{"id":187,"date":"2017-01-23T16:35:45","date_gmt":"2017-01-23T16:35:45","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/chapter\/5-4-dissolved-gases-oxygen\/"},"modified":"2021-10-25T21:49:45","modified_gmt":"2021-10-25T21:49:45","slug":"5-4-dissolved-gases-oxygen","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/chapter\/5-4-dissolved-gases-oxygen\/","title":{"raw":"5.4 Dissolved Gases: Oxygen","rendered":"5.4 Dissolved Gases: Oxygen"},"content":{"raw":"[pb_glossary id=\"872\"]Ions [\/pb_glossary] are not the only materials that are dissolved in seawater. The oceans also contain dissolved gases that are very important to living organisms, particularly oxygen (O<sub>2<\/sub>), carbon dioxide (CO<sub>2<\/sub>), and nitrogen (N<sub>2<\/sub>). Oxygen is required for respiration in marine plants, algae, and [pb_glossary id=\"1028\"]phytoplankton [\/pb_glossary] (the primary producers) and animals. Carbon dioxide is utilized by the primary producers to power [pb_glossary id=\"1024\"]photosynthesis[\/pb_glossary], a byproduct of which is oxygen. Nitrogen gas dissolved in the ocean is fixed by bacteria and converted into the forms required for [pb_glossary id=\"1603\"]primary production[\/pb_glossary], such as nitrate and nitrite.\r\n\r\nAll of these gases are found in the atmosphere, and can enter the ocean by dissolving into the water at the ocean\u2019s surface. But the amount of each gas in air is very different from the amount found in the ocean (Table 5.4.1).\r\n\r\n[table id=6 \/]\r\n\r\nThe amount of each gas that can dissolve in the ocean depends on the solubility and saturation of the gas in water. <strong>[pb_glossary id=\"1156\"]Solubility [\/pb_glossary]<\/strong> refers to the amount of a dissolved gas that the water can hold under a particular set of conditions, which are usually defined as 0<sup>o<\/sup> C and 1 atmosphere of pressure. The solubility of a gas increases with increasing pressure, decreased temperature, and decreased salinity. <strong>[pb_glossary id=\"1102\"]Saturation [\/pb_glossary]<\/strong> refers to the amount of gas currently dissolved in the water, relative to the maximum possible content. If the water is undersaturated, more gas can dissolve. If the water is saturated or supersaturated, gas may be released. Most atmospheric gases are saturated in the ocean, but O<sub>2<\/sub> and CO<sub>2<\/sub> are not saturated because they are rapidly used by living organisms.\r\n\r\n<strong>Oxygen<\/strong>\r\n\r\nTypical oceanic dissolved oxygen profiles are shown in Figure 5.4.1. The shape of the profile is determined by the various processes that add or remove oxygen from the water at different depths.\r\n\r\nOxygen content is highest at the surface for two main reasons; this is where oxygen dissolves into the ocean from the atmosphere, and the surface water is where oxygen is produced by [pb_glossary id=\"1028\"]phytoplankton[\/pb_glossary] through [pb_glossary id=\"1024\"]photosynthesis[\/pb_glossary]. Respiration is also occurring in the surface waters, but the rate of photosynthetic oxygen production is greater than the rate of removal through respiration. It should be noted that even though dissolved oxygen is highest at the surface, there is still far less oxygen in the water than is found in the air. Well-oxygenated surface water may only contain around 8 mg O<sub>2<\/sub>\/l, while the air contains 210 mg O<sub>2<\/sub>\/l.\r\n\r\nAs depth increases, dissolved oxygen declines, reaching a minimum between a few hundred meters and 1000 m deep, the aptly-named <strong>[pb_glossary id=\"1004\"]oxygen minimum layer[\/pb_glossary]<\/strong>. At these depths and below, the water is too far removed from the surface for any atmospheric exchange, and there is not enough light to support photosynthesis, so there is little if any oxygen added to the water. At the same time, oxygen is removed from the water through the respiration of deep water organisms, and the decomposition of organic material by bacteria as it sinks to depth.\r\n\r\nBelow the oxygen minimum layer there is often an increase in dissolved oxygen at the greatest depths (Figures 5.4.1, 5.4.2). This bottom water is usually colder than the surface water and is under enormous pressure; as stated above,\u00a0lower temperatures and higher pressure increase the solubility of dissolved gases. But there is another reason that bottom water contains more oxygen than mid-water depths that has to do with the way water circulates throughout the deep ocean (see <a href=\"\/chapter\/9-8-thermohaline-circulation\/\">section 9.8<\/a>). In polar regions, the cold surface water absorbs lots of oxygen. This cold, oxygen-rich water sinks to the bottom due to its high [pb_glossary id=\"676\"]density[\/pb_glossary], taking the oxygen with it. The oxygen-rich bottom water will then spend the next thousand years or so moving over the seafloor throughout the major ocean basins. This deep water circulation is the source of oxygen for bottom-dwelling (benthic) organisms. The oxygen-rich bottom water forms in the polar regions of the Atlantic, and slowly makes its way to the Pacific, with oxygen being removed for respiration along the way. This is why dissolved oxygen levels in Pacific deep water are generally lower than in the Atlantic (Figure 5.4.1).