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New evidence from the Atlantic seafloor has produced some answers.<\/p>\n
Plankton with armor<\/p>\n
These cells are coccolithophores<\/a>, microscopic ocean organisms that have plant-like characteristics. They wrap themselves in overlapping plates of calcite, a stable form of calcium carbonate. <\/p>\n Those plates, called coccoliths, are made of the same stuff found in limestone<\/a>. Each cell is smaller than the width of a human hair.<\/p>\n When these cells die, their calcite plates drift down and settle on the seafloor, locking away carbon for hundreds of thousands of years. That slow rain of minerals helps set how much carbon dioxide stays in the air. <\/p>\n This can affect the Earth\u2019s carbon cycle over long stretches of geological time. So, a great deal of Earth\u2019s chemistry rides on these specks. The trouble has always been figuring out what makes them produce more calcite or less. <\/p>\n Lab studies grew single strains in tanks and learned plenty, but a tank is not an ocean. Stretching those tidy results out to the messy real world, and back across millions of years, never quite worked.<\/p>\n Reading the mud<\/p>\n A team led by researchers at the University of Oxford (Oxford<\/a>) decided to skip the tanks and read the seafloor directly. <\/p>\n They pulled up well-preserved sediment from a long line of sites running north to south across the Atlantic Ocean, from cold subpolar water down to the tropics.<\/p>\n Under the microscope, the buried coccoliths still held their shape. The team measured how many there were, how big, how thick, and how heavy. <\/p>\n From those measurements they worked backward to estimate how fast the original cells grew and how hard they worked at building calcite.<\/p>\n Alba Gonzalez-Lanchas, the study\u2019s lead author and a researcher at Oxford Earth Sciences, said the approach leans on long-standing microscope methods rather than anything novel. <\/p>\n That ordinariness is part of the point. The tools have been around for decades; nobody had used them quite this way to rebuild the biology of these cells from old sediment and assess the consequences for the carbon cycle.<\/p>\n A split in strategy<\/p>\n Sorting the cells into two camps revealed something the field had not seen this clearly in nature. One camp is small and fast-growing. The other is larger and naturally builds heavier plates. The two behave like opposites when conditions get good.<\/p>\n When temperature, light, and nutrients lined up well for the small fast growers, they pumped out their most heavily armored plates. <\/p>\n Growth and calcification rose together, in step. For these little cells, the ocean appears to hand over carbon fast enough to keep up with everything they\u2019re doing at once.<\/p>\n The larger cells went the other way. When they hit their peak abundance and grew fastest, their plates got thinner, not thicker. Their apparent hunger for carbon likely ran ahead of what the water could deliver.<\/p>\n Push them to grow quickly and their calcite-building<\/a> seems to fall behind \u2013 a trade-off<\/a> between what a cell needs and what its surroundings can supply.<\/p>\n A line at forty north<\/p>\n The two camps don\u2019t mix evenly across the ocean. The team found a divide running across the Atlantic at roughly 40 degrees north, about the latitude of New York or Lisbon. It splits the sea into two zones with two different rulers.<\/p>\n North of that line, in colder and more churned-up water, the large heavily plated species dominate calcite production. <\/p>\n South of it, through the milder mid-latitudes and subtropics, the small fast growers take over. The handoff is surprisingly sharp for something spread across open ocean.<\/p>\n That boundary tracks the big environmental gradients in the Atlantic \u2013 shifts in temperature, in nutrients, and in the carbon chemistry of the seawater itself. Researchers read it as a border between two ways of making calcite. <\/p>\n To the north, the speed of the chemical reaction inside the cell sets the pace. To the south, the bottleneck appears to be how fast carbon can physically move into the cell<\/a> in the first place.<\/p>\n Why the shapes differ<\/p>\n The two building styles even show up in the shape of the plates, and there\u2019s a rough parallel with how snowflakes form.<\/p>\n Small cells churn out lacy, branching crystals \u2013 the mark of a cell building faster than carbon can reach the spot where calcite forms. Speed wins. Detail suffers.<\/p>\n Larger, slower cells take their time. Carbon has room to gather and pack into solid, space-filling plates before the next one starts. <\/p>\n Their slower pace is exactly what lets them build the heavier, denser armor. Less a flaw than a different schedule.<\/p>\n This connects cell size, growth speed, and the carbon chemistry of the surrounding water into one picture. <\/p>\n A study<\/a> of these organisms\u2019 body measurements laid the groundwork, but linking the physical shape of a coccolith to the carbon conditions that produced it is newer ground, and it\u2019s what lets the buried plates speak.<\/p>\n Fossils as climate records<\/p>\n What\u2019s new here is a way to pull living biology out of dead sediment. Until this study, the link between ocean conditions, cell physiology, and calcite output stayed locked in lab tanks. <\/p>\n Now, researchers can estimate growth rates and calcification from fossil plates alone, and a framework<\/a> for doing it consistently is on the table.<\/p>\n That gives scientists a sharper tool for reading ancient climate. Buried coccoliths become a record of how these cells answered past swings in ocean chemistry and the carbon cycle \u2013 swings that the planet has been through many times before our own.<\/p>\n Climate change adds urgency to that record. As seas warm and their chemistry shifts with rising carbon dioxide, the balance between carbon supply and what cells need to calcify could tip, and the 40-degree line could slide. <\/p>\n Which cells will dominate tomorrow\u2019s ocean, and how much calcite they will bury, may not match what the seafloor records today.<\/p>\n The study is published in Nature Communications<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read?\u00a0Subscribe to our newsletter\u00a0<\/a>for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on\u00a0EarthSnap\u00a0<\/a>, a free app brought to you by\u00a0Eric Ralls\u00a0<\/a>and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"The ocean handles more of Earth\u2019s carbon chemistry than most people realize, and most of it happens invisibly.…\n","protected":false},"author":2,"featured_media":487300,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[61,60,82],"class_list":["post-487299","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-ie","tag-ireland","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/487299","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=487299"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/487299\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/487300"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=487299"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=487299"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=487299"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}