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Fuente: Google im\u00e1genes<\/span><\/p>\n \u00a1Vaya lio en el que me he metido al elegir la noticia para redactar este post! Como podr\u00e9is observar, el t\u00edtulo de la nota de prensa ya es de por s\u00ed confuso y confundente, sin que pueda o sepa evitarlo. Todo comenz\u00f3 con dos noticias en ingl\u00e9s que de por si se me antojaron interesantes en una primera lectura, aunque resultaron ser semi-cl\u00f3nicas.\u00a0 Sin embargo, todo apunta a que comienza a ser una pauta asumida a la hora de divulgar los resultados de un estudio, como tambi\u00e9n incluir, de cualquier modo, el cambio clim\u00e1tico<\/span><\/strong> y, de paso, a los fertilizantes<\/strong><\/span>. El art\u00edculo publicado tan solo intentaba explicar las causas de <\/span>la extinci\u00f3n en masa ocurrida en los oc\u00e9anos entre el<\/span><\/a>\u00a0 <\/span>Cenomaniense y el Turoniense <\/span><\/a>\u00a0(<\/span>Evento An\u00f3xico-2 o Evento Bonarelli<\/span><\/a>). Y escog\u00ed la noticia debido a que ten\u00eda que ver con los suelos\/regolitos\/procesos de alteraci\u00f3n<\/span><\/strong>. Pero luego entre unos y otros, as\u00ed como las consabidas llamadas de atenci\u00f3n al lector (reclamos publicitarios), terminaron por dejar la esencia de los resultados en un segundo plano. Veamos si puedo ser breve y luego os le\u00e9is el material en suajili y espa\u00f1ol-castellano que he ido recopilando.\u00a0 <\/span><\/p>\n Los nutrientes que albergan los oc\u00e9anos son en gran parte generados por los procesos de alteraci\u00f3n litosf\u00e9rica de la superficie terrestre emergida, es decir desprendidos \u00a0por suelos, regolitos y rocas, tras su alteraci\u00f3n biogeoqu\u00edmica. Estos son lavados por las aguas hasta las cuencas de drenaje que terminan por depositarlos en los mares del mundo<\/strong><\/span>. Sin ellos, la vida marina ser\u00eda muy pobre por falta de nutrimentos, a excepci\u00f3n de los dimanados por el vulcanismo<\/strong><\/span>. Sin embargo, en condiciones excepcionales, pueden liberarse en ingentes cantidades <\/span><\/strong>(ver alguna informaci\u00f3n al respecto en el material de las notas de prensa que os dejo abajo y especialmente en las anglosajonas) ocasionando la eutrofizaci\u00f3n<\/strong> <\/span>del l\u00edquido elemento (demasiados nutrientes) y como corolario, una elevada producci\u00f3n de biomasa por el fitoplancton, pudiendo dar lugar a la aparici\u00f3n de inmensas<\/strong> <\/span><\/span>floraciones algales<\/span><\/a> de alguna clase. Estas consumen<\/strong> <\/span><\/span>el ox\u00edgeno causando<\/span><\/a>condiciones de anoxia<\/span><\/a> (escasez de ox\u00edgeno) que no puede soportar la vida marina <\/span><\/strong>(los ya conocidos como \u201c<\/span>puntos muertos<\/span><\/a>\u201d) y por tanto desaparece,<\/span> comenzando una extinci\u00f3n en masa<\/span><\/strong>. La biomasa muerta cae as\u00ed hacia los fondos marinos, en donde se acumulan descomunales cantidades de materia org\u00e1nica (necromasa) en su lecho <\/span><\/strong>(ya que la anoxia evita, en gran medida, su descomposici\u00f3n, al acabarse el ox\u00edgeno). La noticia de marras por ejemplo, nos informa de pizarras oscuras muy ricas en materia org\u00e1nica que se intercalan en las columnas estratigr\u00e1ficas entre otros sedimentos m\u00e1s claros (condiciones normales).