{"id":537,"date":"2016-08-02T12:26:03","date_gmt":"2016-08-02T12:26:03","guid":{"rendered":"http:\/\/blogs.nicholas.duke.edu\/citizenscientist\/?p=537"},"modified":"2016-08-02T12:26:03","modified_gmt":"2016-08-02T12:26:03","slug":"hypoxia","status":"publish","type":"post","link":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/hypoxia\/","title":{"rendered":"Hypoxia"},"content":{"rendered":"

For the past couple of decades, late summer brings a bloom of algae in the Gulf of Mexico, just off the mouth of the Mississippi River.\u00a0 Last year, the bloom covered 17000 km2<\/sup> \u2013somewhat larger than the State of Connecticut.\u00a0 When the bloom dies, the decomposition of algal biomass consumes all the oxygen dissolved in the water\u2014hypoxia. Without oxygen, fish and shellfish die. Hence, the bloom is known as the Dead Zone.<\/p>\n

Similar blooms are found at the mouth of estuaries in other regions of the world, especially when their watersheds harbor a large amount of agricultural activity. \u00a0Chesapeake Bay and the Baltic Sea are good examples, and a similar phenomenon is found in central Lake Erie. \u00a0There is evidence that hypoxia began to occur in large rivers and lakes more than 100 years ago.\u00a0 What causes hypoxic zones to occur?<\/p>\n

The answer lies in the large amount of nitrogen fertilizer used in modern agriculture, and also incidentally on home gardens and golf courses. When nitrogen fertilizer contains nitrate, it is easily lost to runoff waters, inasmuch as nitrate is highly soluble in water.\u00a0 Applications in excess of immediate plant demand are lost.\u00a0 Even when nitrogen fertilizer is applied in other forms, such as ammonium or urea, these are easily converted to nitrate by soil microbes and lost in runoff.\u00a0 By one account nearly 8-12% of the nitrogen fertilizer applied worldwide is lost from fertilized fields and transported to the sea. \u00a0In some individual fields, the value can be as high as 50%.<\/p>\n

Still more nitrogen is lost during the disposal of animal wastes from modern industrialized production of pork and chickens. Here nitrogen is lost during inadvertent overflow of waste lagoons, and nitrogen is transported to groundwater, which makes its way to stream channels.\u00a0 In North Carolina, the nitrogen isotopic composition of animal waste closely matches that in groundwater, establishing a close link between the two.<\/p>\n

When the nitrate arrives at the coastal waters, it stimulates a bloom of algae. (It is fertilizer, after all).\u00a0 This may be aided by the simultaneous transport of phosphorus from agricultural lands, although phosphorus is by no means as mobile as nitrogen when it comes to runoff waters. \u00a0The hypoxic zone in Lake Erie appears closely related to both nitrogen and phosphorus inputs.<\/p>\n

Hypoxia is one of the side-effects of modern agronomic systems which strive to feed 7 billion of us with a nutritious diet.\u00a0 Unfortunately, hypoxia saps the ocean\u2019s ability to supply protein in fish and shellfish, just at the moment that these resources are most needed by the human population. Once again, if there were fewer of us, the problem would be easier.<\/p>\n

The solution will stem from a more judicious use of fertilizer, so that the largest percentage of it is assimilated by the crop plant of interest.\u00a0 We also need to treat nitrogen and phosphorus in human and animal wastes as a resource to be recycled, not an unfortunately byproduct to be disposed.\u00a0 See my blog post at http:\/\/blogs.nicholas.duke.edu\/citizenscientist\/phosphorus-futures\/<\/a><\/p>\n

 <\/p>\n

References<\/p>\n

Blesh, J. and L.E. Drinkwater. \u00a02013. The impact of nitrogen source and crop rotation on nitrogen mass balances in the Mississippi River Basin. Ecological Applications<\/em> 23(5):1017-1035.<\/p>\n

