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Nitrogen fixation and phytoplankton blooms in the southwest Indian Ocean
August 17, 2009Nitrogen fixation and phytoplankton blooms
Observations made by Southampton scientists help understand the massive blooms of microscopic marine algae - phytoplankton - in the seas around Madagascar and its effect on the biogeochemistry of the southwest Indian Ocean.
The observations were made by researchers based at the National Oceanography Centre, Southampton (NOCS) during a 2005 hydrographic survey south and east of Madagascar while aboard the royal research ship RRS Discovery. The fully analysed results are published in the journal Geophysical Research Letters.
Nitrogen-fixing bacteria convert atmospheric nitrogen into nitrogen compounds that organisms can then use as food. This process is thought to be important in areas of the ocean where nitrogen-based nutrients are otherwise in short supply, and the researchers confirm that this is indeed the case in the region south of Madagascar.
But there were some surprises. Previously, it has been thought that the large-scale autumn bloom that develops in this region is driven by nitrogen-fixing blue-green algae, or cyanobacteria, called Trichodesmium, colonies of which the researchers found to be abundant. However, the 2005 bloom was dominated by a diatom - a type of phytoplankton - the cells of which play host to another nitrogen-fixing cyanobacterium called Richella intracellularis, with Trichodesmium apparently playing second fiddle.
Diatoms have relatively large cells, and when they die they sink down the water column, carrying with them carbon that is ultimately derived from carbon dioxide drawn from the atmosphere though the process of photosynthesis. "Carbon dioxide is a greenhouse gas, and enhanced export of carbon to the deep ocean in the bodies of diatoms is an important natural mechanism by which the ocean regulates atmospheric carbon dioxide and our climate," says team member Dr Alex Poulton of NOCS.
The researchers believe that their findings will have an impact on modelling and satellite studies of the Madagascar bloom. "Future research will also need to account for the magnitude of carbon export associated with diatoms and their nitrogen-fixing guests in the southwest Indian Ocean, and indeed other subtropical oceanic settings," says Dr Poulton.
National Oceanography Centre, Southampton (UK)
Nitrogen-fixing bacteria convert atmospheric nitrogen into nitrogen compounds that organisms can then use as food. This process is thought to be important in areas of the ocean where nitrogen-based nutrients are otherwise in short supply, and the researchers confirm that this is indeed the case in the region south of Madagascar.
But there were some surprises. Previously, it has been thought that the large-scale autumn bloom that develops in this region is driven by nitrogen-fixing blue-green algae, or cyanobacteria, called Trichodesmium, colonies of which the researchers found to be abundant. However, the 2005 bloom was dominated by a diatom - a type of phytoplankton - the cells of which play host to another nitrogen-fixing cyanobacterium called Richella intracellularis, with Trichodesmium apparently playing second fiddle.
Diatoms have relatively large cells, and when they die they sink down the water column, carrying with them carbon that is ultimately derived from carbon dioxide drawn from the atmosphere though the process of photosynthesis. "Carbon dioxide is a greenhouse gas, and enhanced export of carbon to the deep ocean in the bodies of diatoms is an important natural mechanism by which the ocean regulates atmospheric carbon dioxide and our climate," says team member Dr Alex Poulton of NOCS.
The researchers believe that their findings will have an impact on modelling and satellite studies of the Madagascar bloom. "Future research will also need to account for the magnitude of carbon export associated with diatoms and their nitrogen-fixing guests in the southwest Indian Ocean, and indeed other subtropical oceanic settings," says Dr Poulton.
National Oceanography Centre, Southampton (UK)
Nitrogen Fixation Current Events and Nitrogen Fixation News RSSIron controls patterns of nitrogen fixation in the Atlantic
Scientists including researchers from the National Oceanography Centre, Southampton and the University of Essex have discovered that interactions between iron supply, transported through the atmosphere from deserts, and large-scale oceanic circulation control the availability of a crucial nutrient, nitrogen, in the Atlantic.
Caltech researchers reveal unexpected sources of nitrogen fixation
Researchers at the California Institute of Technology (Caltech) have identified an unexpected metabolic ability within a symbiotic community of microorganisms that may help solve a lingering mystery about the world's nitrogen-cycling budget.
Mystery Solved: Marine Microbe Is Source of Rare Nutrient
A new study of microscopic marine microbes, called phytoplankton, by researchers at Woods Hole Oceanographic Institution (WHOI) and the University of South Carolina has solved a ten-year-old mystery about the source of an essential nutrient in the ocean.
Nitrogen research shows how some plants invade, take over others
Biologists know that when plants battle for space, often the actual battle is for getting the nitrogen.
Scientists sequence genome of the N2-fixing, soil-living bacterium Azotobacter vinelandii
A collaboration of researchers, which includes scientists at the Virginia Bioinformatics Institute (VBI) and Virginia Tech, have completed the genome sequence of Azotobacter vinelandii, uncovering important genetic information that will contribute to a more complete understanding of the biology of this versatile, soil-living bacterium.
New images of marine microbe illuminate carbon and nitrogen fixation
Trichodesmium is unusual among marine microbes because it both "breathes" carbon dioxide like plants, while also taking nitrogen gas from the air and "fixing" it into a fertilizer of the seas.
As Andean glacier retreats, tiny life forms swiftly move in, CU-Boulder study shows
A University of Colorado at Boulder team working at 16,400 feet in the Peruvian Andes has discovered how barren soils uncovered by retreating glacier ice can swiftly establish a thriving community of microbes, setting the table for lichens, mosses and alpine plants.
Outflow from World's Largest River - the Amazon - Powers Atlantic Ocean Carbon
Nutrients from the Amazon River's outflow spread well beyond the continental shelf and drive carbon cycling in the tropical ocean, say scientists who conducted a multi-year study. They will publish their results this week online in the journal Proceedings of the National Academy of Sciences (PNAS).
Amazon powers tropical ocean's carbon sink
Nutrients from the Amazon River spread well beyond the continental shelf and drive carbon capture in the deep ocean, according to the authors of a multi-year study.
Scientists may have solved an ecological riddle
A team of scientists may have solved the riddle of why plants that work with bacteria to convert atmospheric nitrogen gas into an essential biological nutrient (ammonia) tend to prevail in the world's tropical regions rather than higher latitudes.
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Nitrogen Fixation by John Postgate (Author) The fixation of nitrogen--the conversion of atmospheric nitrogen to a form that plants can use--is fundamental to the productivity of the biosphere and therefore to the ability of the expanding human population to feed itself. Although the existence and importance of the process of biological nitrogen fixation has been recognized for more than a century, scientific advances over the past few decades have radically altered our understanding of its nature and mechanisms. This book provides an introductory-level survey of biological nitrogen fixation, covering the role of the process in the global nitrogen cycle as well as its biochemistry, physiology, genetics, ecology, general biology and prospects for its future exploitation. This new edition has been fully updated to include the most... |
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Revolution by Alex Tamayo Wolf (Author) In the beautiful countryside outside imperial Vienna, in the years leading up to World War I, a remarkable story took place... Helene Marie Neumann, a vintner's daughter, spends her youth making wine with her mother and father, soaking up the Riesling sunshine, growing into a lovely young woman. Here she meets Maximilian Rieger, a wealthy boy whose family owns a nearby villa. They become good friends. But dark clouds roll in on this idyllic life. Maximilian is sent away to boarding school. And Maximilian's father, a ruthless businessman, swindles the vineyard from Helene's father, the town drunk. The vineyard lost, Helene is taken to an orphanage in the slums of Vienna, forced into prostitution, and remains there until she is eighteen. On the darkest day of her life, she finds a seed... |
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