\r\n\r\n[caption id=\"attachment_185\" align=\"aligncenter\" width=\"611\"]<a href=\"https:\/\/rwu.pressbooks.pub\/app\/uploads\/sites\/7\/2017\/01\/figure5.4.1.png\" target=\"_blank\" rel=\"noopener noreferrer\"><img class=\"wp-image-185 size-full\" src=\"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2017\/01\/figure5.4.1.png\" alt=\"Representative dissolved oxygen profiles for the Pacific and Atlantic oceans. X-axis is depth (m) and the Y-axis is dissolved oxygen (mg\/l). The Atlantic showcases higher amounts of dissolved oxygen.\" width=\"611\" height=\"633\" \/><\/a> <strong>Figure 5.4.1<\/strong> Representative dissolved oxygen profiles for the Pacific and Atlantic oceans (PW).[\/caption]\r\n\r\n[caption id=\"attachment_186\" align=\"aligncenter\" width=\"1024\"]<a href=\"https:\/\/rwu.pressbooks.pub\/app\/uploads\/sites\/7\/2019\/05\/figure5.4.2.png\" target=\"_blank\" rel=\"noopener noreferrer\"><img class=\"wp-image-186 size-large\" src=\"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-1024x463.png\" alt=\"Dissolved oxygen profile from a transect across the Atlantic Ocean from Florida to the coast of Africa (inset). The oxygen minimum layer is visible between 500-1000 m\" width=\"1024\" height=\"463\" \/><\/a> <strong>Figure 5.4.2<\/strong> Dissolved oxygen profile from a transect across the Atlantic Ocean from Florida to the coast of Africa (inset). The oxygen minimum layer is visible between 500-1000 m (eWOCE, http:\/\/www.ewoce.org\/gallery\/eWOCE_Tables.html#Atlantic).[\/caption]\r\n\r\nAreas where dissolved oxygen levels are too low to support most life are referred to as <strong>[pb_glossary id=\"850\"]hypoxic [\/pb_glossary] <\/strong>zones (they are experiencing <strong>[pb_glossary id=\"850\"]hypoxia[\/pb_glossary]<\/strong>, or low oxygen). Hypoxia is usually defined as oxygen levels below 2 mg\/L. <strong>[pb_glossary id=\"542\"]Anoxic[\/pb_glossary]<\/strong> zones ([pb_glossary id=\"542\"]anoxia [\/pb_glossary]= without oxygen) show more severe forms of hypoxia, with oxygen below 0.5 mg\/L. Some parts of the oceans may experience seasonal or temporary periods of hypoxia, while in other areas these conditions may last much longer. These hypoxic conditions often lead to mass die-offs of marine organisms who struggle to survive without sufficient oxygen.\r\n\r\n<hr \/>\r\n\r\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Additional links for more information:<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<ul>\r\n \t<li>NOAA site on oceanic hypoxic zones: <a href=\"http:\/\/oceanservice.noaa.gov\/hazards\/hypoxia\/\" target=\"_blank\" rel=\"noopener noreferrer\">http:\/\/oceanservice.noaa.gov\/hazards\/hypoxia\/<\/a><\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>","rendered":"<p><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_872\">Ions <\/a> are not the only materials that are dissolved in seawater. The oceans also contain dissolved gases that are very important to living organisms, particularly oxygen (O<sub>2<\/sub>), carbon dioxide (CO<sub>2<\/sub>), and nitrogen (N<sub>2<\/sub>). Oxygen is required for respiration in marine plants, algae, and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_1028\">phytoplankton <\/a> (the primary producers) and animals. Carbon dioxide is utilized by the primary producers to power <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_1024\">photosynthesis<\/a>, a byproduct of which is oxygen. Nitrogen gas dissolved in the ocean is fixed by bacteria and converted into the forms required for primary production, such as nitrate and nitrite.<\/p>\n<p>All of these gases are found in the atmosphere, and can enter the ocean by dissolving into the water at the ocean\u2019s surface. But the amount of each gas in air is very different from the amount found in the ocean (Table 5.4.1).<\/p>\n<p>[table id=6 \/]<\/p>\n<p>The amount of each gas that can dissolve in the ocean depends on the solubility and saturation of the gas in water. <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_1156\">Solubility <\/a><\/strong> refers to the amount of a dissolved gas that the water can hold under a particular set of conditions, which are usually defined as 0<sup>o<\/sup> C and 1 atmosphere of pressure. The solubility of a gas increases with increasing pressure, decreased temperature, and decreased salinity. <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_1102\">Saturation <\/a><\/strong> refers to the amount of gas currently dissolved in the water, relative to the maximum possible content. If the water is undersaturated, more gas can dissolve. If the water is saturated or supersaturated, gas may be released. Most atmospheric gases are saturated in the ocean, but O<sub>2<\/sub> and CO<sub>2<\/sub> are not saturated because they are rapidly used by living organisms.<\/p>\n<p><strong>Oxygen<\/strong><\/p>\n<p>Typical oceanic dissolved oxygen profiles are shown in Figure 5.4.1. The shape of the profile is determined by the various processes that add or remove oxygen from the water at different depths.