If you see a sailor or fisherman drop a white disk over the side of the boat, watch it sink for a while, then pull it back up, don’t worry. They haven’t spent too much time in the Sun — they’re doing science.
That’s the hope of Richard Kirby, a marine biologist at Plymouth University in England. He’s developed a smartphone app to help measure the amount of phytoplankton in the water.
These microscopic organisms sustain the entire marine food chain, and they produce about half of the oxygen in our air. A study released in 2010 said that global climate change had reduced the population of these creatures by as much as 40 percent. But many scientists disagreed, in part because it’s hard to measure just how much phytoplankton the oceans contain.
To correct that deficiency, Kirby and his collaborators created a project known as Secchi. It’s based on a device created a century-and-a-half ago by Pietro Angelo Secchi, a Vatican astronomer. It uses a white disk attached to a measuring tape. The disk is lowered into the water, and the user notes the depth at which the disk vanishes from sight. Waters that are rich in phytoplankton are cloudier, so the disk disappears faster.
Volunteers make a Secchi disk and use it to measure the water clarity anywhere in the world. They record their readings, and the app automatically transmits them to a central lab.
The project could give marine scientists a whole new way to assess the tiny plants that play a big role in the health of our entire planet.
