Brief history of the Ocean Acidification through time.

Corals one of the most vulnerable creatures in the ocean. Photo Credit: Katharina Fabricius/Australian Institute of Marine Science

Corals one of the most vulnerable creatures in the ocean. Photo Credit: Katharina Fabricius/Australian Institute of Marine Science

At the end of the nineteenth century Svante Arrhenius and Thomas Chamberlain were among the few scientists that explored the relationship between carbon dioxide concentrations in the atmosphere and global warming. About one third of the carbon dioxide released by anthropogenic activity is absorbed by the oceans. But the CO2 uptake lowers the pH and alters the chemical balance of the oceans. This phenomenon is called ocean acidification, and is occurring at a rate faster than at any time in the last 300 million years (Gillings, 2014; Hönisch et al. 2012). Acidification affects the biogeochemical dynamics of calcium carbonate, organic carbon, nitrogen, and phosphorus in the ocean as well as the seawater chemical will directly impact in a wide range of marine organisms that build shells from calcium carbonate, like planktonic coccolithophores and pteropods and other molluscs,  echinoderms, corals, and coralline algae.

The geologic record of ocean acidification provide valuable insights into potential biotic impacts and time scales of recovery.  Rapid additions of carbon dioxide during extreme events in Earth history, including the end-Permian mass extinction (252 million years ago) and the Paleocene-Eocene Thermal Maximum (PETM, 56 million years ago) may have driven surface waters to undersaturation. But, there’s  no perfect analog for our present crisis, because we are living in an “ice house” that started 34 million years ago  with the growth of ice sheets on Antarctica, and this cases corresponded to events initiated during “hot house” (greenhouse) intervals of Earth history.

Coccolithophores exposed to differing levels of acidity. Adapted by Macmillan Publishers Ltd: Nature Publishing Group, Riebesell, U., et al., Nature 407, 2000.

Coccolithophores exposed to differing levels of acidity. Adapted by Macmillan Publishers Ltd: Nature Publishing Group, Riebesell, U., et al., Nature 407, 2000.

The end-Permian extinction is the most severe biotic crisis in the fossil record, with as much as 95% of the marine animal species and a similarly high proportion of terrestrial plants and animals going extinct . This great crisis ocurred about 252 million years ago (Ma) during an episode of global warming. The cause or causes of the Permian extinction remain a mystery but new data indicates that the extinction had a duration of 60,000 years and may be linked to massive volcanic eruptions from the Siberian Traps. The same study found evidence that 10,000 years before the die-off, the ocean experienced a pulse of light carbon that most likely led to a spike of carbon dioxide in the atmosphere. This could have led to ocean acidification, warmer water temperatures that effectively killed marine life.

The early Aptian Oceanic Anoxic Event (120 million years ago) was an interval of dramatic change in climate and ocean circulation. The cause of this event was the eruption of the Ontong Java Plateau in the western Pacific, wich led to a major increase in atmospheric pCO2 and ocean acidification. This event was characterized by the occurrence of organic-carbon-rich sediments on a global basis along with evidence for warming and dramatic change in nanoplankton assemblages. Several oceanic anoxic events (OAEs) are documented in Cretaceous strata in the Canadian Western Interior Sea.

major changes in plankton assembledge

The Paleocene-Eocene Thermal Maximum (PETM; 55.8 million years ago) was a short-lived (~ 200,000 years) global warming event. Temperatures increased by 5-9°C. It was marked by the largest deep-sea mass extinction among calcareous benthic foraminifera in the last 93 million years. Similarly, planktonic foraminifer communities at low and high latitudes show reductions in diversity. The PETM is also associated with dramatic changes among the calcareous plankton,characterized by the appearance of transient nanoplankton taxa of heavily calcified forms of Rhomboaster spp., Discoaster araneus, and D. anartios as well as Coccolithus bownii, a more delicate form

The current rate of the anthropogenic carbon input  is probably greater than during the PETM, causing a more severe decline in ocean pH and saturation state. Also the biotic consequences of the PETM were fairly minor, while the current rate of species extinction is already 100–1000 times higher than would be considered natural. This underlines the urgency for immediate action on global carbon emission reductions.

References:

Kump, L.R., T.J. Bralower, and A. Ridgwell. 2009. Ocean acidification in deep time. Oceanography 22(4):94–107, http://dx.doi.org/10.5670/oceanog.2009.100

Kroeker, K. J. et al. Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming. Glob. Change Biol. 19, 1884–1896 (2013).

