New Source of Iron May Change Our Understanding of Marine Food Web

Written by on June 4, 2014 in Other News

Researchers recently discovered a new source of iron in the oceans — meltwater from ice sheets — that may impact our understanding of marine food chains and climate change.

Melt water in NW Greenland.

Meltwater in NW Greenland. Photo credit: NOAA.

Due to its impact on ocean productivity, iron is considered one of the most important biochemical elements. However, most of Earth’s supply of iron isn’t biologically available because it’s primarily found as an unreactive mineral in natural waters. Bioavailable iron isn’t all that common.

Iron is known to boost phytoplankton growth in many of the Earth’s oceans. Phytoplankton capture carbon, which buffers the effects of global warming, and act as a major food source at the base of the marine food web. The discovery that summer meltwaters from ice sheets are rich in bioavailable iron, therefore, could have major implications on both our predictions for climate change and our understanding of marine food chains.

“The Greenland and Antarctic Ice Sheets cover around 10% of global land surface. Iron exported in icebergs from these ice sheets have been recognized as a source of iron to the oceans for some time. Our finding that there is also significant iron discharged in runoff from large ice sheet catchments is new,” Jon Hawkings of the University of Bristol explained in a news release.

This means that relatively high iron concentrations are released from the ice sheet all summer, providing a continuous source of iron to the coastal ocean.

The research team estimates that the flux of bioavailable iron associated with glacial runoff is between 400,000 and 2.5 million tons per year in Greenland alone. In Antarctica, it totals between 60,000 and 100,000 tons per year. Combined, that’s like adding the weight of 3,000 fully-loaded Boeing 747s to the ocean every year.

“This is a substantial release of iron from the ice sheet,” Hawkings noted.

It will be localized to the Polar Regions, but the impact is sure to be bigger than that.

“Researchers have already noted that glacial meltwater run-off is associated with large phytoplankton blooms – this may help to explain why.”

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Copyright © 2014 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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