Humans are making oceans more acidic, NOAA warns. It could make red tide even worse

The world’s oceans are absorbing drastically higher amounts of carbon dioxide than in years past.

The phenomenon is a direct result of humans burning fossil fuels, according to the National Oceanic and Atmospheric Administration.

A new study by the organization shows that fossil fuels burned between 1994 and 2007 led to the absorption of 34 billion metric tons of carbon in the global ocean, or 2.6 billion metric tons per year.

That’s a four-fold increase compared to annual absorption rates between 1800 and 1994.

Pulling carbon dioxide from the atmosphere reduces atmospheric global warming, but the implications for the ocean are not good, the study found.

When dissolved into the ocean, the gas causes seawater to acidify. Acidification can prevent shellfish and corals from building healthy skeletons and negatively impact the health of fish and other marine life.

“The increasing load of carbon dioxide in the ocean interior is already having an impact on the shellfish industry, particularly along the U.S. West Coast,” said Richard Feely of NOAA’s Pacific Marine Environmental Laboratory in a news release. “We have been working with the industry to provide an early warning system against the most severe impacts of rising carbon dioxide levels.”

One life form that may not be negatively affected by acidification is Karenia Brevis— the algae that causes red tide blooms.

New research from Florida State University shows that the algae can thrive equally well in waters with low or high levels of carbon dioxide.

“Through our work we found that K. brevis is able to efficiently use available inorganic carbon for growth,” said graduate researcher Tristyn Lee Bercel in a story published by FSU News. “Even in bloom situations where it seems like CO2 could become limiting, the species is able to adjust and keep growing.”

At high levels, though, researchers found that the organism functions differently, using energy normally spent on carbon uptake to produce more brevotoxin.

The neurotoxin is responsible for the widespread fish kills that accompany red tide blooms.

It also accumulates in the tissues of tiny sea life like coquina clams, worms, mole crabs and insects, according to Audobon Florida.

From there, it travels up the food chain, sickening and potentially killing birds, sea turtles, dolphins and more.

The toxin can also impact sea life when breathed or ingested, according to the Florida Fish and Wildlife Conservation Commission.

In manatees, the toxin disrupts immune function by inhibiting one of the creature’s critical enzymes, NOAA says. Preliminary data from FWC lists 224 red-tide-related manatee deaths in 2018; Florida experienced a continuous, patchy bloom of the algae throughout the year.

Increased brevotoxin levels from CO2-fueled red tide would also be unpleasant for humans. At high concentrations, the toxin causes respiratory irritation, and it can accumulate to poisonous levels in the shellfish and seafood that people consume.

The FSU researchers’ findings related to brevotoxin were preliminary, and while not statistically significant, could illustrate how red tide will react to increased carbon dioxide levels.

“If there’s more carbon around, it could potentially alter cellular biochemical pathways in K. brevis,” Bercel said. “We only looked at the lower end of the projected CO2 and we saw a slight — although not statistically significant — increase in brevetoxin with enhanced CO2.”

Barcel and Sven Kranz, the other author of the study, speculate that increased carbon dioxide in Florida’s coastal waters could worsen the effects of red tide on coastal ecosystems.

More research on the species and its ecosystem are needed to confirm the theory, according to FSU News.

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Ryan Ballogg covers arts, entertainment, dining, breaking and local news for the Bradenton Herald. He won first place for feature writing in the Florida Press Club’s 2018 Excellence in Journalism Competition. Ryan is a Florida native and graduated from University of South Florida St. Petersburg.
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