Marine Phytoplankton in decline over the last century


Using the Secchi disk ca. 1910

Research collected for more than a century is helping Dalhousie University researcher Daniel Boyce in his quest to examine the health of the world’s oceans.

A simple tool known as a Secchi disk as been used by scientists since 1899 to determine the transparency of the world’s oceans. The Secchi disk is a round disk, about the size of a dinner plate, marked with a black and white alternating pattern. It’s attached to a long string of rope which researchers slowly lower into the water. The depth at which the pattern is no longer visible is recorded and scientists use the data to determine the amount of algae present in the water.

More specifically, the research is focused on a particular type of algae known as phytoplankton. This is the first time that significant research has been complied and examined to study the algae levels in the world’s oceans.

Phytoplankton provides food for basically everything in the ecosystem, from fish right up to human beings,” says Mr. Boyce, a PhD candidate with the Department of Biology at Dalhousie. “Phytoplankton is also important in maintaining sustainable fisheries operations and the overall health of the ocean. We need to make sure that the numbers do not continue to decline.”

The researchers found that the number of phytoplankton has been decreasing by a rate of about one per cent per year, for the past 110 years. While this might not seem like a large number, this translates into a decline of about 40 per cent since 1950. In total, just under half a million observations were compiled to be able to estimate phytoplankton levels through the years…

Based on the research collected, phytoplankton levels have decreased in eight out of 10 ocean regions.

Boyce makes the point that we don’t thoroughly understand all the ramifications of such a decline. Wanna bet it doesn’t bode well for our continued existence?

It’s like running out of dirt.