\u00a0 El pie de foto de una de las noticias en ingles ven\u00eda a decir. <\/span><\/p>\n La adici\u00f3n de nutrientes al oc\u00e9ano causa un aumento en la producci\u00f3n de materia org\u00e1nica, como el fitoplancton. Cuando estos mueren, se hunden al fondo como<\/span> \u00ab<\/span>nieve marina<\/span><\/strong>\u00bb descomponi\u00e9ndose y consumiendo ox\u00edgeno en el proceso. Se cree que este es el principal responsable de la p\u00e9rdida de<\/span><\/strong><\/span> ox\u00ed<\/span><\/strong><\/strong>geno<\/span><\/strong> a gran escala en los antiguos oc\u00e9anos, lo que acarrear\u00eda extinciones masivas en el medio marino<\/span><\/strong>.<\/span><\/em><\/p>\n Al parecer, se trat\u00f3 de una cadena o cascada de eventos en los que tambi\u00e9n entran en juego vulcanismo y cambio clim\u00e1tico. Pero lo mismo puede ocurrir tras cualquier desastre natural de grandes dimensiones que<\/span><\/strong> da\u00f1ara la cobertura vegetal de la biosfera disparando el arrastre de una gran cantidad de sedimentos y nutrientes hacia el mar, desde la tierra emergida.\u00a0 Soslayar\u00e9 aqu\u00ed fechas, duraciones, etc., para terminar mentando que los autores defienden que lo mismo est\u00e1 ocurriendo actualmente\u00a0 como resultado del calentamiento clim\u00e1tico y la gran cantidad de nutrientes que desprenden las sociedades modernas<\/strong><\/span> con sus <\/span>fertilizantes, residuos<\/span><\/a>, etc. Y as\u00ed en las noticias en espa\u00f1ol castellano que dan cuenta de esta investigaci\u00f3n pueden leerse titulares de la siguiente y zafia guisa: <\/span>El cambio clim\u00e1tico, las aguas residuales y los fertilizantes podr\u00edan desencadenar una extinci\u00f3n masiva en los oc\u00e9anos<\/a>,<\/span><\/span> y est\u00e1 a\u00fan m\u00e1s exagerada si cabe: Los oc\u00e9anos, al borde de una anoxia de un mill\u00f3n de a\u00f1os<\/span><\/a>. \u00a1Amen!.<\/p>\n Yo no dudo de que tal hecho pudiera ocurrir bajo determinadas circunstancias. Ahora bien, ya estar\u00edamos mucho antes los humanos \u201cfuera de juego\u201d. Tampoco parece l\u00edcito extrapolar los c\u00e1lculos, siempre provisionales, de aqu\u00e9l remoto periodo para realizar predicciones futuras de tan largo plazo. Se me antoja un puro dislate. Empero en este caso, los propios autores parecen tener gran parte de la culpa, por proponer gratuitamente insanas ideas, que nacen de los inciertos paisajes del pasado, a las condiciones contempor\u00e1neas. Personalmente creo que de seguir as\u00ed el devenir de las publicaciones cient\u00edficas, habr\u00e1 que incluir en los curr\u00edculos de los j\u00f3venes investigadores cursos de publicidad \u00e9ticamente sostenible. Os dejo ya pues con \u00a0parte del material que he recopilado.\u00a0 \u00a0<\/span><\/p>\n Juan Jos\u00e9 Ib\u00e1\u00f1ez<\/strong><\/span><\/p>\n Contin\u00faa…….<\/em><\/span><\/span><\/p>\n \u00a0<\/span><\/p>\n Wikipedia: El Cenomaniense o Cenomaniano<\/span><\/a> es una divisi\u00f3n de la escala temporal geol\u00f3gica, la primera edad o piso del Cret\u00e1cico superior, segunda \u00e9poca del per\u00edodo Cret\u00e1cico. Esta edad se extiende de 100,5 hasta 93,9 millones de a\u00f1os atr\u00e1s<\/strong>, aproximadamente. La edad Cenomaniense sucede a la Albiense<\/strong>, del Cret\u00e1cico inferior, y precede a la Turoniense.<\/span><\/p>\n Arriaga Cavalieri, Maria Eugenia: \u00a0<\/span>Patrones de supervivencia y recuperaci\u00f3n de los macroforamin\u00edferos despu\u00e9s de la extinci\u00f3n en masa del l\u00edmite Cenomaniense-Turoniense<\/span><\/a>:<\/span><\/p>\n (\u2026) Durante la transici\u00f3n Cenomanience \u2013 Turoniense (CTB), la cual coincide con un episodio global de depositaci\u00f3n de sedimentos ricos en materia org\u00e1nica<\/strong> (Evento An\u00f3xico 2 o Evento Bonarelli<\/strong>), los macro-foramin\u00edferos que poblaban las plataformas carbonatadas fueron dram\u00e1ticamente afectados por el dr\u00e1stico cambio en las condiciones ambientales. Dicho cambio gener\u00f3 la octava mayor extinci\u00f3n de organismos marinos que se conoce,<\/strong> acabando con la comunidad de macro-foramin\u00edferos correspondiente al Ciclo de Maduraci\u00f3n Global del Cret\u00e1cico medio (GCMC)<\/strong>. <\/span>En esta tesis<\/strong> se discuten los patrones de recuperaci\u00f3n de los foramin\u00edferos luego de esta extinci\u00f3n. El trabajo ha sido realizado en dos paleobioprovincias contiguas: la del Tetis central (\u2026.) Surpirenaica Central).