By Kathleen M. Wong

Think your garden is green? The blue waters of the oceans are actually much greener. Every year, microscopic marine plants called phytoplankton convert roughly 50 petagrams—50 trillion kilograms—of carbon dissolved in ocean surface waters into living tissue. That’s half of all the photosynthesis that occurs on the planet, and it happens at an astoundingly rapid pace.

"If I look out my window, I can see the same trees standing mostly unchanged year in and year out. The photosynthetic biomass on land is there for decades before being replaced. In the ocean, the extreme opposite occurs; the plants that are here one week have been eaten by the end of the week," says Jim Bishop, a Berkeley professor of earth and planetary science.

Bishop studies how plankton turnover contributes to the global carbon cycle. The amount of carbon these marine organisms take up, and how much gets entombed in the deep sea when they die, are key indicators of how earth is coping with global climate change. The process is critical to understanding and predicting present and future levels of atmospheric carbon dioxide. Yet the transitory nature of plankton, the size of the oceans, and often treacherous seas mean that plankton measurements from ships is spotty at best. "If I go to sea to study phytoplankton every three months, sixteen generations will have elapsed between the population I saw the first time and the one I saw later, and I have no idea how it evolved," Bishop says.

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