Oysters, like many bivalves, are important for marine ecosystems. The organisms filter water through their feathered gills, removing impurities as they inhale and exhale. In fact, native and invasive bivalves might filter the entire volume of the San Francisco Bay every 3-4 days!

However, oysters around the world are threatened by ocean acidification. The acidity breaks down the calcium carbonate shells of the oysters, as we reported in a video several months ago.

Recently, researchers discovered other effects of acidification on oysters and what the breakdown of the oysters’ calcium carbonate shells could mean for the acidic balance. Science Today sat down with the Academy’s own oyster expert, Dr. Peter Roopnarine, curator and chair of Invertebrate Zoology and Geology, to get some perspective on these recent studies.

In the first study, published earlier this month, scientists reported that acidification has negative effects for oysters in the larval stage. The acidity in the water makes the larvae expend much more energy than in neutral waters to make their shells.

“As the oyster larvae struggle early on and expend that embryonic energy,” Roopnarine says, “they have difficulty cranking up their own feeding.”

According to the paper’s lead author, George Waldbusser, “It becomes a death race of sorts. Can the oyster build its shell quickly enough to allow its feeding mechanisms to develop before it runs out of energy from the egg? They must build their first shell quickly on a limited amount of energy—and along with the shell comes the organ to capture external food more effectively.”

Last month, headlines reported that “Oyster Shells are an Antacid to the Oceans,” based on a study of oyster reefs in Chesapeake Bay. Roopnarine explains how oyster reefs are built over time, “Oysters do best on hard ground. The first oysters in a soft bottom environment eventually become the hard substrate that future oysters build upon. As the reef grows, the presence of the shells promotes a healthy, low acidic environment.” Or as the study’s introduction states, “Active and dense populations of filter-feeding bivalves couple production of organic-rich waste with precipitation of calcium carbonate minerals, creating conditions favorable for alkalinity regeneration.”

On a micro-scale, like the Chesapeake Bay, Roopnarine agrees that this could work. Restoration of oyster reefs could contribute to the reduction of ocean acidification problems. On a macro-scale, over geological time and large ocean mass, however, it seems that these oyster reefs could do little to undo the large amounts of CO₂ humans have been pumping into air (that’s absorbed by the oceans) for over a hundred years.

I asked Roopnarine about the San Francisco Bay’s oyster population. We had native oysters before overharvesting, pollution and sedimentation from gold mining in the Sierras buried the oyster reefs, Roopnarine says. A few are still found around the bay, but their numbers are small.

The oysters farmed locally are Japanese oysters, which, until a few years ago, were only found in hatcheries. Wild populations are now establishing themselves in the bay, Roopnarine says, which could be due to warmer temperatures. He and colleagues wrote a study a few years ago that looks at the Japanese oyster population locally.

With the important work these marine organisms do, it’s important we learn more about them to restore oyster reefs.

A former Academy staff-member, Jill Bible, is doing just this near Bodega Bay. To learn more watch this great video by the UC Communications team.

Image: Oysters showing the effects of ocean acidification, OSU

With the AGU meeting in town, it was a great week for science news! We covered several topics on Tuesday, Wednesday, and Thursday—and we’ll highlight a few more of them here for you.

Monday’s sessions included several discussions about the 2011 Tohoku tsunami in Japan—its effects on the local population and on far-reaching areas as well as how we can forecast future events.

One of the biggest surprises came during a presentation by Satoko Oki of the Earthquake Research Institute. She collected data from Japanese residents before and after the 2011 tsunami and found them less prepared for tsunamis after the Tohoku hit! When polled post 2011, they misidentified the minimum wave height from which to evacuate. They had correctly identified the minimum height less than a year before. The 80beats blog in Discover identifies the problem succinctly:

The Tohoku tsunami was so large–about 130 feet–that it may have dragged people’s expectations of what’s dangerous higher.

Another presentation revealed why the tsunami was so devastating—it was a “merging tsunami.” NASA researchers found that the tsunami doubled in intensity over rugged ocean ridges, amplifying its destructive power at landfall. This animation on NASA’s website illustrates the direction and power quite well.

The discovery helps explain how tsunamis can cross ocean basins to cause massive destruction at some locations while leaving others unscathed. The data raise hope that scientists may be able to improve tsunami forecasts.

Switching perspective from the oceans to outer space… NASA and NOAA held a joint workshop Tuesday on preparing for the solar max. As solar storms increase over the next 20 months or so, we can be prepared for what might and might not happen. This might remind you of a press briefing held earlier this year at the AAAS meeting that we covered here. It certainly reminded us how active the Sun can be, even during quiet times, as shown in this beautiful NASA video of SDO’s first year in space.

Finally, the Academy’s own Peter Roopnarine presented at the meeting on his research on oysters in the Gulf of Mexico. With colleagues, Peter has been testing for contaminants in the shells of oysters before and after the spill and hopes to model the spread of contaminants to other species through the food web. Check out this Science in Action video to learn more.

Image: Samuel Morse/US Air Force/Wikipedia

He and his colleagues found 400 year-old discarded oyster shells and other trash at the bottom of a long abandoned well in Jamestown, Virginia, site of the oldest English settlement in the US. The presence and geochemistry of the shells told the scientists that the water in the James River was much saltier at the time than it is now, confirming that the area was in the middle of a severe drought around the time the settlers arrived. The research was published yesterday in Proceedings of the National Academy of Sciences.

From Science News:

“It was interesting trying to figure out what was happening in the colony at a time when 70 to 80 percent of the colonists were dying,” Spero says.

Now, oysters independently confirm the tale from trees and historical accounts, comments William M. Kelso, an archaeologist at Preservation Virginia’s Jamestown Rediscovery project who was not involved in the study. “We’re getting a consistent story from science and the humanities,” he notes. “It’s pretty fantastic.”

(Several years ago, scientists used tree rings to posit that as the settlers arrived, the area was suffering its worse drought in 800 years.)

From Discover:

In an interesting twist, it was that increased salinity that extended the oysters’ range so far into the James River. So, the shells that the colonists discarded after they ate the oysters tell the tale of the drought that led the colonists to eat the oysters in the first place.

Besides serving as an indicator of the kind of water that may have been present in a particular region, oyster and clam shells, like tree rings, can also provide clues as to  the chemicals surrounding them at different stages of growth. In fact, the Academy’s Peter Roopnarine is currently involved with a project studying the effects of the Deepwater Horizon oil spill on oysters and clams in the Gulf of Mexico. This research effort involves studying shells now and then again at the end of the summer. You can read more about that study here.

Image credit: Preservation Virginia