By Daniel Dunaief
Something is happening in the Twilight Zone of the ocean, but it’s unclear exactly who is involved and how fast the process is occurring.
Plants and animals are eating, living, defecating and dying above the so-called Twilight Zone and their bodies and waste are falling toward the bottom of the ocean. But most of that matter isn’t making it all the way to the ocean floor.
That’s where Gordon Taylor, a professor and director of the NAno-RAMAN Molecular Imaging Laboratory at the School of Marine & Atmospheric Sciences at Stony Brook University, comes in.
Taylor and Professor Alexander Bochdansky of Old Dominion University recently received a $434,000 three-year grant to study the way microorganisms eat, process and convert organic carbon — i.e., carbon that’s a part of living organisms like plants, sea birds and whales — into inorganic carbon, which includes carbon dioxide, carbonate, bicarbonate and carbonic acid.
“The inorganic carbon moves back and forth among these four chemical species,” Taylor explained in an email. Understanding the rate at which carbonic acid builds up can and will help lead to a greater awareness of ways the ocean, which used to have a pH around 8.2 — which is slightly basic, as opposed to levels below the neutral 7— is becoming more acidic.
They will start by deploying the traps at a single depth, about 985 feet, along the ocean off the coast of Virginia. “We are going to look at who the players are,” Bochdansky said. “There might be only a few key players that degrade this organic carbon. With [Taylor’s] great methods, we can measure the uptake rate in single microbes. This is really exciting.”
The Twilight Zone received its name because it is 650 to 3,300 feet below the surface of the water. Some faint light reaches the top of that zone, but most of that region, which includes creatures that use bioluminescence to attract or find prey, is pitch black.
“The directory of which inventories and fluxes decrease [is] still poorly understood,” Taylor said. “Animals eating the material is one mechanism and we don’t know how important that is compared to microbial decomposition or remineralization,” adding that the goal of this project is to “better define the role of microorganisms in returning carbon to the inorganic pool.”
Taylor is exploring this area with new tools that will allow a greater depth of understanding than previously possible. His group has developed new experimental approaches to apply Raman microspectrometry to this problem. The organisms they examine will include bacteria, fungi and protozoans.
Their experiment will explore which organisms are recycling organic carbon, how fast they are doing it and what factors control their activities. Through this approach, Taylor will be able to see these processes down to the level of a single cell as the instrument can identify organisms that have consumed the heavy isotope tracer.
The Raman microspectrometer uses an optical microscope with a laser and a Raman spectrometer. This tool will measure samples that are micrometers thick, which is smaller than the width of a human hair. The microspectrometer can obtain data from a 0.3-micrometer spot in a cell and he has even produced spectra from single viruses.
The scientists will place phytoplankton common to the region in incubators that Bochdansky developed. They will use a heavy carbon isotope, called carbon 13, that is easy to find through these experiments and see how rapidly microorganisms that colonize are incorporating the isotopically labeled carbon.
Taylor and Bochdansky received funding for the project through the Biological Oceanography Program at the National Science Foundation in the Directorate of Geosciences. Twice a year, the division makes open calls for proposals on any topic of interest to researchers. The scientists submit 15 pages of text that the NSF sends to peer reviewers. A panel meets to evaluate the reviews and ratings and decides which projects to fund.
Bochdansky and Taylor have been “acquainted for a long time and have shared similar interests,” Taylor said.
The carbon experiments in the Twilight Zone account for about a quarter of the work Taylor is doing in his lab. The other research also employs Raman microspectrometry. The United States only has one or two other facilities that do environmental research comparable to the one in Taylor’s lab at Stony Brook. Europe also has three such tools, which can look into single cells using lasers.
One of the other projects Taylor hopes to get funded involves studying the distribution of microplastics in the ocean. “The instrument I have is one of the best tools to look at microscopic plastic particles,” because it identifies the plastic polymer and its source, said Taylor, who is awaiting word on funding from the National Oceanic and Atmospheric Administration.
The other work involves exploring viruses that attack plankton.
“We are exploring Raman methods for early detection of viruses that attack plankton,” Taylor explained. Every organism in the ocean has at least one virus that has evolved to attack it.
As for his work on the Twilight Zone, Taylor said the area acts as a filter of sorts because less than 20 percent of the organic material entering at the top exits at the bottom.
Bochdansky added that these microbes are critical to processes that affect oceans and the planet.
“That’s something people often overlook,” Bochdansky said. “We can’t understand the ocean if we don’t understand it at the level or the scale that’s relevant to microbes.”
Bochdansky is thrilled to work with Taylor, who he’s known for years but will collaborate with for the first time on this project.
“In my lab, we have measured the turnover and release of carbon dioxide,” Bochdansky said. In Taylor’s lab, he measures “the actual feeding of microbial cells.”