Underwater phytoplankton. Photo by Richard Kirby.
The latest recruits in the name of citizen science are going to be a raucous lot—well, at least according to stereotype. They’re all sailors, and armed with phones, measuring tape, and a circular white “Secchi” disk, they’re being tasked with an important project: mapping the impact of climate warming on the concentrations of phytoplankton in our seas.
Phytoplankton are tiny organisms that look something like delicate Christmas ornaments when viewed beneath a microscope. But they have an essential function, too: They form the base of the marine food chain, supporting vast populations of sea creatures and allowing them to develop and thrive. They also account for 50 percent of photosynthesis on Earth, and play a key role in the planet’s carbon cycle.
Phytoplankton tend to inhabit the layers of ocean closer to the surface, so they’re increasingly pressured by climate change and associated ocean warming. Richard Kirby, a plankton biologist at the United Kingdom’s Plymouth University Marine Institute, is leading the project, and as he explained in a press release:
Like all marine creatures, phytoplankton have a preferred optimum sea temperature no matter where they are in the world and therefore they will either move to different areas or decrease in number if the sea temperature changes.
Research published a few years ago in Nature showed that over the last century, phytoplankton numbers have declined by almost 50 percent on account of climate change. But these findings were considered to be contentious, largely because little actual field sampling took place to back it up. So to fill that gap, the project leaders have designed their citizen science effort to find out more: are the microorganisms experiencing a decline? And if so, where? As Kirby said, “We need to know more about how the phytoplankton are changing in order to understand the effects on the ocean's biology. Phytoplankton underpins the marine food chain, without it the seas would be a barren wilderness."
A Secchi disk underwater. Photo by Richard Kirby
Today, the researchers release a smartphone app called Secchi which, coupled with measuring instruments, can be used to record information about phytoplankton that will then be stored and made accessible in an online database.
This is where the odd collection of instruments comes in. First there is the Secchi disk—the device named after Father Pietro Angelo Secchi, a 19th century astronomer who invented it to measure the cloudiness of the water in Mediterranean seas. The flat, white disk is thirty centimeters in diameter, weighted at the bottom end, and attached to a length of measuring tape at the top. The idea is that citizen scientists—made up of sailors and fishermen—dip the disk into the ocean whenever they have the chance, and record the depth at which the it disappears from sight. The faster it disappears, the more phytoplankton are present. The sailors (who each have a unique Secchi user id) record the depth at which they can no longer see the disk on the Secchi smartphone app.
Along with location and temperature measurements, the depth recordings are gathered through the app, and will ultimately be channeled into a free online archive of information about the distribution and population densities of ocean phytoplankton—possibly highlighting areas of concern. “Over time, the interactive data set will be linked with satellite remote sensing data of ocean color to create a resource for both the general public and scientists alike,” the Secchi App press release read.
Kirby emphasized that citizen scientists are in high demand: “The Secchi Disks are still used by marine scientists to study phytoplankton, but there are too few scientists to survey the world’s oceans as well as we would wish.”
The researchers hope that the project turns global, with seafarers from all parts of the world becoming involved over the next few years. That way, they can build up a database that covers a large area, and that grows over time—possibly making theirs the largest plankton-monitoring project in the world, and generating keen insights into the ocean’s underworlds.
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