David, M.B., L.E. Gentry, A.D. Kovacic and K.M. Smith. 1997.\u00a0 Nitrogen balance in and export from an agricultural watershed.\u00a0 Journal of Environmental Quality 26: 1038-1048.<\/p>\n

Gao, S. P. Xu, F. Zhou, H.\u00a0 Yang, C. Zheng, W. Cao, S. Tao, S. Piao, Y. Zhao, X. Ji. Z. Shang, and M. Chen. 2016.\u00a0 Quantifying nitrogen leaching response to fertilizer additions in China\u2019s cropland.\u00a0 Environmental Pollution 211: 241-251.<\/p>\n

Gardiner, J.B. and L.E. Drinkwater. 2009.\u00a0 The fate of nitrogen in grain cropping systems: a meta-analysis of 15<\/sup>N field experiments.\u00a0 Ecological Applications 19: 2167-2184.<\/p>\n

Jenny, J.-P., P. Francus, A. Normandeau, F. Lapointe, M.-E. Perga, A. Ojala, A. Schimmeimann, and B. Zolitschka. 2016.\u00a0 Global spread of hypoxia in freshwater ecosystems during the last three centuries is caused by rising local human pressure.\u00a0 Global Change Biology 22: 1481-1489.<\/p>\n

Karr, J.D., W.J. Showers, J. W. Gilliam and A. S. Andres.\u00a0 2001.\u00a0 Tracing nitrate transport and environmental impact from intensive swine farming using delta nitrogen-15.\u00a0 Journal of Environmental Quality 30: 1163-1175.<\/p>\n

Chang, C.C.Y., C. Kendall, S.R. Silva, W.A. Battaglin, and D.H. Campbell. 2002.\u00a0 Nitrate stable isotopes: tools for determining nitrate sources among different land uses in the Mississippi River Basin.\u00a0 Canadian Journal of Fisheries and Aquatic Sciences 59: 1874-1885.<\/p>\n

Rabalais, N.N., W.-J. Cai, J. Carstensen, D.J. Conley, B. Fry, X. Hu, Z. Quinones-Rivera, R. Rosenberg, C.P. Slomp, R.E. Turner, M. Voss, B. Wissel, and J. Zhang. 2014.\u00a0 Eutrophication-driven deoxygenation in the coastal ocean.\u00a0 Oceanography 27: 172-183.<\/p>\n

Schlesinger, W.H.\u00a0 2009.\u00a0 On the fate of anthropogenic nitrogen.\u00a0 Proceedings of the National Academy of Sciences.\u00a0 106:203-208.\u00a0 [doi:10.1073\/pnas.0810193105]<\/p>\n

Sebilo, M., B. Mayer, B. Nicolardot, G. Pinay, and A. Maniotti.\u00a0 2013.\u00a0 Long-term fate of nitrate fertilizer in agricultural soils.\u00a0 Proceedings of the National Academy of Sciences 110: 18185-18189<\/p>\n","protected":false},"excerpt":{"rendered":"

Hypoxia is one of the side-effects of modern agronomic systems which strive to feed 7 billion of us with a nutritious diet.<\/p>\n","protected":false},"author":517,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[99,114,5,100,88,91,96],"tags":[],"coauthors":[6],"class_list":["post-537","post","type-post","status-publish","format-standard","hentry","category-agriculture","category-biogeochemistry","category-faculty","category-lakes-and-streams","category-marine-studies","category-water","category-water-pollution"],"jetpack_publicize_connections":[],"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/s5KxUl-hypoxia","jetpack_featured_media_url":"","post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/posts\/537","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/users\/517"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/comments?post=537"}],"version-history":[{"count":1,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/posts\/537\/revisions"}],"predecessor-version":[{"id":538,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/posts\/537\/revisions\/538"}],"wp:attachment":[{"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/media?parent=537"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/categories?post=537"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/tags?post=537"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/coauthors?post=537"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}