To estimate how much carbon these sinkers might be delivering to the seafloor, Robison first needed to find out how common they were. For ten years (from 1994-2003), he and his research team had been conducting monthly surveys of midwater organisms at ten different depths in Monterey Bay using MBARI's ROV Ventana. As part of their study of sinkers, the scientists pored over hundreds of hours of video taken during these surveys, counting both inhabited larvacean houses and sinkers themselves.
Knowing the volume of water that was observed during each midwater survey, Robison and coauthors Rob Sherlock and Kim Reisenbichler were able to estimate the overall abundance of sinkers in Monterey Bay. Over the ten-year period, they observed an average of about four sinkers per day for every square meter of deep seafloor. In other words, a patch of seafloor the size of a large dinner plate might receive carbon from about 100 sinkers over a year's time.
To complete their study, the scientists also needed to know how much carbon each sinker transported to the seafloor. But first they had to collect some sinkers. Since the sinkers could not be collected individually using sediment traps, the team relied on MBARI's skilled ROV pilots to do the job. Catching bits of drifting mucus using a three-ton underwater robot was no easy feat. As Robison put it, "We collected more than a hundred of these things, and every one of them was a major challenge. About one in four attempts was successful. The patience and skill of those pilots was just amazing."
Back in the lab, the researchers carefully measured the amount of organic carbon in each sinker. Finally, by multiplying the number of sinkers reaching t
Source:Monterey Bay Aquarium Research Institute