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.
Roughly a decade ago scientists discovered a rare form of organic phosphorus in marine organic matter. Not only were the researchers surprised to find this form of phosphorus, called phosphonate, but the concentrations in which it was found were very high, throughout the ocean. Scientists hypothesized that phosphonate is produced and consumed in the ocean, but no one understood where it came from and why it was so abundant.
Enter Trichodesmium. In 2006, WHOI biologist Sonya Dyhrman along with other WHOI colleagues initiated a field and laboratory study with this phytoplankton group, which is plentiful in low-nutrient warm tropical and subtropical waters. They discovered that Tricodesmium uses phosphonate to fuel its biological processes, including the fixation of carbon and nitrogen.
Their finding was unexpected because, chemically, phosphonate has a very strong carbon-phosphorus bond that requires a lot of energy, and a special set of genes, for Trichodesmium to break.
But Dyhrman and her colleagues's discovery that Trichodesmium could use this form of phosphorus to support carbon and nitrogen fixation still didn't solve the basic mystery: where were the high concentrations of this rare compound coming from?
Now, a study newly published in Nature Geoscience by Dyhrman and her colleague Claudia Benitez-Nelson, a marine geochemist with the University of South Carolina, has solved the long-standing mystery.
"We've been fascinated by these phosphonate compounds for a while," said Benitez-Nelson. "Sonya and I decided that something had to be producing them, and we had to start looking at all these organisms to figure out
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Woods Hole Oceanographic Institution