<\/p>\n<p>Oxygen content is highest at the surface for two main reasons; this is where oxygen dissolves into the ocean from the atmosphere, and the surface water is where oxygen is produced by <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_1028\">phytoplankton<\/a> through <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_1024\">photosynthesis<\/a>. Respiration is also occurring in the surface waters, but the rate of photosynthetic oxygen production is greater than the rate of removal through respiration. It should be noted that even though dissolved oxygen is highest at the surface, there is still far less oxygen in the water than is found in the air. Well-oxygenated surface water may only contain around 8 mg O<sub>2<\/sub>\/l, while the air contains 210 mg O<sub>2<\/sub>\/l.<\/p>\n<p>As depth increases, dissolved oxygen declines, reaching a minimum between a few hundred meters and 1000 m deep, the aptly-named <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_1004\">oxygen minimum layer<\/a><\/strong>. At these depths and below, the water is too far removed from the surface for any atmospheric exchange, and there is not enough light to support photosynthesis, so there is little if any oxygen added to the water. At the same time, oxygen is removed from the water through the respiration of deep water organisms, and the decomposition of organic material by bacteria as it sinks to depth.<\/p>\n<p>Below the oxygen minimum layer there is often an increase in dissolved oxygen at the greatest depths (Figures 5.4.1, 5.4.2). This bottom water is usually colder than the surface water and is under enormous pressure; as stated above,\u00a0lower temperatures and higher pressure increase the solubility of dissolved gases. But there is another reason that bottom water contains more oxygen than mid-water depths that has to do with the way water circulates throughout the deep ocean (see <a href=\"\/chapter\/9-8-thermohaline-circulation\/\">section 9.8<\/a>). In polar regions, the cold surface water absorbs lots of oxygen. This cold, oxygen-rich water sinks to the bottom due to its high <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_676\">density<\/a>, taking the oxygen with it. The oxygen-rich bottom water will then spend the next thousand years or so moving over the seafloor throughout the major ocean basins. This deep water circulation is the source of oxygen for bottom-dwelling (benthic) organisms. The oxygen-rich bottom water forms in the polar regions of the Atlantic, and slowly makes its way to the Pacific, with oxygen being removed for respiration along the way. This is why dissolved oxygen levels in Pacific deep water are generally lower than in the Atlantic (Figure 5.4.1).<\/p>\n<figure id=\"attachment_185\" aria-describedby=\"caption-attachment-185\" style=\"width: 611px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/rwu.pressbooks.pub\/app\/uploads\/sites\/7\/2017\/01\/figure5.4.1.png\" target=\"_blank\" rel=\"noopener noreferrer\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-185 size-full\" src=\"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2017\/01\/figure5.4.1.png\" alt=\"Representative dissolved oxygen profiles for the Pacific and Atlantic oceans. X-axis is depth (m) and the Y-axis is dissolved oxygen (mg\/l). The Atlantic showcases higher amounts of dissolved oxygen.\" width=\"611\" height=\"633\" srcset=\"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2017\/01\/figure5.4.1.png 611w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2017\/01\/figure5.4.1-290x300.png 290w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2017\/01\/figure5.4.1-65x67.png 65w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2017\/01\/figure5.4.1-225x233.png 225w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2017\/01\/figure5.4.1-350x363.png 350w\" sizes=\"auto, (max-width: 611px) 100vw, 611px\" \/><\/a><figcaption id=\"caption-attachment-185\" class=\"wp-caption-text\"><strong>Figure 5.4.1<\/strong> Representative dissolved oxygen profiles for the Pacific and Atlantic oceans (PW).<\/figcaption><\/figure>\n<figure id=\"attachment_186\" aria-describedby=\"caption-attachment-186\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/rwu.pressbooks.pub\/app\/uploads\/sites\/7\/2019\/05\/figure5.4.2.png\" target=\"_blank\" rel=\"noopener noreferrer\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-186 size-large\" src=\"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-1024x463.png\" alt=\"Dissolved oxygen profile from a transect across the Atlantic Ocean from Florida to the coast of Africa (inset). The oxygen minimum layer is visible between 500-1000 m\" width=\"1024\" height=\"463\" srcset=\"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-1024x463.png 1024w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-300x136.png 300w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-768x347.png 768w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-1536x694.png 1536w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-2048x925.png 2048w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-65x29.png 65w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-225x102.png 225w, https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-content\/uploads\/sites\/16\/2021\/10\/figure5.4.2-350x158.png 350w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><figcaption id=\"caption-attachment-186\" class=\"wp-caption-text\"><strong>Figure 5.4.2<\/strong> Dissolved oxygen profile from a transect across the Atlantic Ocean from Florida to the coast of Africa (inset). The oxygen minimum layer is visible between 500-1000 m (eWOCE, http:\/\/www.ewoce.org\/gallery\/eWOCE_Tables.html#Atlantic).