March 21, 2023 11:49 pm

Secchi disks are lowered into the water to measure phytoplankton abundance. Credit: AMT

A basic 19th-century tool is nonetheless helpful to ocean scientists in the age of satellites, new study shows. The study is published in the journal Frontiers in Marine Science.

A Secchi disk—historically referred to as a “dinner plate” by sailors—is utilised in the open ocean to measure concentrations of microscopic algae referred to as phytoplankton. Sailors reduce the white disk into the water and record the depth at which it disappears.

In the new study, a study group which includes the University of Exeter, Plymouth Marine Laboratory, Vrije Universiteit (Netherlands) and the Italian Institute of Marine Sciences (ISMAR) compared the efficiency of Secchi disks with satellites and higher-efficiency chromatography.

Secchi disks performed pretty much as nicely as contemporary techniques at monitoring phytoplankton abundance—meaning Secchi measurements going back additional than a century can assistance scientists fully grasp extended-term modifications in the ocean.

“Phytoplankton generate half the world’s oxygen and kind the base of ocean meals webs, so monitoring them aids us track anything from climate alter to the wellness of ecosystems,” mentioned Dr. Bob Brewin, from the Centre for Geography and Environmental Science on Exeter’s Penryn Campus in Cornwall.

“New technologies undoubtedly provides us new possibilities, but our study shows Secchi disks do a superior job of estimating chlorophyll (a way of measuring phytoplankton abundance)—which suggests we need to be in a position to integrate information from the previous with contemporary measurements. This provides us a priceless supply of extended-term information on how our oceans are altering.”

Secchi disks are nonetheless utilised all about the planet to monitor ocean biomass and water top quality, and co-author Dr. Jaime Pitarch, from ISMAR, mentioned the findings assistance their continued use. “It really is a basic, inexpensive tool, but our study shows it really is also remarkably productive,” he mentioned.

In reality, researchers which includes Dr. Brewin at Exeter, are operating on a project that will use 3D-printed Secchi disks to monitor water top quality in lakes in India and Africa, and coastal regions of the US.

Prior to the 1850s, mariners utilised a wide variety of objects (in the identical way as Secchi disks) to assistance with navigation, which includes cloths, pans and plates.

It was the Vatican astronomer Angelo Secchi, invited by the Papal Navy Commander Alessandro Cialdi to join a scientific cruise to study the murkiness of the sea in 1865, who standardized the technique.

The measurements in the new study have been collected on Atlantic Meridional Transect cruises.

Extra facts:
Robert J. W. Brewin et al, Evaluating historic and contemporary optical approaches for monitoring phytoplankton biomass in the Atlantic Ocean, Frontiers in Marine Science (2023). DOI: ten.3389/fmars.2023.1111416

Journal facts:
Frontiers in Marine Science