Ocean Acidification Could Alter Entire Ecosystems

According to new research from Stanford University scientists, hard-shelled species that are threatened by ocean acidification face other risks, too.  The researchers found that they are also threatened by other species that are not impaired by acidification.

“The oceans have absorbed 30 to 40 percent of the CO₂ that has been emitted into the atmosphere since the industrial revolution, and this causes very predictable changes in the ocean’s chemistry,” explained Kristy Kroeker, a biologist at Stanford’s Hopkins Marine Station.  ”It’s very straightforward chemistry that makes the water become more acidic.”

Pink coralline algae at Rose Atoll, located off the coast of American Samoa. Photo credit: NOAA.

Here’s the gist of ocean acidification:

• many hard-shelled organisms like clams, mussels, and corals, require carbonate ions to build their shells or skeletons
• when the ocean absorbs CO₂, it causes a reduction in carbonate ions
• as carbonate concentration decreases, so does the population of creatures that depend on it
• for more detail, follow this link to the NRDC

Most research involving ocean acidification involves only one species.  Kroeker’s goal was to observe how other species react to the chemical changes and to each other.

What she found was that in zones of high and low acidity, hard-shelled species like barnacles and pink coralline algae grow at similar rates.  Then, about halfway through this process, fleshy turf algae arrives and takes over because it thrives in highly-acidic conditions.

“Since our research suggests that ocean acidification favors fleshy seaweeds, management actions that protect the animals that eat fleshy seaweed (mainly fish and urchins) and limit the amount of local pollution could potentially slow the ecosystem changes,” Kroeker said.

To learn more:

• Read the full press release: Ocean acidification and interspecies competition could transform ecosystem, Stanford research shows
• Find the full paper in the journal Nature Climate Change: Ocean acidification causes ecosystem shifts via altered competitive interactions

Turf algae is a community of low lying species of marine algae. Photo credit: NOAA.

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