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NASA Articles » Marine Phytoplankton Blooms
Satellite Images of Marine Phytoplankton Blooms
A collection of NASA images from worldwide oceans. Commentary by NASA.
Phytoplankton are microscopic plants that grow in the sunlit surface waters of the ocean. When enough phytoplankton grow in one place, the bloom can be seen from space.
Phytoplankton play a large role in sustaining ocean ecosystems and global climate. The plants are the base of the marine food chain. Places where blooms are frequent often support a thriving marine population. Since the plants need nutrients like iron to grow, fertile waters are often near a continental shelf in areas where cool water from the ocean's depths pushes to the surface. This upwelling water carries with it nutrients that had settled to the ocean floor; the nutrients allow the water to sustain large phytoplankton blooms.
Phytoplankton influence global climate by regulating gases in the atmosphere. Like all plants, phytoplankton absorb carbon dioxide and release oxygen as they grow. When the plants die, they sink to the ocean floor, carrying the absorbed carbon with them. Over the course of the Earth's history, the oceans have become the primary sink for atmospheric carbon dioxide. Since carbon dioxide is a greenhouse gas (it traps heat at the Earth's surface), the Earth would be a much warmer place without phytoplankton.
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Phytoplankton Near Elephant Island - Antarctica: The Antarctic Peninsula stretches north from the northwest side of the continent
towards the southern tip of South America. Scattered islands punctuate the Atlantic beyond the northernmost tip of the peninsula,
and among these is Elephant Island. The white outline of the island resembles the head of an elephant with its trunk extended.
White flecks of ice float in the ocean around the island. The ocean itself is literally alive with color. The wide blue swirls
are formed by microscopic plants, phytoplankton, that grow near the surface of the water. Their outer scales are made of calcium
carbonate, a white substance that reflects light back to the satellite. When viewed through the ocean water, the phytoplankton
often look blue, as they do here. The water immediately around the island is tan and green, probably from sediment washing from
the island. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this image on
September 13, 2003. (A MODIS image from NASA's Aqua satellite prepared by Jacques Descloitres.)
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Phytoplankton Bloom off Namibia: A flash of blue and green lit the waters off Namibia in early November 2007 as a phytoplankton bloom grew and faded in the Atlantic Ocean. The bloom stretches from north to south along hundreds of miles, although it is brightest in the center of this image. Such blooms are common in the coastal waters off southwest Africa where cold, nutrient-rich currents sweep north from Antarctica and interact with the coastal shelf. At the same time, the easterly trade winds push surface water away from the shore, allowing water from the ocean's floor to rise to the surface, bringing with it iron and other material. The suffusion of nutrients from both the currents and upwelling water creates an environment where tiny surface-dwelling ocean plants thrive.
Phytoplankton blooms are so abundant off Namibia that their death and decomposition often robs the water of dissolved oxygen. As the plants die, they sink to the ocean floor where bacteria consume them. There is so much plant material that the bacteria use all of the oxygen available in the water before they finish breaking down the plants, creating a dead-zone in the water where fish can't survive. Anaerobic bacteria, which don't require oxygen, take over in the decomposition process, releasing sulfur dioxide as a byproduct. The sulfur dioxide interacts with the ocean water to create solid sulfur and hydrogen sulfide, a poisonous gas, which eventually erupts to the surface,
sometimes killing fish. Though no eruption is readily apparent in this image,
hydrogen sulfide eruptions are often visible in satellite imagery because the solid sulfur colors the water a milky
yellow-green. (A MODIS image from NASA's Aqua satellite. Commentary by NASA.) |
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Algal Bloom in the Barents Sea: A break in the clouds provided a window to a brilliant display of color in the Barents Sea north off Norway on August 1, 2007. The bright aquamarine hues suggest that this is likely a coccolithophore bloom. A coccolithophore is a tiny, surface-dwelling ocean plant that is coated with microscopic limestone (calcite) scales. This white coating makes the plant highly reflective. It reflects nearly all of the light that hits it, and it is this reflected light that gives the ocean the radiant blue color seen in this image.
