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February 03, 2014 | By:  Alexis Rudd
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Marine Snow Days

Snow days are rare when you live in Hawaii, and so I was pretty excited for a snow day last week in DC. As I was watching the snow fall outside, it put me in mind of another kind of snow, which falls underwater. I first learned about the fascinating history of marine snow in 2006, when I was taking a class from Dr. Mary Silver at the University of California, Santa Cruz (UCSC). It turns out that Dr. Silver is writing up a history of the science of marine snow, and was happy to let me pick her brain on the subject.

Marine snow isn't made of water, like regular snow. Instead, it is made up of "detritus," which is a fancy word for gunk. This gunk is a slimy mix of dead organisms, diatoms, sand, dust, and the slimy houses of planktonic organisms called salps.

The name "marine snow" was first used in the logbooks of the Challenger expedition, in 1899, but the name wasn't popularized until William Beebe came along. William Beebe was a naturalist, scientist, and explorer. He is most famous for setting the 1934 record for deepest dive by a human by being lowered on a chain inside a giant steel sphere to a depth of 3028 feet. I don't know about you, but I would be mighty nervous about being three thousand feet underwater with nothing tethering me to the surface but a steel cable.

William Beebe is often called the Cousteau of his generation - he was not only a scientist, but he was also a naturalist who wrote for the public about the world he saw under the ocean. As a popularizer of science, he was often maligned by the scientists of his day for not being a "true scientist." Many popular scientists have faced similar criticism from fellow scientists, including Rachel Carson, who Beebe mentored early in her writing career. Although she is most famous for Silent Spring, her book about the effect of pesticides, Rachel Carson also wrote two beautiful books about the ocean. The Sea Around Us contains one of the most lyrical descriptions of marine snow:

With all this popular writing about marine snow, why wasn't there more science being done on it? Part of the problem was that, at the time, most oceanographers were focused on collecting samples from the ocean rather than observing what happened within it. They would go out on a boat, lower samplers into the sea, and then analyze the samples. For many years the water samplers that were most frequently used were emptied through a spigot on the side (kind of like the beverage dispensers that sometimes appear at summer barbeques). This meant that heavy material would settle to the bottom of the container, and wouldn't come out of the spigot when the scientist opened it to let the water out. To solve this problem, oceanographers would shake the bottle before emptying it to distribute the material that had sunk below the spigot evenly throughout the sample. Unfortunately, if you shake marine snow very hard in a bottle, it gets destroyed and doesn't look like marine snow anymore. The design of the bottle was making marine snow invisible to oceanographers.

Finally, some western scientists started noticing these particles (with the help of Japanese scientists, who had been looking at them from a submarine). In his 1982 biography, Gordon A. Riley describes being shown these particles of marine snow for the first time by a visiting scientist from Japan, Satoshi Nishizawa (italics are my own).

"Out on the boat, he showed me that there were visible particles, as collected in a transparent Van Dorn bottle, that were broken up merely by draining them out through the spigot. Although fragile, they were also biochemically sticky, so that small particles could aggregate into larger ones. The food value of such material was open to question, but there were bacteria and phytoplankton cells stuck to some of it, so that material formed in this way could be at least a food supplement for zooplankton. Satoshi was changing my viewpoint from the traditional one that the organic gunk is being gradually degraded from larger to smaller particles and eventually to the dissolved state, a useless dead end as far as the rest of the ecosystem was concerned until the inorganic nutrients were liberated. There could be reversals of possible ecological significance."

Although scientists were finally starting to realize that marine snow existed, their collection methods meant that they were still getting it wrong about where they came from. Gordon Riley, for example, thought that the organic particles or marine snow were formed by absorption on bubbles. He even used the word snow to describe his observations:

"Just for the hell of it, I bubbled the filtrate, and there was an immediate snowstorm of flakes."

Scientists finally got a good look at marine snow by simply jumping into the water and opening their eyes. Dr. William Hamner of the University of California, Los Angeles was one of the pioneers of blue water diving. At the time, scuba diving was infrequently used by oceanographers. Blue water diving allowed scientists to observe organisms in their natural environment, without disturbing or damaging them.

Dr. Mary Silver was just beginning her tenure as a professor at UCSC when two of her undergraduate students asked her to sponsor their blue water diving research project. After a couple of dives, they came back and complained that there was too much gunk in the water, and they couldn't see anything. She told them to try capturing the particles in the water, and she would help them identify them in the lab. The team found out that the nutrients on the snow were enriched many, many times. They had no funding for this project, but convinced a university administrator to give them $5000 for their project. This turned out to be a great investment, because, although many publishers told them that this research was unimportant, the students ended up with a publication in Science (something many well-established scientists only dream about). Dr. Silver and her two undergraduates had just published seminal research on how nutrients arrive in the deep sea.

I love this story, because it touches on one of my favorite aspects of science. I love that many exciting discoveries in science occur when people simply pay attention to something everyone else is ignoring. In the story of marine snow, early oceanographers pooh-poohed the work of "naturalists and popularizers" who looked at things, instead of blending them up and measuring them. But, as it turns out, the discovery of how nutrients move to the deep sea would never have happened without these "lookers." Not caring about whether looking at marine snow was cool or not allowed these scientists to discover something amazing. I love this story because it shows that anyone can do amazing, important science - even undergraduates looking at underwater goop!

For a more details about the history of Marine Snow, watch Dr. Mary Silver's talk here. Thank you to Dr. Silver for letting me interview her!

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