Here at Plankton Every Day, we are big fans of citizen science. “Go do some science!”, I like to say. There is a new, fantastic smartphone app called Secchi App that crowdsources phytoplankton measurements from all stripes of seafarers around the world. It was created at Plymouth University in the UK, and the app is free. To participate, you need a smartphone and a Secchi disc.
What is a secchi disc, you ask? It is a simple device that was invented in 1865 by Angelo Secchi, a Jesuit scientist and leader in astronomy, oceanography, meteorology and physics. It is still a standard tool in use today for determining the turbidity, or clarity, of any waterbody. Measuring turbidity is essentially a proxy for measuring plankton, silt or other suspended solids in water. Clear water = low turbidity, and cloudy water = high turbidity.
According to Richard Kirby, a Marine Institute Research Fellow at Plymouth University, a Secchi disk is “arguably one of the simplest marine sampling devices ever created.”
Here is Richard:
I will attest to the simplicity of this device. Similar to my very favorite scientific instrument, the Bucket on a Rope, a Secchi disc is simply a disc on a rope. It is weighted so that the disc can be dipped straight down in the water column, and the rope is marked for distance (or the rope itself is a measuring tape), so that you can measure “wet rope” aka “depth”.
You send the disc down until you can no longer see it. You bring it up until you can just barely see it again. Then you carefully lower it until it is just disappeared. Measure wet rope, log depth measurement into the app, and ping for GPS location.
I love this marriage of old analog tools and modern gadgets. Go do some science!