Coccolithophores flourish in nutrient-poor, sub-polar waters. Like other types of microscopic ocean plants (phytoplankton), coccolithophores are an important food source for fish and other marine animals. Coccolithophore blooms occur when large numbers of the plants grow in one place. Such blooms can be large: The visible portion of this bloom covers about 150,000 square kilometers (57,000 square miles) or roughly the area of Wisconsin. (A MODIS image from NASA's Terra satellite. Commentary by NASA.) |
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Phytoplankton Blooms in the Black Sea: The Black Sea more closely resembled mixed paint on an artist's palette than the normally black surface of deep water in this image captured this image on June 20, 2006. Swirls of color ranging from deep olive green to bright turquoise were created by a massive phytoplankton bloom that covered the entire surface of the sea. The sea was able to support such a large bloom largely because of its unique structure.
In the spring of 2006, floods on the Danube River swept over broad stretches of farmland. The floods likely washed sediment, fertilizers, and animal waste into the Danube and the Black Sea. The extra iron, phosphates, and nitrates in the flood debris may be supporting the extensive bloom seen here. Such blooms can be both beneficial, because they provide food for fish, and dangerous, because decaying plant matter saps oxygen out of the water. If enough phytoplankton from a large bloom die and decay, the water may become so oxygen poor that fish can no longer survive in it. The result is a dead zone where little can survive.
Dead zones normally happen near the mouths of large rivers where fertilizers and agricultural waste are concentrated in the ocean. The Black Sea is one of the world's largest dead zones, though its dead zone is related to its stratification as much as to fertilizer run-off. When plants and other organic matter sink to the floor of the sea, they decay in the salty layer of water. Since the denser salt water does not mix with the fresher water at the surface, there is no way to replenish the oxygen used during the decay process. As a result, the lower layer of the Black Sea is totally oxygen-free. (A MODIS image from NASA's Aqua satellite. Commentary by NASA. |
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Phytoplankton surround the Falkland Islands: Millions of tiny, single-celled plant-like organisms ring the Falkland Islands in this photo-like image taken on January 13, 2008. These organisms, called phytoplankton, reflect light, coloring the ocean with whimsical swirls of blue and green. The bloom traces the course of the Malvinas (Falkland) Current, which sweeps north around the Falkland Islands and along the east coast of South America. A branch of the Antarctic Circumpolar Current, the strong current is cold and laden with nutrients. Because the current brings nutrients into the sunlit surface waters where plants can grow, the Malvinas Current often feeds large blooms such as this one.
Phytoplankton are the base of the marine food chain, so regions in which phytoplankton flourish tend to host a wide diversity of life. The tiny plants also play a large role in the global carbon cycle. Like larger plants, phytoplankton absorb carbon dioxide from the atmosphere and turn it into carbohydrates during photosynthesis. When the phytoplankton (or the animals that eat them) die, some of their remains sink to the ocean floor, transporting the carbon to the bottom of the ocean. (A MODIS image from NASA's Terra satellite. Commentary by NASA.)
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North Atlantic Algal Bloom: Reminiscent of the distinctive swirls in a Van Gogh painting, millions of microscopic plants color the waters of the North Atlantic with strokes of blue, turquoise, green, and brown. Fed by nutrients that have built up during the winter and the long, sunlit days of late spring and early summer, the cool waters of the North Atlantic come alive every year with a vivid display of color. The microscopic plants, called phytoplankton, that give the water this color are the base of the marine food chain.
Some species of phytoplankton are coated with scales of calcium (chalk), which turn the water electric blue. Chlorophyll and other light-capturing pigments in others give the water a deep green hue. The proliferation of many different species in various stages of growth and decay provides many nuances of color in this concentrated bloom.
The bloom stretches across hundreds of kilometers, well beyond the edges of this photo-like image, captured on June 23, 2007. The upper left edge of the image is bounded by Greenland. Iceland is in the upper right. Plumes of dust are blowing off the island, probably adding nutrients to the surface waters to its south. (A MODIS image from NASA's Aqua satellite. Commentary by NASA.)
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Phytoplankton Bloom Off Ireland: Swirling clouds of blue and green lit the Atlantic Ocean west of Ireland on June 2, 2006. (A MODIS image from NASA's Aqua satellite. Commentary by NASA.)
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