<\/figcaption><\/figure>\n<p>Areas where dissolved oxygen levels are too low to support most life are referred to as <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_850\">hypoxic <\/a> <\/strong>zones (they are experiencing <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_850\">hypoxia<\/a><\/strong>, or low oxygen). Hypoxia is usually defined as oxygen levels below 2 mg\/L. <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_542\">Anoxic<\/a><\/strong> zones (<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_187_542\">anoxia <\/a>= without oxygen) show more severe forms of hypoxia, with oxygen below 0.5 mg\/L. Some parts of the oceans may experience seasonal or temporary periods of hypoxia, while in other areas these conditions may last much longer. These hypoxic conditions often lead to mass die-offs of marine organisms who struggle to survive without sufficient oxygen.<\/p>\n<hr \/>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Additional links for more information:<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li>NOAA site on oceanic hypoxic zones: <a href=\"http:\/\/oceanservice.noaa.gov\/hazards\/hypoxia\/\" target=\"_blank\" rel=\"noopener noreferrer\">http:\/\/oceanservice.noaa.gov\/hazards\/hypoxia\/<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_187_872\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_872\"><div tabindex=\"-1\"><p>an atom or molecule that has either gained or lost electrons and has thus become charged (5.1)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_187_1028\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_1028\"><div tabindex=\"-1\"><p>drifting, usually single-celled algae that undergo photosynthesis (7.1)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_187_1024\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_1024\"><div tabindex=\"-1\"><p>the production of organic compounds from carbon dioxide and water, using sunlight as an energy source (5.5)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_187_1603\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_1603\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_187_1156\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_1156\"><div tabindex=\"-1\"><p>the amount of a dissolved substance that water can hold under a particular set of conditions, which are usually defined as 0 degrees C and 1 atmosphere of pressure (5.4)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_187_1102\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_1102\"><div tabindex=\"-1\"><p>the amount of a substance currently dissolved in the water, relative to the maximum possible content (5.4)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_187_1004\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_1004\"><div tabindex=\"-1\"><p>region of ocean depths where dissolved oxygen is at its lowest level; usually around 1000 m for the open ocean (5.4)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_187_676\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_676\"><div tabindex=\"-1\"><p>mass per unit volume of a substance (e.g., g\/cubic cm) (6.3)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_187_850\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_850\"><div tabindex=\"-1\"><p>a condition with low dissolved oxygen, usually defined as oxygen levels below 2 mg\/L (5.4)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_187_542\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_187_542\"><div tabindex=\"-1\"><p>conditions of zero or extremely low dissolved oxygen, usually below 0.5 mg\/L (5.4)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":33,"menu_order":5,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["paul-webb"],"pb_section_license":"cc-by"},"chapter-type":[],"contributor":[60],"license":[52],"class_list":["post-187","chapter","type-chapter","status-publish","hentry","contributor-paul-webb","license-cc-by"],"part":160,"_links":{"self":[{"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/pressbooks\/v2\/chapters\/187","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/wp\/v2\/users\/33"}],"version-history":[{"count":4,"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/pressbooks\/v2\/chapters\/187\/revisions"}],"predecessor-version":[{"id":1423,"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/pressbooks\/v2\/chapters\/187\/revisions\/1423"}],"part":[{"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/pressbooks\/v2\/parts\/160"}],"metadata":[{"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/pressbooks\/v2\/chapters\/187\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/wp\/v2\/media?parent=187"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/pressbooks\/v2\/chapter-type?post=187"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/wp\/v2\/contributor?post=187"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/introduction-to-oceanography\/wp-json\/wp\/v2\/license?post=187"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}