"The future of nutrition is found in the ocean." Jacques Cousteau
When plankton are bothered, or stressed by UV light, their chemistry takes over.
The plankton try to protect themselves by producing a chemical compound called DMSP, which some scientists believe helps strengthen the plankton's cell walls. This chemical gets broken down in the water by bacteria, and changes into another substance called DMS.
DMS then filters from the ocean into the air, where it breaks down again to form tiny dust-like particles. These tiny particles are just the right size for water to condense on, which is the beginning of how clouds are formed. So, indirectly, plankton help create more clouds, and more clouds mean that less direct light reaches the ocean surface. This relieves the stress put on plankton by the Sun's harmful UV rays.
Source: http://www.nasa.gov/vision/earth/environment/0702_planktoncloud.html
| Researchers found surprising evidence of sea salt and frozen plankton in high, cold, cirrus clouds, the remnants of Hurricane Nora, over the U.S. plains states. Although the 1997 hurricane was a strong eastern Pacific storm, her high ice-crystal clouds extended many miles inland, carrying ocean phenomena deep into the U.S. heartland. Kenneth Sassen of the University of Utah, Salt Lake City, and University of Alaska Fairbanks; W. Patrick Arnott of the Desert Research Institute (DRI) in Reno, Nev.; and David O. Starr of NASA's Goddard Space Flight Center, Greenbelt, Md., co-authored a paper about Hurricane Nora's far-reaching effects. The paper was published in the April 1, 2003, issue of the American Meteorological Society's Journal of Atmospheric Sciences. Scientists were surprised to find what appeared to be frozen plankton in some cirrus crystals collected by research aircraft over Oklahoma, far from the Pacific Ocean. This was the first time examples of microscopic marine life, like plankton, were seen as "nuclei" of ice crystals in the cirrus clouds of a hurricane. |
| This image captures a plankton bloom in the Capricorn Channel off the Queensland coast of Australia. The whispy pattern of the bloom suggests that the plankton are Trichodesmium-a photosynthetic cyanobacteria, also called "sea saw dust" that is common in the world's oceans. Trichodesmium is frequently observed around Australia this time of year. In fact, Captain Cook's ship logs written while he was sailing in Australian waters in the 1700s contain detailed descriptions of Trichodesmium blooms. Trichodesmium species are particularly important because of their role as primary producers: by sheer abundance, they fix a large amount of CO2 and N2. |
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| Astronauts frequently photograph large plankton blooms during their missions because a significant portion of the ISS orbits cross long stretches of ocean. In the process, astronauts become acute observers of subtle changes in sea surface dynamics. Imagery of surface plankton blooms are multi-dimensional (in space and time) visualizations for the unique physical and chemical circumstances that support the blooms. Astronauts are trained and encouraged to document phytoplankton blooms, and to make repeated observations to better understand the longevity and temporal variations of the blooms. |
David Siegel, professor of geography at the University of California, Santa Barbara, and director of the Institute for Computational Earth System Science, made the discovery with his former Ph.D. student Dierdre Toole, who is now based at Woods Hole Oceanographic Institute.
In an article in the May 6 issue of the journal Geophysical Research Letters, the scientists explain their research in the Sargasso Sea, approximately 50 miles southeast of the island of Bermuda. Siegel's research group has been making observations at this location since 1992.
Phytoplankton are tiny, single-celled floating plants. They inhabit the upper layers of any natural body of water where there is enough light to support photosynthetic growth. They are the base of the oceanÕs food web, and their production helps to regulate the global carbon cycle. They also contribute to the global cycling of many other compounds with climate implications.
One of these compounds is a volatile organic sulfur gas called dimethyl sulfide or DMS. Scientists had previously theorized that DMS is part of a climate feedback mechanism, but until now there had been no observational evidence illustrating how reduced sunlight actually leads to the decreased ocean production of DMS. This is the breakthrough in Toole and Siegel's research. They describe how the cycle begins when the ocean gives off DMS to the lower atmosphere. In the air, DMS breaks down into a variety of sulfur compounds that act as cloud-condensing nuclei, leading to increased cloudiness. With more clouds, less sunlight reaches the Earth and the biological processes which produce DMS are reduced.
According to their research, it appears that phytoplankton produce organic sulfur compounds as a chemical defense from the damaging effects of ultraviolet radiation and other environmental stresses, in much the same way as our bodies use vitamins E and C to flush out molecules that cause cellular damage.
Siegel and Toole found that ultraviolet radiation explained almost 90 percent of the variability in the biological production of DMS. They showed that summertime DMS production is "enormous," and that the entire upper layer of DMS content is replaced in just a few days. This demonstrates a tight link between DMS and solar fluxes.
"The significance of this work is that it provides, for the first time, observational evidence showing that the DMS-anti-oxidant mechanism closes the DMS-climate feedback loop," said Siegel. "The implications are huge. Now we know that phytoplankton respond dramatically to UV radiation stresses, and that this response is incredibly rapid, literally just days."
A green ocean is a productive ocean; the light from the sun fuels the "bloom" of phytoplankton, tiny ocean plants that turn the sea's surface a light green each spring. This production in turn drives ocean food webs. New research, published in the journal Science on April 26, assesses the color of the ocean and finds that it may yield clues about the relation between marine ecosystems and the climate system. The research was funded by the National Science Foundation (NSF).
David Siegel, a scientist at the University of California, Santa Barbara, and colleagues analyzed ocean color data from the satellite Sea-viewing Wide Field of view Sensor (called "Sea WiFS") to address the factors regulating the spring bloom of phytoplankton in the north Atlantic Ocean. "The productivity of the ocean [from blooms] is well established," said Siegel. "What we don't know is how it gets recycled. We're trying to get at how the ocean's biological pump works." The biological pump is the mechanism by which carbon dioxide is exported from the surface ocean into the deep ocean via sinking particles, like the remains of phytoplankton as they die off after blooms. It is a critical factor in understanding global climate change.
From the satellite is information Siegel and colleagues were able to deduce the conditions required to start a spring bloom: appropriate amounts of light reaching down into the water column, a condition that occurs when ocean waters "turn over" or mix, in spring.
"When viewed from space, the north Atlantic spring bloom is among the largest mass greenings observed on the Earth's surface," said Siegel. The blooming progresses at speeds of 20 kilometers per day, leaving a green wake in its path.
Jim Yoder, a co-author of the paper, on leave from the University of Rhode Island Graduate School of Oceanography and currently division director of ocean sciences at the National Science Foundation said, "We used satellite and other data to observe the start of the phytoplankton growth period in the north Atlantic Ocean, and we were able to explain the timing of the spring growth period in the entire north Atlantic."
Previous research on spring blooms was done at sea with microscopes and other tools. But by using satellites, Siegel and Yoder were able to evaluate the process using tens of thousands of data points, rather than just a few.
One advantage provided by satellite ocean color data is measurements that cover the entire north Atlantic during all seasons and years. Such measurements, if correctly interpreted, are a tool for studying natural phytoplankton variability - an important characteristic of marine ecosystems. The results of the present study illustrate an approach for using satellite measurements to study the year-to-year ecosystem variability associated with changes to the climate system and to the location and strength of ocean currents.
Source: http://earthobservatory.nasa.gov///Newsroom/MediaAlerts/2002/200204258802.html
For more studies go to: http://phytoplankton.gsfc.nasa.gov/
http://www.mos.org/oceans/life/webs.html
http://en.wikipedia.org/wiki/Diatom