Summer is rapidly approaching, and with that comes the annual blooming of plants big and small. In the ocean, this means phytoplankton blooms. These microscopic floating plants are the basis of the marine food-chain, feeding everything from krill to whales.

This natural-colour satellite image is from the southern summer in January 2011, when Antarctica basks in 24 hours of sunlight. The Ross Sea is a shallow bay south of New Zealand on the Antarctic coast. Patches of open water surrounded by ice are exposed to constant sunlight, and nutrients are stirred up from deeper waters to feed massive booms that can stretch 100 to 200 kilometers long. While this is the largest annual bloom, the pale greens of phytoplankton make for beautiful imagery (and a welcome food supply) elsewhere in the world.

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At the opposite pole, this bloom in the northern summer of August 2011 at the Barents Sea once again captures the swirling beauty of drifting plants. The phytoplankton tints the water green to milky turquoise, reflecting the variation in species and concentration of plant life.

Not all blooms are an open buffet. Some species are toxic, blossoming into a plume of death for the region. While red tides of algae are the most famous form of marine-born death, massive rafts of cyanobacteria can smother a region just as effectively.

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Run-off from the mountains surrounding Lake Atitlán in Guatemala resulted in increased nutrients in the water. That fed a large bloom of cyanobacteria, the algae producing the bright green swirls in the deep blue lake in this November 2009 satellite photograph. These single-celled organisms are toxic to humans and other animals, but also create dead zones within the lake. They consume the available oxygen, suffocating other marine creatures. The bloom even kills itself, as only the top layer of the algae mats receive sunlight, leaving lower layers to die, decay, and release yet more toxins into the water.

Photography credit: NASA/Earth Observatory. Read more about the annual Ross Sea bloom, the seasonal change in phytoplankton species in the Barents Sea, or the toxic bloom in Guatemala.

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