrive.
These particles are essential to build sturdy shells that protect marine creatures from predators – and make them more appealing for human diners.
But rising acidity tied to climate change is making it harder for shellfish to access those fundamental building blocks.
The issue caught officials’ attention in the late 2000s when acidic corrosion caused mass die-offs of baby oysters in the Pacific Northwest.
Researchers at William & Mary’s Batten School and Virginia Institute of Marine Science have teamed up with local shellfish farmers to learn more about how changing conditions could impact the aquaculture industry in coastal Virginia.
“We know the threat exists,” said Emily Rivest, an associate professor in ecosystem health at the Batten School and VIMS. “This gives us the opportunity to try to get ahead of it to understand how to build our resilience and prevent those kinds of dramatic negative impacts.”
The project is funded by a $1.2 million grant from the National Oceanic and Atmospheric Administration’s Ocean Acidification Program.
The ocean absorbs about a third of the climate-warming carbon dioxide humans release into the atmosphere. That causes a cascade of chemical changes underwater, including reducing pH levels.
For millions of years, the ocean’s pH remained relatively stable at 8.2 on the pH scale, which ranges to 14, the most basic. Since the start of the Industrial Revolution, it has dropped to 8.1. Because the scale is logarithmic, that represents a nearly 30% increase in acidity, according to NOAA.
In much of the Chesapeake Bay, the rate of change is happening even more quickly, particularly in the middle, VIMS previously found.
One factor is freshwater. When freshwater surges into the bay, it lowers the amount of salt in the water, which makes it more susceptible to acidity, Rivest said. That has sometimes affected restored oyster reefs on the western side of the Eastern Shore.
Pollution from nutrients washing off land into the bay compounds the issue by triggering algae that produce carbon dioxide when eaten by bacteria, Rivest said.
Luckily, natural variability in the Chesapeake Bay “has shaped the eastern oyster to be a very tough and resilient species,” Rivest said.
Lab tests indicate local oysters are “much more tolerant of acidification” than out West. The question is: What is their breaking point?
Rivest said the only way to find out is to hear what’s happening on the ground, such as at Lambert Shellfish on the Eastern Shore.
Alex Lambert launched the oyster business in 2019 after leaving his accounting job in Washington, D.C.
His parents had a retirement home in Machipongo and Lambert tried his hand at raising oysters along their shoreline. Eventually, he went all in, buying gear and getting permits.
His farm was one of the first in the region to use a “longline” system developed in Australia that uses mesh baskets clipped onto lines suspended above the tidal waterline, instead of floating cages.
Lambert said he quickly learned about several stressors on oysters outside of his control, such as weather and water quality.
Acidification is another topic he hopes to learn more about. A few years ago, he read about the previous die-offs in the Pacific Northwest and thought, “That sounds pretty horrifying.”
Because of different ocean dynamics, it seemed the East Coast might not be as vulnerable. But joining the VIMS project made him want to pay attention.
“We still have the same carbon dioxide in the atmosphere, and that's still being absorbed from the water,” Lambert said.
He also connects it to what he’d been told by other watermen years ago, that Virginia oysters were becoming too brittle and easy to break.
“While it's not wiping out our hatcheries right now, or maybe ever, it probably is impacting the shell strength,” Lambert said. “And if it gets worse in the future, coupled with rising temperatures and lower oxygen, that could potentially be devastating to farms.”
Rivest said researchers are trying to investigate the nuances of the issue.
Adult oysters growing at a farm might be resilient to environmental stress, for example. But larvae raised at the hatchery are more sensitive, and if farmers buy seed affected by acidification, that impacts their future yield.
There are ways for the industry to adapt, such as breeding oysters more tolerant to acidity, she said. Some hatcheries now use a buffering agent to stabilize the water’s pH.
Scientists are also looking into strategies such as removing carbon dioxide from the water or enhancing alkalinity.
As part of the grant project, VIMS plans to develop an online map dashboard allowing growers and officials to look at current and projected water conditions.
Lambert said that could help inform where he decides to invest.
“That's always in the back of my head, where would we go next if we were to expand. So this is a pretty relevant topic.”
