PHYTOPLANKTON – Secchi Disk
The marine phytoplankton account for approximately 50% of all photosynthesis on Earth and, through the plankton food web that they support, they both underpin the marine food chain and play a central role in the global carbon cycle strongly influencing the Earth’s climate. Living at the surface of the sea the phytoplankton are particularly sensitive to changes in sea surface temperature. A recent study of global phytoplankton abundance over the last century concluded that global phytoplankton concentrations have declined due to rising sea surface temperatures as a consequence of current climate change. To give some brief background about the project: Two years ago a group of Canadian marine scientists reported that the phytoplankton in the oceans had declined globally by 40% since the 1950s due to climate change. Their study provoked controversy among marine scientists however, as some thought they saw contrary results. Part of the controversy stems from a lack of data about the marine phytoplankton due to the fact that the oceans are vast and there aren’t that many scientists to cover them. Because of the important role played by the phytoplankton in underpinning the whole marine food chain, we need to know if, how and why they are changing, and this is where we believe citizen science can help. We need to know much more about these changes and you can help by making a simple piece of scientific equipment called a Secchi Disk and using the Secchi App. The project’s aim is to ask sailors to help create the biggest global study of the marine plankton, starting now and carrying on forever. I am writing to ask if you would like to participate, perhaps also mention the project on your blog, and tell other voyagers you meet in order to help us raise awareness. The Secchi disk, created in 1865 by Pietro Angelo Secchi SJ, is a circular disk used to measure water-transparency in oceans and lakes. The disc is mounted on a line, and lowered slowly down in the water. The depth at which the disk is no longer visible is taken as a measure of the transparency of the water. This measure is known as the Secchi depth and is related to water turbidity.