Oysters To Serve As Biological Sensors In San Diego Estuaries
Monday, November 25, 2019
Photo by Erik Anderson
San Diego researchers will wade into a couple of local estuaries to deliver biological sentinels — oysters equipped with sensors that will monitor the bodies of water.
The scientists are looking for insight into a habitat that can undergo dramatic changes in a matter of hours.
Ten oysters were in a Scripps Institution of Oceanography lab last week being fitted for sensors by San Diego State University biologist Luke Miller and SDSU master’s student Gabriella Kalbach.
They attached magnets to the oyster shells. Long, thick wires connected the sensors to a yellow control box.
Kulback removed the slick coating on the shell of the wild-caught oysters so the glue that holds the sensors would have a chance to get a strong grip.
“You need to sort of, press it down, work it down onto the surface initially,” Miller said.
When the oyster opens its shell to breathe or feed, the magnets on each shell will separate. The sensors attached to the mollusks measure how much the shell opens and how frequently it happens.
“The kind of reading it’s giving there is measurement between this magnet and this sensor,” Kalbach said. “So, if I move this sensor around, we can see that the reading kind of changes.”
The small numbers on an LED display get larger when the shell opens and smaller when it is closed.
Being able to record how often the oyster opens its shell is valuable. Especially if researchers can compare the behavior to local water conditions.
They want to see how a biological creature reacts to the stress of living in an extreme environment.
Scripps Institution of Oceanography researcher Sarah Giddings said the oysters could help researchers understand how they cope.
“An estuary is a perfect environment to do this study because estuaries are where you have the meeting of the ocean,” said Sarah Giddings, a researcher at the Scripps Institution of Oceanography. “What that means is you have very strong gradients in temperature, salinity, all of the physical parameters that are much stronger than you see in the open ocean.”
Estuaries can lose access to saltwater. They can heat up. The water can be inundated with nutrients. And dissolved oxygen levels can crash in a matter of hours.
“And the key thing that we’re going to do is to make the link to the physical parameters, so the velocities, or the currents that they’re feeling, the salinity, the temperature and importantly the dissolved oxygen they’re experiencing,” Giddings said.
Right now, data recorded by the sensors are gathered by hand. Researchers actually go into the field to collect data chips from a small computer that floats above a rope and anchor holding the oysters.
If that information can be transmitted in real-time, scientists could record estuary conditions and oyster reactions as they happen.
“If we do see a direct response to their environment that we could actually use these sensors in the future to learn more about the environment,” Giddings said. “So actually use the oysters to tell us something about the environment and start to think about other organisms and other locations where we could deploy them.”
Researchers are releasing the oysters in the Los Peñasquitos Lagoon and the Tijuana River estuary.
The mollusks have zip ties glued onto their shells so they can be attached to a float or anchor. That gives scientists data from the surface and the estuary floor.
Oysters can thrive in that rapidly changing environments there, but they also struggle in extreme conditions.
“And so in those cases they will tend to just close themselves up completely, seal themselves off from the external environment and wait it out,” Miller said. “Basically wait a couple of hours. Every once in a while they will open a little bit, test and draw in a little water, to see what it tastes like in some sense. Whether there’s any oxygen in it.”
The oysters are photographed before they are released to see if they thrive this winter. Miller said he expects all of them to come back alive.
“We’ve taken these oysters from the original estuaries they grew up in,” Miller said. “We’re going to put them back in those same estuaries. And so, unless conditions get particularly bad during the winter and spring periods, especially if the oxygen drops particularly low. We expect that they’ll survive just fine.”
The oysters are being deployed in the Tijuana River estuary soon and they will be collected this spring.
When that happens, scientists will put together data sets that help them understand how living creatures are affected by changes in the local estuaries.
To view PDF documents, Download Acrobat Reader.