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San Diego Bay Area oysters are dying of herpesvirus because of ‘warmer waters’
Yep, oysters with herpes. Once more, with feeling: oysters. With herpes. In San Diego Bay. Higher water temperatures appear to be killing young Pacific oysters, or rather, allowing a strain of herpesvirus to kill them. Fortunately, the ostreid herpesvirus, or OsHV-1, doesnt pose a threat to humans, so its not panic stations. But oyster farms are being disrupted.
Its time to discuss oysters with herpes, or more specifically, the relationship between rising water temperatures and the spread of a deadly virus that infects Pacific oysters. Thats the purview of a recent study into the phenomenon. Its lead author, Emily Kunselman, says food security and ocean sustainability are dependent on aquaculture, of which oyster farms are a prime example.
Pacific oysters are dying in droves of herpesvirus as ocean temperatures rise
Kunselmen and her team found that a variant of the ostreid herpesvirus extant in the San Diego Bay Area does particularly well in temperatures above 59�F (15�C).
It causes oyster mortality meaning it kills them starting at 64�F (18�C). The higher the water temperature, the faster the oysters die. The worst temperatures appear to be between 70 and 75�F (21-24�C).
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Warmer waters weaken the oysters defenses, knock their microbiomes out of kilter, and lead to potential bacterial infections, according to the papers literature review which is basically a roundup of what researchers already know about the topic.
This is a serious concern for oyster farmers in and around San Diego, who have to contend with water temperatures in the range of 59�F (15�C) in winter to more than 71.6�F (22�C) in summer.
In 2018, when OsHV-1 was first detected in the area, seawater temperatures climbed to 79�F (26�C). In anything above 70�F (21�C), the virus replicates in oyster tissues to an extent that is deadly, and rapidly accelerates oyster deaths, killing them in a matter of days.
What does this mean for everyday Americans?
If rising seawater temperatures allow this particular strain of herpesvirus to thrive and kill oyster populations in the San Diego Bay Area, the most obvious human victims are the people farming the oysters in the local area. And, of course, Californian oyster fans, who may have to resort to imported, less-than-fresh oysters. No one likes less-than-fresh oysters.
But co-author Colleen Burge emphasizes that understanding temperature thresholds will help protect both wild and cultured shellfish in the state of California and beyond, per the Scripps Institution of Oceanographys press release.
In other words, other marine life could be at risk, and this will have broader ramifications for ecosystem stability and health. On human lives, too, further down the line.
Previously, we’ve written about the effects climate change has had and could continue to have, on the levels of dangerous bacteria in seafood. That was in response to a report by the European Food Safety Authority into the impact of global warming on the bacteria Vibrio, which is notorious for its resistance to last-resort antibiotics.
The good news is that OsHV-1 doesnt appear to affect wild oysters. They seem to be tolerant of the virus, which has kept viral levels below the limit of detection.
Aquaculture, of which oyster farms are an example, is essential to both food security and ocean sustainability, Kunselman adds.
Oysters are remarkable creatures that filter the water, keep things clean, and support thriving ecosystems. [&] By managing and mitigating some of the challenges presented in our study, there are opportunities to see aquaculture flourish.