<\/span><\/p>\n la extinci\u00f3n en masa del l\u00edmite Cenomaniense-Turoniense<\/a>.<\/span><\/span><\/p>\n VENTO DEL L\u00cdMITE CENOMANIENSE\/TURONIENSE<\/span><\/a><\/p>\n El l\u00edmite C\/T datado en 93,9 Ma coincide con un evento de extinci\u00f3n relacionado con un suceso an\u00f3xico conocido como Oceanic Anoxic Event 2 (OAE2) o evento Bonarelli,<\/strong> que est\u00e1 muy bien representado en Italia, as\u00ed como en muchos cortes marinos distribuidos por todo el mundo. Se trata de unas facies arcillosas oscuras muy ricas en materia org\u00e1nica, que presentan disoluci\u00f3n de carbonatos. Este evento, ocurrido en el Cret\u00e1cico, dur\u00f3 aproximadamente medio mill\u00f3n de a\u00f1os afectando a muchos grupos de microorganismos, de invertebrados marinos y a algunos vertebrados como los reptiles lchthyosauria.<\/span><\/p>\n ASU graduate student leads study estimating oxygen loss in ancient global ocean<\/strong><\/a> A loss of oxygen in global ocean seawater <\/strong>94 million years <\/strong>ago led to a mass extinction of marine life that<\/strong> lasted for roughly half a million years. Scientists have found several potential explanations<\/strong> for how the loss of oxygen happened. These could include enhanced volcanic activity, increased nutrients reaching the ocean, rising sea levels, and warming sea and surface temperatures. But to point a finger at any one cause (or several of them) requires knowing<\/strong> how fast the oxygen loss happened<\/strong>.<\/p>\n A new technique, developed by Arizona State University graduate student Chad Ostrander with colleagues at Wood Hole Oceanographic Institution (WHOI) and Florida State University (FSU), has put a timetable on the oxygen loss associated with this major ocean extinction event, which is known to science as Oceanic Anoxic Event 2<\/strong>.<\/p>\n Their research was published August 9, 2017, in the journal Science Advances.<\/p>\n \u00abThe project began when I was an undergraduate Summer School Fellow at Woods Hole,\u00bb says Ostrander, a PhD student at ASU’s School of Earth and Space Exploration. His coauthors on the paper are Jeremy Owens at Florida State and Sune Nielsen at Woods Hole.<\/p>\n \u00abWe were able to track changes to the oxygen content of ancient seawater by measuring isotopes of thallium in ancient seafloor sediment<\/strong>s,\u00bb Ostrander explains. \u00abSince the oxygen in the rocks we measure wouldn’t really give any valuable information<\/strong>, we use thallium and other elements as stand-ins, or proxies.\u00bb<\/p>\n Sediments preserve the thallium isotope composition of seawater, which changes depending on the amount of oxygen in the deep ocean at the time they were deposited. The sediments pile up over time<\/strong>, with deeper levels corresponding to times further in the past.<\/p>\n The sediments the team studied were organic-rich black shales collected as core samples by deep ocean drillin<\/strong>g in 2003. The site was the Demerara Rise, a submarine plateau in the Atlantic Ocean off the coasts of Surinam and French Guyana<\/strong>.<\/p>\n \u00abWe dissolved the rocks in our lab,\u00bb explains Ostrander, \u00aband then chemically separated everything but thallium, the element we needed for analysis.