{"id":5945,"date":"2015-08-27T17:09:53","date_gmt":"2015-08-27T17:09:53","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=5945"},"modified":"2015-08-27T17:09:53","modified_gmt":"2015-08-27T17:09:53","slug":"intensity-of-desert-storms-may-affect-ocean-phytoplankton","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/intensity-of-desert-storms-may-affect-ocean-phytoplankton\/","title":{"rendered":"Intensity of desert storms may affect ocean phytoplankton"},"content":{"rendered":"

MIT study finds phytoplankton are extremely sensitive to changing levels of desert dust.<\/strong><\/em><\/p>\n

\"A<\/a>
A 2012 satellite image shows a dust storm blowing over the Sea of Japan out to the North Pacific.
Courtesy of NASA<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. —\u00a0Each spring, powerful dust storms in the deserts of Mongolia and northern China send thick clouds of particles into the atmosphere. Eastward winds sweep these particles as far as the Pacific, where dust ultimately settles in the open ocean. This desert dust contains, among other minerals, iron \u2014 an essential nutrient for hundreds of species of phytoplankton that make up the ocean\u2019s food base.<\/p>\n

Now scientists at MIT, Columbia University, and Florida State University have determined that once iron is deposited in the ocean, it has a very short residence time, spending only six months in surface waters before sinking into the deep ocean. This high turnover of iron signals that large seasonal changes in desert dust may have dramatic effects on surface phytoplankton that depend on iron.<\/p>\n

\u201cIf there are changes to the sizes of deserts in Asia, or changes in the way people are using land, there could be a larger source of dust to the ocean,\u201d says Chris Hayes, a postdoc in MIT\u2019s Department of Earth, Atmospheric, and Planetary Sciences (EAPS). \u201cIt\u2019s difficult to predict how the whole ecosystem will change, but because the residence time [of iron] is very short, year-to-year changes in dust will definitely have an impact on phytoplankton.\u201d<\/p>\n

The team\u2019s results are published in the journal\u00a0Geochemica et Cosmochimica Acta.\u00a0<\/em>Co-authors include Ed Boyle, a professor of ocean geochemistry at MIT; David McGee, the Kerr-McGee Career Development Assistant Professor in EAPS; and former postdoc Jessica Fitzsimmons.<\/p>\n

Dust to dust<\/strong><\/p>\n

Certain species of phytoplankton, such as cyanobacteria, require iron as a main nutrient to fuel nitrogen fixation and other growth-related processes. Hayes estimates that up to 40 percent of the ocean contains phytoplankton species whose growth is limited by the amount of iron available.<\/p>\n

As desert dust is one of the only sources of oceanic iron, Hayes wanted to see to what extent changing levels of dust would have an effect on iron concentrations in seawater: Does iron stick around in surface waters for long periods, thereby making phytoplankton less sensitive to changes in incoming dust? Or does the mineral make a short appearance before sinking to inaccessible depths, making phytoplankton depend much more on seasonal dust?<\/p>\n

To get answers, Hayes and his colleagues traveled to Hawaii to collect ocean samples at a station called ALOHA, the site of a long-term oceanography program conducted by the University of Hawaii. In September 2013, the team took a half-day cruise into open ocean, and then spent two weeks collecting samples of ocean water at varying depths.<\/p>\n

The researchers acidified the samples and transported them back to the lab at MIT, where they analyzed the water for both iron and thorium \u2014 a chemical element that is found in dust alongside iron. As it\u2019s difficult to determine the rate at which iron sinks from the ocean\u2019s surface to deep waters, Hayes reasoned that thorium might be a reasonable proxy.<\/p>\n

[pullquote]Thorium has a number of isotopes: Thorium-232 is typically found in dust, and thorium-230 is produced from the decay of uranium, which decays to thorium at the same rate throughout the ocean.[\/pullquote]\u00a0By comparing the amount of thorium-230 detected in ocean samples to the amount produced by uranium decay, Hayes was able to calculate thorium\u2019s removal rate, or the time it takes for the chemical to sink after settling on the ocean\u2019s surface.<\/p>\n

This removal rate, he reasoned, is equivalent to the input rate of dust, or the rate at which dust is supplied to an ocean region. As the composition of an average desert dust particle is known, Hayes then extrapolated the input rate to estimate iron\u2019s residence time in surface waters.<\/p>\n

A small piece of a big question<\/strong><\/p>\n

The team found that on average, iron tends to stay within 150 meters of the ocean\u2019s surface \u2014 the layer in which phytoplankton resides \u00ad\u2014 for about six months before accumulating on larger particles and sinking to the deep ocean. This residence time leaves a relatively short period for phytoplankton to absorb iron, making the organisms rather sensitive to any changes in incoming desert dust.<\/p>\n

\u201cDust can change a lot from season to season \u2014 by an order of magnitude,\u201d Hayes says. \u201cFrom satellite images, you can see big pulses of dust coming from these deserts. That could change with climate change, and different precipitation patterns. So we\u2019re trying to keep track: If it does change, will it have an impact?\u201d<\/p>\n

As phytoplankton play a natural role in removing carbon dioxide from the atmosphere, better estimates of iron residence times, and desert dust inputs to the ocean, may help scientists gauge phytoplankton\u2019s role in combating climate change.<\/p>\n

\u201cIt\u2019s a very small part that we\u2019re getting more quantitative about,\u201d Hayes says. \u201cIt\u2019s one piece that adds to trying to make the prediction: If there\u2019s more dust, will the ocean take up more carbon? That\u2019s a big-picture question that we can\u2019t totally answer with this, but we have one piece on the way to answering that.\u201d<\/p>\n

This research was funded in part by the National Science Foundation.<\/p>\n","protected":false},"excerpt":{"rendered":"

Each spring, powerful dust storms in the deserts of Mongolia and northern China send thick clouds of particles into the atmosphere. Eastward winds sweep these particles as far as the Pacific, where dust ultimately settles in the open ocean. This desert dust contains, among other minerals, iron \u2014 an essential nutrient for hundreds of species of phytoplankton that make up the ocean\u2019s food base.<\/p>\n","protected":false},"author":2,"featured_media":5946,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-5945","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/08\/MIT-Mineral-Dust-1.jpg",150,100,false]},"author_info":{"info":["RevoScience"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/5945","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=5945"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/5945\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/5946"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=5945"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=5945"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=5945"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}