NEW ORLEANS — Finding crabs for future cookouts in Louisiana could become more difficult if the amount of carbon dioxide being pumped into the atmosphere — which leads to more acidic waters — continues to increase, a Tulane researcher reported Thursday.
Shellfish growers in other parts of the world already have reported problems with getting small oysters to grow a viable shell in the more acidic water, according to research presented at the State of the Coast conference Thursday.
The blue crab has a different makeup, but Tulane University’s Sarah Giltz studied the impact of ocean acidification on the $50 million-a-year Gulf of Mexico blue crab fishery.
To find out, Giltz hatched four batches of blue crab eggs into larvae and put half of each batch in regular seawater and half in seawater at the level of acidification predicted by the Intergovernmental Panel on Climate Change.
She found that blue crab larvae living in the more acidic seawater grew more slowly, had higher mortality rates and were smaller than their counterparts. There also was an unexplained crash in the larvae population in about 40 percent of the tanks used while there was no similar crash in the regular seawater group.
The story was different when Giltz did the same experiment with juvenile blue crabs. In case after case, there was no difference between those growing in regular seawater and the more acidic.
Giltz speculated that because juvenile crabs live in the coastal marshes where the acidity of the water can vary widely and the larvae live in the saltwater offshore, the juveniles have more of an ability to adapt.
Implications of the study are that as carbon dioxide continues to be released and the oceans continue on their way to acidification, the baby blue crabs that depend on the salty Gulf of Mexico could face some challenges in the future, Giltz said.
There still are many questions to be answered through additional research, including why the slower growth in the larvae occurs with more acidic water and what led to the population crashes Giltz saw in the lab.
The State of the Coast Conference is organized by the Coalition to Restore Coastal Louisiana, with help from the state Coastal Protection and Restoration Authority and The Water Institute of the Gulf, to bring together researchers who primarily work on the challenges facing Louisiana’s coast.
These issues include a variety of topics, including coastal land loss and the needs of communities facing natural disasters.
Follow Amy Wold on Twitter, @awold10.