{"id":3617,"date":"2021-04-14T14:31:00","date_gmt":"2021-04-14T14:31:00","guid":{"rendered":"https:\/\/sites.nicholas.duke.edu\/cassar\/?p=3617"},"modified":"2021-04-20T20:32:27","modified_gmt":"2021-04-20T20:32:27","slug":"machine-learning-estimates-of-global-marine-n2-fixation","status":"publish","type":"post","link":"https:\/\/sites.nicholas.duke.edu\/cassar\/machine-learning-estimates-of-global-marine-n2-fixation\/","title":{"rendered":"Machine-learning estimates of global marine N2 fixation and diazotrophs"},"content":{"rendered":"<span class=\"embed-youtube\" style=\"text-align:center; display: block;\"><iframe loading=\"lazy\" class=\"youtube-player\" width=\"676\" height=\"381\" src=\"https:\/\/www.youtube.com\/embed\/QSqN4-ogGNc?version=3&#038;rel=1&#038;showsearch=0&#038;showinfo=1&#038;iv_load_policy=1&#038;fs=1&#038;hl=en-US&#038;autohide=2&#038;wmode=transparent\" allowfullscreen=\"true\" style=\"border:0;\" sandbox=\"allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox\"><\/iframe><\/span>\n\n\n\n<p class=\"has-text-align-center has-light-gray-color has-text-color has-small-font-size\">Machine-learning (random forest) estimate of depth-integrated N2 fixation and nifH gene distribution (Tang et al. 2019, Tang &amp; Cassar 2019)<\/p>\n\n\n\n<p><\/p>\n\n\n\n<p>Marine nitrogen (N<sub>2<\/sub>) fixation supplies \u201cnew\u201d nitrogen to the global ocean, supporting &nbsp;uptake and sequestration of carbon. Despite its central role, marine N<sub>2<\/sub> fixation and its controlling factors remain elusive. In this study, we compile over 1,100 published observations to identify the dominant predictors of marine N<sub>2<\/sub> fixation and derive global estimates based on the machine learning algorithms of random forest (RF) and support vector regression (SVR). We find that no single environmental property predicts N<sub>2<\/sub> fixation at global scales. Our RF and SVR algorithms, trained with sampling coordinates and month, solar radiation, wind speed, sea surface temperature, sea surface salinity, surface nitrate, surface phosphate, surface excess phosphorus, minimum oxygen in upper 500 m, photosynthetically available radiation (PAR), mixed layer depth, averaged PAR in the mixed layer, and chlorophyll-<em>a <\/em>concentration, estimate global marine N<sub>2<\/sub> fixation ranging from 68 to 90 Tg N yr<sup>-1<\/sup>. Comparison of our machine learning estimates and 11 other model outputs currently available in literature shows substantial discrepancies in the global magnitude and spatial distribution of marine N<sub>2<\/sub> fixation, especially in the tropics and in high latitudes. The large uncertainties in marine N<sub>2<\/sub> fixation highlighted in our study argue for increased and more coordinated efforts using geochemical tracers, modeling, and observations over broad ocean regions.<\/p>\n\n\n\n<p>See <a href=\"https:\/\/agupubs.onlinelibrary.wiley.com\/doi\/full\/10.1029\/2018JG004828\" target=\"_blank\" rel=\"noreferrer noopener\">Tang et al. (2019) <\/a>and <a rel=\"noreferrer noopener\" href=\"https:\/\/agupubs.onlinelibrary.wiley.com\/doi\/10.1029\/2019GL084376?campaign=topicalert&amp;topicscope=2dc820d3-3443-3933-98f0-0c9f57556905.4a75c07e-8776-33ce-8757-773d19c55d82\" target=\"_blank\">Tang &amp; Cassar (2019)<\/a> for more information.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"486\" data-attachment-id=\"3620\" data-permalink=\"https:\/\/sites.nicholas.duke.edu\/cassar\/machine-learning-estimates-of-global-marine-n2-fixation\/picture1\/\" data-orig-file=\"https:\/\/sites.nicholas.duke.edu\/cassar\/files\/2019\/03\/Picture1.jpg\" data-orig-size=\"1240,589\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}\" data-image-title=\"Global Marine N2 Fixation\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/sites.nicholas.duke.edu\/cassar\/files\/2019\/03\/Picture1-1024x486.jpg\" src=\"https:\/\/sites.nicholas.duke.edu\/cassar\/files\/2019\/03\/Picture1-1024x486.jpg\" alt=\"\" class=\"wp-image-3620\" srcset=\"https:\/\/sites.nicholas.duke.edu\/cassar\/files\/2019\/03\/Picture1-1024x486.jpg 1024w, https:\/\/sites.nicholas.duke.edu\/cassar\/files\/2019\/03\/Picture1-300x143.jpg 300w, https:\/\/sites.nicholas.duke.edu\/cassar\/files\/2019\/03\/Picture1-768x365.jpg 768w, https:\/\/sites.nicholas.duke.edu\/cassar\/files\/2019\/03\/Picture1-676x321.jpg 676w, https:\/\/sites.nicholas.duke.edu\/cassar\/files\/2019\/03\/Picture1.jpg 1240w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Machine-learning (random forest) estimate of depth-integrated N2 fixation and nifH gene distribution (Tang et al. 2019, Tang &amp; Cassar 2019) Marine nitrogen (N2) fixation supplies \u201cnew\u201d nitrogen to the global [&hellip;]<\/p>\n","protected":false},"author":1421,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_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}},"categories":[5],"tags":[],"class_list":["post-3617","post","type-post","status-publish","format-standard","hentry","category-lab-news","post-preview"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9c288-Wl","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/posts\/3617","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/users\/1421"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/comments?post=3617"}],"version-history":[{"count":13,"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/posts\/3617\/revisions"}],"predecessor-version":[{"id":4212,"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/posts\/3617\/revisions\/4212"}],"wp:attachment":[{"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/media?parent=3617"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/categories?post=3617"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sites.nicholas.duke.edu\/cassar\/wp-json\/wp\/v2\/tags?post=3617"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}