Climate Number: 0.006 milligrams per cubic meter per year
Oceanic phytoplankton – microscopic organisms that use the sun’s energy to convert carbon and water into the sugars that make up their bodies – account for about half of the production of organic, or living, matter on Earth. These phytoplankton feed the zooplankton, which eventually feed the larger fishes that feed seabirds, marine mammals and humans. In short, all life in the oceans is fueled by phytoplankton. Also, because phytoplankton do account for so much of Earth’s living matter, they play a key role in carbon uptake and thus the composition of the atmosphere, affecting land-based life in the process. The rise in global sea surface temperatures over the last century has resulted in more stratified oceans. Strongly stratified oceans have warm and nutrient poor surface layers, with less cool and nutrient rich water delivered to surfaces from the depths. The phytoplankton, which grow near the surface where sunlight is available, now have fewer nutrients to work with than they did in the early 20th century when temperatures were cooler. How many phytoplankton there are in the water is measured by chlorophyll concentrations. Chlorophyll is the chemical that enables the phytoplankton to harness the sun’s energy for life. On average, each cubic meter of seawater contains 0.56 milligrams of chlorophyll. This concentration is declining at a rate of 0.006 milligrams per cubic meter per year.
For Comparison: The amount of chlorophyll in one cubic meter of sea water, 0.56 milligrams, is about the same mass as 10 grains of salt.
Seasons: Winter, Spring, Summer, Fall
Sources: Boyce, DG et al. “Global phytoplankton decline over teh past century.” Nature 466(2010): 591-596 and Science Daily “Marine Phytoplankton Declining: Striking Global Changes at the Base of the Marine Food Web Linked to Rising Ocean Temperatures.” 28 July 2010. Accessed Online 31 July 2010 <http://www.sciencedaily.com/releases/2010/07/100728131705.htm>
