Climate Change is Killing the Oceans' Microscopic 'Lungs'
Global warming has begun to change the way microscopic plant life in the oceans absorbs carbon dioxide from the atmosphere - a trend that could lead to a dramatic increase in the heating power of the greenhouse effect.
Satellite data gathered over the past 10 years has shown for the first time that the growth of marine phytoplankton - the basis of the entire ocean food chain - is being adversely affected by rising sea temperatures.
Scientists have found that as the oceans become warmer, they are less able to support the phytoplankton that have been an important influence on moderating climate change.
The fear is that as sea temperatures continue to rise as a result of global warming, the loss of phytoplankton will lead to a positive-feedback cycle, where increases in carbon dioxide concentrations in the atmosphere leads to warmer oceans, and warmer oceans lead to increasing carbon dioxide concentrations.
"Rising levels of carbon dioxide in the atmosphere are a key part of global warming. This study shows that as the climate warms, phytoplankton production goes down, but this also means that carbon dioxide uptake by the ocean plants will decrease," Professor Behrenfeld said. "That would allow carbon dioxide to accumulate more rapidly in the atmosphere, making the problem worse."
Despite their small size, phytoplankton account for about half of the photosynthesis carried out by all plants on Earth. And phytoplankton have a high turnover because they are quickly eaten by small marine animals - making them even more vulnerable to climate change.
"This fast turnover and the fact that phytoplankton are limited to a thin veneer of the ocean surface, where there is enough sunlight to sustain photosynthesis, makes them very responsive to climate change," Professor Behrenfeld said. "This was why we could relate productivity changes to climate variability in only a 10-year record. Such connections would be much harder to detect from space for terrestrial plant biomass."