There is an exciting, new laser technology that has enabled MBARI scientists to examine the structure of giant larvaceans. These are marine creatures that look like tadpoles and play a vital role in ocean ecosystems.
Recently, in a paper in Science Advances, MBARI researchers examined a technique to measure seawater flowing through giant larvaceans and related gelatinous animals. It gave a clue as to how much carbon dioxide oceans can absorb from the atmosphere. It was found that giant larvaceans help to move carbon from the upper layers of the ocean into the lower parts.
By building up balloon-like mucus structures called "houses," the larvaceans were able to concentrate food. They filtered tiny particles of food containing organic carbon from the surrounding seawater, according to Phys.org. The carbon was taken from the atmosphere.
The filters soon get overloaded with particles, after which the giant larvaceans discarded their houses. These houses carried the carbon and sank into the deep sea. The carbon was then consumed by animals or buried in the seafloor. Hence, the carbon was removed from the atmosphere for millions of years.
Because giant larvaceans were just centimeters in length but built houses that were a meter across, they were a challenge to study. Intact larvacean houses were nearly impossible to collect in a net or jar or to contain in a laboratory aquarium. Once they drifted into a solid net or wall, the houses fell apart.
MBARI Postdoctoral Fellow Kakani Katija has been studying giant larvaceans with particle image velocimetry (PIV), that have been used in laboratories for decades. With these measures, scientists could examine and measure complex water-flow patterns, including eddies, swirls, and currents.
In 2015, Katija used a "DeepPIV" system to study the giant larvaceans. Her system had a laser emitting a thin sheet of light and a video camera recording tiny particles in the water. They got lit up by the laser even as they passed through the light. Katija worked with MBARI engineers Alana Sherman, Dale Graves, and Chad Kecy. She mounted the laser and video camera on a remotely operated vehicle (ROV), MBARI's MiniROV.
Katija later joined Senior Scientist Bruce Robison and the rest of the DeepPIV team to employ their first field test on giant larvaceans. They used the MiniROV in order to reach 1,200 meters (4,000 feet) under Monterey Bay's surface.
When they switched on the laser, they suddenly found chambers and passageways that had never been seen before. "We were all shocked by how well it worked," said Katija. "There was a lot of oohing and aahing in the control room...As a result, we learned more about giant larvaceans during a single dive than we had in a previous couple of decades."
