Acidic waters may take a toll on marine plants

Warmer, acidic waters may take a toll on California's coral-like algae, making it harder for young abalone to "settle down."

Jennifer Smith and her graduate students have, in laboratory experiments, observed slower growth rates among hard, crusty "calcifying" algae exposed to warmer, more acidic conditions.

They have also observed faster growth in soft, fleshy brown and red seaweeds, common along the California coast.

California Sea Grant is currently funding Smith, a professor at Scripps Institution of Oceanography, UC San Diego, to study how single species of algae and whole communities of benthic organisms may respond to climate change scenarios predicted for 2100.

Her co-investigators on the project are professors Scott Hamilton and Michael Graham, both at Moss Landing Marine Laboratories.

The research teams have recently deployed collecting trays off Carmel and La Jolla to gather natural assemblages of bottom species (see image below). These trays will later be transported to the Smith lab and placed in tanks pumped with extra carbon dioxide (CO2), which makes the water more acidic.

Some of the settlement tiles will be exposed to current ocean water temperatures and some will be exposed to conditions  3 to 4 degrees Celsius warmer than current conditions, Hamilton explained.

The idea is to see how species compete and who will ultimately "win" and "lose" when the seawater-chemistry game is changed.

Of course, people could be the biggest losers. Most of the oxygen we breathe (about 70 percent) is made by marine plants. The ocean is also a sponge for our CO2.

At present, about 40 percent of the CO2 that we emit by burning fossil fuels is absorbed by the ocean. Some scientists think that the ocean's ability to mop up after us will slow down in the future. Humans have a lot of skin in the game, in terms of ocean health.

In the last part of the Sea Grant project, the researchers will look at whether climate change may interfere with how algae and red abalone communicate via chemical cues (that nobody really understands yet).  What scientists do know is that abalone larvae preferentially descend and settle down on coralline algae. It's their preferred habitat in their transition from free-swimming larvae to miniature versions of  their adult selves. The scientists hypothesize that weaker, more fragile coralline algae may not emit the same chemical cues to young abalone.

Written by Christina S. Johnson