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July 29, 2010 in Nation/World
Marine food chain’s lowest link declining
LOS ANGELES – The world’s phytoplankton appears to have been disappearing at a rate of about 1 percent a year for the past century, researchers announced Wednesday, a disturbing long-term trend for the microscopic algae that form the basis of the marine food chain and produce much of the world’s oxygen.
In reporting their findings in the journal Nature, the Canadian team said that since 1950 phytoplankton biomass has shrunk by about 40 percent. “A global decline of this magnitude? It’s quite shocking,” said Dalhousie University marine scientist Daniel Boyce, lead author on the study.
The new study combines historical records of ocean clarity with modern satellite data, the latter of which has only been available since the 1970s. Together, the modern and historical information provide an accurate long-term view of the state of phytoplankton.
The historical data was based on measurements of ocean clarity which involved lowering what looked like a white dinner plate into the ocean until observers lost sight of it. Water murkiness increases or decreases depending on the amount of phytoplankton or, more specifically, the plant’s green chlorophyll.
Thus, the scientists were able to convert historical data into specific measures of phytoplankton population, using it with the modern information to create a timeline of the algae over the past century.
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Teseract on July 29 at 3:28 p.m.
Question: If this article is correct, and the “world’s phytoplankton appears to have been disappearing at a rate of about 1 percent a year for the past century”, given that one century = 100 years, doesn’t that mean phytoplankton should be extinct, or very nearly so if the “about 1%” is slightly less than 1%?
monkeyman on July 29 at 9:25 p.m.
Answer to Teseract: They probably mean decline of 1% of the previous year every year, not of the original year.
After one year: 100 x 0.99
After two years: 100 x 0.99 x 0.99
etc…
This would mean after 100 years it will be:
100 x (0.99)^100 = 36.6
The calculation is very sensitive to the 0.99 figure, and it probably changes in a range every year to arrive at 60 (% of the original). I am actually getting 0.5% per year.
Teseract on July 30 at 1:45 p.m.
Thank you for the explanation, it’s amazing what a little math can do to clarify matters. Of course if the article had been phrased better perhaps it would have made more sense.