The Ocean's Green Machines

Narration: Troy Cline


Seen from space, the blue Earth is unquestionably an ocean planet. Standing at the shore, the ocean looks endless...and empty. But below the surface, the ocean is actually brimming with miscroscopic plants called phytoplankton.

Mike Behrenfeld: "If you were to take an empty Coke can and go scoop up some water from the shore. In the Coke can you would have between, order of 75-100 million phytoplankton in that Coke can."

This invisible forest of phytoplankon is critical to life on Earth. Phytoplankton provide the base of the marine food web. They also help our planet breath. Through photosynthesis, phytoplankton generate one half of the oxygen produced on Earth that all animals, including humans, need to breathe. Like plants on land, phytoplankton need sunlight, water, and nutrients to grow. They thrive in surface waters where the sun's rays reach, and their nutrients come from many places. Cold waters carry essential nutrients from the ocean's lower depths to the hungry surface plants. The trillions of phytoplankton in the ocean are critical to study. But how do researchers track these invisible drifters? Ships move too slowly for a job this big. So researchers look at global distributions of phytoplankton from space. Over the past decade, scientists have deployed Earth observing satellites to remotely monitor the color of the oceans. By detecting ocean color from space, satellites monitor the abundance of phytoplankton in the water.

Mike Behrenfeld: "The reason that it's so important to study the phytoplankton from space is because it's the only way we can get a perspective of actually what's happening on the entire planet, over an entire year every day, in and out. And by doing this over many years, we can actually see how the Earth is changing. Changing from natural forcings, natural factors, as well as hopefully being able to detect changes that are due to human activities.

Phyoplankton respond rapidly to envionrmental changes. In the past decade, researchers have observed that global levels of phytoplankton tend to decrease as the ocean temperatures warm.

Gene Feldman: "During normal, physical mixing in the ocean, nutrients come up from the bottom. Phytoplankton are fertilized; they grow; the nutrients are depleted, the phytoplankton die or are eaten by something else. And the process just continues. Anything that happens that slows down that movement of cold, deep water to the surface would stop the flow of nutrients, which would cause the phytoplankton not to grow as well. And what's happened over the past ten years that we've been observing the oceans, in large areas of the ocean, they've warmed up. And what that means is the surface water has warmed, and it has essentially put a cap on that mixing process. As Earth's climate is changing, so is the ocean. Lowered levels of phytoplankton have implications for the marine food web. The increased CO2 in Earth's atmosphere impacts the ocean's chemistry. The seawater becomes acidic, which threatens marine life.

Mike Behrenfeld: "Every part of the Earth is inerconnected with the Earth as a system. The whole Earth system. The ocean influences the climate, the climate influences the ocean. Land influences the ocean; all of those pieces are interconnected."

It is more important than ever to track changes in the ocean from space, and new tools are helping researchers study the ocean and the phytoplankton that call it home. As Earth's climate continues to change, researchers will refine their tools and keep a close eyes on these powerful marine plants from space. Who knew that something so small could provide vital insight into the health of our home planet?