Global phytoplankton decline over the past century

Phytoplankton are microscopic, free-floating plants that form the basis of the aquatic food chain. They also account for half of all photosynthetic activity, and thus produce much of the atmosphere’s oxygen.  Changes in the level of phytoplankton activity would have important implications on the health of the entire ecosystem, including human life.

Using a combination of historical and recent oceanographic data, a 2010 study published in Nature magazine, “Global phytoplankton Decline Over the Past Century,” calculates that the change in the level of phytoplankton activity over the last 100 years.

The study finds that:

• The annual global rate of decline of phytoplankton has been about 1% relative to the global median.
• Over the long term, in eight out of ten regions, rising sea surface temperatures were associated with declining phytoplankton. The negative relationship prevailed at low latitudes near the equator, where increased stratification has limited nutrient availability.
• At high latitudes, rising sea surface temperatures could affect positive phytoplankton growth, since the growth of phytoplankton could have been constrained by light availability and deep mixing.

The study’s findings are consistent with those on the effects of ocean warming on fishing and marine ecosystem. This further underscores the need for more sophisticated tools to support accurate measurement and forecasts of phytoplankton as well as the importance of reduce the causes and impact of climate change.

Tags: oceans, pollution, water