Payne JL, Turchyn AV, Paytan A, Depaolo DJ, Lehrmann DJ, Yu M, Wei J, Calcium isotope constraints on the end-Permian mass extinction, Proc Natl Acad Sci U S A. 2010 May 11;107(19):8543-8. doi: 10.1073/pnas.0914065107. Epub 2010 Apr 26.

Zeebe RE and Zachos JC. 2013 Long-term legacy ofmassive carbon input to the Earth system: Anthropocene versus Eocene. Phil Trans R Soc A 371: 20120006.http://dx.doi.org/10.1098/rsta.2012.0006.

Daniel H. Rothman, Gregory P. Fournier, Katherine L. French, Eric J. Alm, Edward A. Boyle, Changqun Cao, and Roger E. Summons (2014) “Methanogenic burst in the end-Permian carbon cycle,” PNAS doi: 10.1073/pnas.1318106111

Michael R Gillings, Elizabeth L Hagan-Lawson, The cost of living in the Anthropocene,  Earth Perspectives 2014, DOI 10.1186/2194-6434-1-2

 

The sixth mass extinction: the human impact on biodiversity

800px-Ice_age_fauna_of_northern_Spain_-_Mauricio_Antón

Woolly mammoths in a late Pleistocene landscape in northern Spain (Author: Mauricio Antón) From Wikipedia Commons

At the beginning of the nineteenth century George Cuvier, the great French anatomist and paleontologist,  suggested that periodic “revolutions”, or catastrophes had befallen the Earth and wiped out a number of species, but under the influence of Lyell’s uniformitarianism, Cuvier’s ideas were rejected as “poor science”. One century after Cuvier definition of catastrophism, Chamberlain proposed that faunal major changes through time were under the control of epeirogenic movement of the continents and ocean basins. Despite Chamberlain’s article, the modern study of mass extinction did not begin until the middle of the twentieth century with a series of papers focused on the Permian extinction. One of the most popular of that time was “Revolutions in the history of life” written by Norman Newell in 1967.

Mass extinctions had shaped the global diversity of our planet several times during the geological ages. They are major patterns in macroevolution. Andrew Knoll defines them as perturbations of the biosphere which seem instantaneous when it is observed through the geological record.

The ‘‘Big Five’’ extinction events as identified by Raup and Sepkoski (1982)

The ‘‘Big Five’’ extinction events as identified by Raup and Sepkoski (1982)

In 1982, Jack Sepkoski and David M. Raup identified five mass extinctions. The first took place at the end of the Ordovician period, about 450 million years ago.  Now, according to the current rates of extinction, we are in the midst of  the so called “Sixth Mass Extinction”.

Mass extinctions are probably due to a set of different possible causes like basaltic super-eruptions, impacts of asteroids, global climate changes, or continental drift. But now, a group of scientists like Edward O. Wilson and Niles Eldredge identified post-industrial humans as the driving force behind the current and on-going mass extinction (Braje, 2013).

The human arrival was a “key component” in the extinction of the megafauna during the late Quaternary. In North America, approximately 34 genera (72%) of large mammals went extinct between 13,000 and 10,500 years ago, including mammoths, mastodons, giant ground sloths, horses, tapirs, camels, bears, saber-tooth cats, and a variety of other animals. South America lost an even larger number and percentage, with 50 megafauna genera (83%) becoming extinct at about the same time.

 

Richard Owen stands next to the largest of all moa, Dinornis maximus (now D. novaezealandiae). From Wikimedia Commons.

Richard Owen stands next to the largest of all moa, Dinornis maximus (now D. novaezealandiae). From Wikimedia Commons.

Other extinctions on island ecosystems around the world are result from direct human hunting, anthropogenic burning and landscape clearing, and the translocation of new plants and animals. One of the most famous and well-documented of these extinctions come from Madagascar. Pygmy hippos, giant tortoises, and large lemurs went extinct due to human hunting or habitat disturbance. A very interesting study by Burney et al. (2003) tracked the decline of coprophilous Sporormiella fungus spores in sediments due to reduced megafaunal densities after the human arrival on the island.  Another well documented case is the Moa extinction in New Zealand. Recent radiocarbon dating and population modeling suggests that their disappearance occurred within 100 years of first human arrival. A large number of  landbirds across Oceania suffered a similar fate beginning about 3500 years ago.