\u00bb<\/p>\n Then using mass spectrometry, the team measured variations in thallium within sedimentary rocks as a proxy for changes in oxygen levels over tens of thousands of years.<\/p>\n Based on the analysis, the researchers suspect that up to half of the deep ocean had become oxygen-depleted during Oceanic Anoxic Event 2, and remained so for about half a million years before it recovered<\/strong>.<\/p>\n \u00abThe loss of oxygen took 43,000 years<\/strong> to occur, plus or minus about 11,000,\u00bb says Ostrander. \u00abCall it 50,000 years or less.\u00bb<\/p>\n The primary cause of Oceanic Anoxic Event 2 may have been increased nutrient delivery to the oceans<\/strong>, the researchers say. An increase in nutrients fuels the production of organic matter, and subsequent remineralization by bacteria feeding on it<\/strong>.<\/p>\n \u00abIt’s this remineralization that is specifically responsible for the oxygen loss, because these bacteria consume oxygen in order to oxidize the organic, or carbon-bearing, matter<\/strong>,\u00bb Ostrander says. \u00abWe see a similar scenario in the modern ocean, again due to increased nutrient delivery, but largely driven by fertilizers used in farming<\/strong>.\u00bb<\/p>\n In fact, he says, \u00abthe largest ‘dead zone’ observed in the Gulf of Mexico is occurring right now for this very reason<\/strong>.\u00bb<\/p>\n The researchers draw a distinct parallel between the rate of deoxygenation back then and modern trends in oceanic oxygen loss.<\/p>\n Says co-author Nielsen, \u00abOur results show that marine deoxygenation rates prior to the ancient event were likely occurring over tens of thousands of years, and are surprisingly similar to the two percent oxygen depletion trend we’re seeing induced by human-related activity over the last 50 years<\/strong>.\u00bb<\/p>\n He adds, \u00abWe don’t know if the ocean is headed toward another global anoxic event, but the trend is, of course, worrying.\u00bb<\/p>\n Ostrander says, \u00abAt this point, we are only just beginning to understand how oxygen levels in the ocean have changed in the past. But with our new tool, we’ve already learned that one of the most extreme climate events in the sedimentary record provides an uncomfortably reasonable<\/strong> analog for possible future ocean oxygen loss and subsequent ecological shifts.\u00bb<\/p>\n He adds, \u00abWe hope to use this information to gain a better look into the short-, medium- and long-term future for oxygen content in today’s oceans.\u00bb<\/p>\n Ancient ocean deoxygenation provides an urgent warning<\/strong><\/a> A 94-million-year-old climate change event that severely imperiled marine organisms<\/strong> may provide some unnerving insights into long-term trends in our modern oceans, according to a Florida State University researcher.<\/p>\n In a study published in the journal Science Advances<\/strong>, Assistant Professor of Geology Jeremy Owens traces a 50,000-year period of<\/strong> ocean deoxygenation preceding an ancient climate<\/strong> event that dramatically disturbed global ocean chemistry and led to the extinction of many marine organisms<\/strong>. He also draws parallels to similar rates of oxygen depletion observed in our contemporary oceans.<\/p>\n \u00abWe found that before this major shift in the climate, there was a stretch of oxygen depletion of about 50,000 years<\/strong>,\u00bb Owens said. \u00abThe rate of deoxygenation during that time is somewhat equivalent to the rate<\/strong> at which many scientists suggest we’re losing oxygen from our oceans today.