Study - Hurricane Harvey Drove Acidity In Galveston Bay Up To 4X Normal, Caused Oyster Dieoff
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Galveston Bay contains a mix of fresh water from rivers and salty seawater from the Gulf of Mexico – oysters’ preferred habitat. We collected water samples in the bay two weeks after Harvey and found that the bay was made up almost entirely of river water and rainwater from the storm. Since rainwater, river water and seawater all have different chemistries, we were able to calculate that rainwater made up almost 50% of the water in the bay. This means that acidic rainwater from Harvey replaced the basic seawater within the bay after the storm. The average bay water pH had dropped from 8 to 7.6, a 2.5-fold increase in acidity. Some zones had pH even as low as 7.4 – four times more acidic than normal.
This extreme acidification lasted for more than three weeks. Bay waters became corrosive not only to more sensitive larval and juvenile oyster shells, but to adult oyster shells as well. Scientists had predicted that increasing CO₂ could cause this scale of coastal acidification but did not expect to see it until around the year 2100.
The fresh water from Harvey also caused a severe oyster die-off in the bay because oysters need slightly salty water to survive. Harvey struck in the middle of oyster spawning season, and acidification may have slowed reef recovery by making it harder for young oysters to form new shells. Officials at the Texas Parks and Wildlife Department have told us that four years later, in late 2021, some Galveston Bay oyster reefs still showed very low additions of new oysters.
Only a few studies, including ours, have analyzed how tropical cyclones affect coastal acidification. In our view, however, it is highly possible that other storms have caused the kind of extreme acidification that we detected in the wake of Harvey. We reviewed the 10 wettest tropical cyclones in the U.S. since 1900 and found that nine, including Harvey, caused large amounts of rain and flooding in coastal areas with bay or estuary ecosystems. Other storms didn’t produce as much rainfall as Harvey, but some of the affected bays were much smaller than Galveston Bay, so less rain would have been needed to replace seawater in the bay and cause a similar level of acidification to what Harvey produced.
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https://theconversation.com/hurricane-harvey-more-than-doubled-the-acidity-of-texas-galveston-bay-threatening-oyster-reefs-196470