The anthropogenic effects increasingly took precedence over natural climate change as the driving forces behind plant and animal extinctions with the advent of agriculture and the domestication of animals.

The Panamanian golden frog (Atelopus zeteki). Credit: Brian Gratwicke. From Wikimedia Commons

The Panamanian golden frog (Atelopus zeteki). Credit: Brian Gratwicke. From Wikimedia Commons

Amphibians offer an important signal to the health of biodiversity; when they are stressed and struggling, biodiversity may be under pressure.   Today, they are the world’s most endangered class of animal, while corals have had a dramatic increase in risk of extinction in recent years. Some biologist predict that the sixth extinction  may result in a 50% loss of the plants and animals on our planet by AD 2100, which would cause not only the collapse of ecosystems but also the loss of food economies, and medicinal resources.

The acceleration of extinctions over the past 50,000 years, in which humans have played an increasingly important role, has left a number of hard questions about how the Anthropocene should be defined and whether or not extinctions should contribute to this definition (Erlandson, 2013)

 

References:

T.J., Erlandson, J.M., Human acceleration of animal and plant extinctions: A Late Pleistocene, Holocene, and Anthropocene continuum. Anthropocene (2013)

A.D. Barnosky, N. Matzke, S. Tomiya, G.O.U. Wogan, B. Swartz, T.B. Quental, C. Marshall, J.L. McGuire, E.L. Lindsey, K.C. Maguire, B. Mersey, E.A. Ferrer, Has the earth’s sixth mass extinction already arrived?, Nature, 471 (2011), pp. 51–57.

Mayhew, Peter J.; Gareth B. Jenkins, Timothy G. Benton (January 7, 2008). “A long-term association between global temperature and biodiversity, origination and extinction in the fossil record”. Proceedings of the Royal Society B: Biological Sciences 275 (1630): 47–53.

D.A. Burney, L.P. Burney, L.R. Godfrey, W.L. Jungers, S.M. Goodman, H.T. Wright, A.J.T. Jull, A chronology for late prehistoric Madagascar, J. Hum. Evol., 47 (2004), pp. 25–63

The Salagrama stones and the early history of ammonite studies.

Ammonites  found near Yeovil in Somerset. From Natural History Museum database. © The Natural History Museum, London

Ammonites found near Yeovil in Somerset. From Natural History Museum database. © The Natural History Museum, London

Ammonites are the common name given to the subclass Ammonoidea, an extinct order of cephalopod. The first occurrence of ammonites is from the Devonian around 400 million years ago. The last surviving lineages disappeared, along with the dinosaurs, 65 million years ago in the Cretaceous–Paleogene extinction event.

Since antiquity, ammonites has been associated with myths, legends, religion and even necromancy. They were known as “Cormu Ammonis”, “Corni de Ammone” or “Cornamone” because their shapes resemble the tightly coiled rams horns used to represent the Egyptian god Ammon. Pliny the Elder (AD 23 – August 25, AD 79) referred them in his monumental work Naturalis Historia. He wrote: “The Hammonis cornu is among the holiest gems of Ethiopia, it is golden in colour and shows the shape of a rams horn; one assures that it causes fortune-telling dreams”. This could be explained because pyritised ammonites have a sparkling, golden appearance.

The salagramas are ammonites worshipped as divine symbols of Vishnu—the four-armed God, Sustainer of the Universe who holds a disc or wheel (chakra) in one of his hands.  In China, were described as horn stones ( jiao-shih) and they being used as an ancient remedy. Japanese referred them as chrysanthemum stones (kiku-ishi) and Buddhists interpreted them as a symbol of enlightenment.

Jeletzkytes spedeni, a fossil ammonite from USA. From Wikimedia Commons.

Jeletzkytes spedeni, a fossil ammonite from USA. From Wikimedia Commons.

They have been interpreted as petrified venomous snake (“ophites”) often called “serpentstones”. In medieval England, they were considered evidence for the actions of saints such Saint Patrick or St. Hilda of Whitby. According to tradition, these fossil Ammonites were  serpents that infested the region of Whitby,  before the coming of St. Hilda. This is cited in Sir Walter Scott’s Marmion:

“… Of thousand snakes, each one

Was changed into a coil of stone,

When holy Hilda prayed;

Themselves, within their holy bound,

Their stony folds had often found.”