\u00bb<\/p>\n Alongside scientists from Arizona State University and the Woods Hole Oceanographic Institution, Owens used a newly devised Thallium isotope analysis to examine organic-rich sediment from the Demerara Rise, an underwater plateau off the coasts of Suriname and French Guyana<\/strong>.<\/p>\n In these samples, Owens and his collaborators discovered evidence of rapid oxygen loss tens of thousands of years prior to the globally recognized climate event.<\/p>\n The best indicator for a significant climate disturbance<\/strong> like the one Owens and his colleagues investigated is the burial of large amounts of organic carbon<\/strong>. Owens said that the 50,000-year interval of deoxygenation preceding the climate event may help explain the relationship between buried organic carbon and major climatic shifts<\/strong>.<\/p>\n \u00abThe easiest way to bury organic carbon is for there to be a lack of oxygen<\/strong> because decreased oxygen slows down microbial respiration<\/strong>, and thus more primary producers sink down to the seafloor<\/strong>,\u00bb Owens said. \u00abThis oxygen depletion prior to the event makes a lot of sense as it sets the stage for widespread organic carbon burial – carbon that we now use for some of our fossil fuels.\u00bb<\/p>\n In the study, Owens found that the onset of the deoxygenation period corresponded with a marked rise in volcanic activity. As volcanism increased, carbon dioxide was pumped into a warming atmosphere and the oceans were suffused with an excess of nutrients, leading to a process of dense aquatic plant growth and rapid oxygen depletion called eutrophication<\/strong>.<\/p>\n The cascade of events that seems to have precipitated the 50,000-year deoxygenation period<\/strong> – carbon dioxide emissions, a warming atmosphere and eutrophication <\/strong>– is a familiar one to those studying modern fossil fuel combustion and climate change<\/strong>.<\/p>\n \u00abThe volcanism linked to deoxygenation in the past represents the same kind of process as we see today<\/strong> – we’re just dealing with different sources,\u00bb Owens said. \u00abIf the climate event in our study is analogous to modern events, we have to consider what that might mean for our oceans.\u00bb<\/p>\n While it’s unknown exactly how quickly the world’s oceans are deoxygenating, scientists estimate that they lose a small percentage every decade. On the scale of a human lifetime, this pace seems negligible. But on a geologic scale, this is happening quickly and could have major effects on the global ecosystem.<\/p>\n \u00abIt’s not a problem way off in the distance, and it’s not just carbon dioxide we should be worried about,\u00bb Owens said. \u00abThese processes are also having an impact on oxygen levels, and that’s a major issue for many organisms.\u00bb<\/p>\n Los oc\u00e9anos, al borde de una anoxia de un mill\u00f3n de a\u00f1os<\/span><\/a><\/p>\n Prohibido expl\u00edcitamente reproducir<\/strong><\/p>\n Los oc\u00e9anos, al borde de una anoxia de un mill\u00f3n de a\u00f1os CC0 PUBLIC DOMAIN Actualizado 12\/05\/2017 18:55:17 CET MADRID, 12 May. (EUROPA PRESS) – Dram\u00e1ticas ca\u00eddas en el ox\u00edgeno oce\u00e1nico, que causan extinciones masivas de la vida en el mar, llegan a su fin de forma natural, pero es algo que tarda alrededor de un mill\u00f3n de a …Leer mas: <\/span>http:\/\/www.europapress.es\/ciencia\/habitat-y-clima\/noticia-oceanos-borde-anoxia-millon-anos-20170512123759.html<\/span><\/a><\/p>\n (c) 2015 Europa Press. Est\u00e1 expresamente prohibida la redistribuci\u00f3n y la redifusi\u00f3n de este contenido sin su previo y expreso consentimiento<\/strong>.<\/span><\/p>\n
\n<\/strong><\/span>by Staff Writers
\nTempe AZ (SPX) Aug 16, 2017<\/p>\n
\n<\/strong><\/span>by Staff Writers
\nTallahassee FL (SPX) Aug 17, 2017<\/p>\n