Humboldt Bay a refuge from ocean acidification, but for how long?

Research has found that while eelgrass provides a buffer from ocean acidification, it does not help oysters grow any faster. (Audubon California — Contributed)

Growing oysters in beds of eelgrass won’t help them grow faster even though eelgrass acts as a buffer against the ocean acidification that makes it more difficult for juvenile oysters to form shells and develop in their larval state.

Joe Tyburczy, a marine ecologist with California Sea Grant Extension, a statewide collaboration between government agencies and universities focused on coastal and marine science, has been studying eelgrass and its impact on buffering ocean acidification in Humboldt Bay. Tyburczy’s research revealed oysters grown outside of eelgrass beds actually grow faster than ones grown in eelgrass, “which we think may have more to do with flow which is restricted by eelgrass.”

“The faster the flow, the more food delivered to these guys,” Tyburczy told a group of about 20 at a talk at the Humboldt State University Natural History Museum in Arcata on Thursday night. “So whatever chemical benefit there is may be outweighed by getting less food if you’re in an eelgrass bed.”

As the ocean becomes more acidic, “the amount of carbonate (in the ocean) drops precipitously,” Tyburczy said.

“That is a real problem for calcifying organisms because carbonate is what they build their shell from,” he said.

Ocean carbonate chemistry has already changed significantly since the oceans have absorbed “93% of the extra energy from the enhanced greenhouse effect and approximately 30% of anthropogenic carbon dioxide,” according to the Ocean Chapter of the Intergovernmental Panel on Climate Change’s report “Climate Change 2014: Impacts, Adaptation, and Vulnerability.”

This presents a problem for the oyster industry, which is particularly large in Humboldt Bay, generating $9.8 million in revenue in 2016, according to a 2018 summary report of a survey Sea Grant and Humboldt State University did of the Humboldt Bay shellfish mariculture business.

The Humboldt County oyster industry supplies an estimated 70% of California’s oysters and is one of the two largest regions for mariculture production, along with Tomales Bay, according to the survey summary.

Local oyster farmer Sebastian Elrite said he isn’t too worried about the situation at the moment because the industry is developing techniques to counteract the impacts of ocean acidification.

“I think there’s going to be some hills and valleys, but with some good science and that kind of stuff we should be able to conquer this,” Elrite said.

At the moment, even with the buffering from the eelgrass and other photosynthesizing species, Tyburczy said “it’s still not good enough to be conducive to growing oysters in the hatchery.”

As a result of this research, the Hog Island Oyster Company’s hatchery has set up a system to add sodium carbonate to make it more hospitable for the oysters trying to grow there, he said.

Hog Island Oyster Company was unavailable for comment by publication time.

But the ocean is only expected to acidify further, though the rate at which it acidifies will vary from region to region.

Eelgrass is definitely buffering Humboldt Bay from the impacts of ocean acidification, but Tyburczy said it’s still hard to say by how much.

Humboldt Bay is likely to remain a refuge from acidification to some degree Tyburczy said, but “it’s capacity to do that isn’t unlimited.”

In order to really get ahead of the problem, Tyburczy said it will be important to start tackling climate change more aggressively.

“The situation is definitely dire,” Tyburczy said, “but it’s not hopeless.”

Sonia Waraich, Times Standard, 16 February 2020. Article.

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