San Francisco, CA

San Francisco scientists ‘found a cure’ for serious climate change symptom in groundbreaking research

Jano le Roux

Eelgrass, a plant that develops in “underwater meadows” along the California coast and emerges like a floating blanket at low tide, is now considered to be a vital refuge for fish, birds, and juvenile Dungeness crabs. It points out that it will also reduce the acidity of seawater to pre-industrial amounts, providing safe havens for species that can’t stand the effects of climate change.

The UC Davis Bodega Marine Laboratory announced the results of a six-year thesis on Wednesday. The study found that eelgrass meadows in seven California locations reduced ocean acidity by up to 30%. Since acidification has risen by 30% as a consequence of climate change, the plant has the potential to mitigate the impact of its ecosystem. Acidification is the result of the ocean collecting rising levels of carbon dioxide from the environment.

The research, which was reported in the journal Climate Change Biology, is the most detailed to date on seagrass’ potential to reduce ocean acidification over time. Its authors claim that it demonstrates the value of maintaining seagrass meadows, which have declined in amount and size due to contamination and growth around the world so that they can sustain biodiversity as well as farmed oysters, mussels, and abalone harvest.

I’d like this report to help more seagrass conservation projects because these structures are on the decline in many places around the world, said lead author Aurora M. Ricart of the Bigelow Laboratory for Ocean Sciences in Maine, who was doing postdoctoral research at the Bodega Marine Lab during the review.

Ricart and her co-authors used underwater sensors to monitor pH, salinity, temperature, and other conditions in eelgrass beds at Bodega Harbor, Tomales Bay, Elkhorn Slough near Monterey, Newport Bay in Orange County, and Mission Bay in San Diego from 2014 to 2019. By absorbing biomass, the eelgrass beds buffered — or decreased — acidification for an average of 65 percent of the time around the sites.

On the West Coast, eelgrass is the most common species of seagrass. Since ocean acidification decreases young shellfish’s capacity to add calcium carbonate, which they use to create shells, the ability to reduce acidity could support commercial fisheries.

Acidification destroyed millions of oyster larvae in Pacific Northwest farms between 2005 and 2009, prompting farmers to search for new supplies. However, since oyster beds can’t be built directly on top of eelgrass meadows, the next step would be to figure out how to get the buffering effects downstream.

Scientists also understood that eelgrass absorbs carbon dioxide and thereby decreases acidity in the water, but they were skeptical that the results would last, according to Melissa Ward, a study co-author and postdoctoral researcher at San Diego State University.

It’s so cool to be able to illustrate that it’s not a matter of hours, but weeks.

Ward explained that they selected a variety of study sites, including urban harbors as well as more rural, protected areas. The influence of eelgrass on ocean acidity, on the other hand, did not show a significant difference. Also, since plants consume more carbon throughout the day while they photosynthesize, the scientists expected the impact to diminish as night fell. Rather, it went on late into the night.

Eelgrass meadows are now known to avoid deforestation and provide shelter for seabirds, as well as salmon and halibut, as well as a rookery for Dungeness crab and spiny lobster, all of which fail to grow shells in acidic waters.

“Some critical species will seek refuge in the seagrass nooks and crannies when they’re more vulnerable during their early life history stages,” said Rebecca Albright, curator at the California Academy of Sciences, who has observed the impact of ocean acidification on coral reefs but was not included in the research. “Their ability to buffer acidification would make them an even more valuable refuge, especially for those crustaceans.”

The state has also taken steps to safeguard its eelgrass ecosystem. By 2025, the California Ocean Conservation Council aims to maintain the state’s current 15,000 acres of seagrass beds while simultaneously creating 1,000 acres.

Projects like the ones Beheshti is working on have the advantage of allowing local municipalities to tackle the impacts of climate change even though they lack the ability to reduce the global pollution that is driving it, according to Ward.

Photo credits:

Photo by Thomas Peham on Unsplash

Photo by Pahala Basuki on Unsplash

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