Ammonite fossil illustrations drawn by Robert Hooke (‘Discourse on Earthquakes’ from 1703).

Ammonite fossil illustrations drawn by Robert Hooke (‘Discourse on Earthquakes’ from 1703).

Georgius Agricola, often named as “the father of mineralogy” and author of De Re Metallica, a work based on Pliny’s work Historia Naturalis, also referred them as Ammonis Cornu.  Conrad Gessner include some ammonite’s illustration is his work De rerum fossilium (1565). But even toward the end of 17th century the ammonite organic nature was still under debate. Robert Hooke was fascinated by the logarithmic coil of ammonite shells and their regularly arranged septa. He reached the conclusion that ammonites are not only of organic origin but also widely resemble Nautilus. A landmark in ammonite research was the classification scheme given by Johann Jacob Scheuchzer in 1716.

The modern form of the word ammonite was coined by the French zoologist Jean Guillaume Bruguière (c.1750-1798) in 1790, but only in 1884 the subclass Ammonoidea was formalized in zoological taxonomy.

References:

Marco Romano, From petrified snakes, through giant ‘foraminifers’, to extinct cephalopods: the early history of ammonite studies in the Italian peninsula, Historical Biology 2014, http://dx.doi.org/10.1080/08912963.2013.879866

Van der Geer AAE, Dermitzakis MD, De Vos J. Fossil Folklore from India: The Siwalik Hills and the Mahâbhârata, Folkore 119: 71-92. London: The Folklore Society (2008)

The Chicxulub impact and the acid rain.

Chicxulub impact site (painting by Donald E. Davis) From Wikimedia Commons

Chicxulub impact site (painting by Donald E. Davis) From Wikimedia Commons

About thirty years ago, the discovery of anomalously high abundance of iridium and other platinum group elements in the Cretaceous/Palaeogene (K-Pg) boundary led to the hypothesis that a 10 km asteroid collided with the Earth and caused one of the most devastating events in the history of life. The impact created the 180-kilometre wide Chicxulub crater causing widespread tsunamis along the coastal zones of the surrounding oceans and released an estimated energy equivalent of 100 teratons of TNT and produced high concentrations of dust, soot, and sulfate aerosols in the atmosphere. The vapour produced by the impact  could have led to global acid rain and a dramatic acidification of marine surface waters. Calcareous nanoplankton (primarily the coccolithophores) and planktonic foraminifera had the highest extinction rates among the marine plankton.

Radar topography reveals the 180 km-wide (112 mi) ring of the Chicxulub Crater. From Wikimedia Commons

Radar topography reveals the 180 km-wide (112 mi) ring of the Chicxulub Crater. From Wikimedia Commons

But the exact mechanism that lead to the demise of the 75%  of all life on Earth including the non-avian dinosaurs still remain debated. To test the hypothesis that acid rain could have caused the extinction patterns observed, Sohsuke Ohno and colleagues at the Chiba Institute of Technology in Japan mounted natural anhydrite – the bedrock of the Chicxulub crater is largely anhydrite -   in a vacuum chamber with a chemically inert, high density tantalum metal plate backed with a plastic ablator a short distance from it.  The team used lasers to fire impactors into anhydrite test samples at velocities of 13 to 25 kilometres per second, very similar to the speeds expected in an asteroid impact. 

The mass spectrometer analysis, showed  there was more sulphur trioxide molecules than sulphur dioxide. Sulphur trioxide reacts quickly with atmospheric water vapour and form sulphuric acid aerosols. These sprays adhere to particles heavier silicates ejected into the atmosphere by the impact, returning to the surface much faster than previously thought. These results could also explain the so called fern spike right after the impact event, because ferns are one of the most tolerant plants for dealing with those conditions.

References:

Sohsuke Ohno, Toshihiko Kadono, Kosuke Kurosawa, Taiga Hamura, Tatsuhiro Sakaiya, Keisuke Shigemori, Yoichiro Hironaka, Takayoshi Sano, Takeshi Watari, Kazuto Otani, Takafumi Matsui  and Seiji Sugita, Production of sulphate-rich vapour during the Chicxulub impact and implications for ocean acidification, Nature Geoscience (2014) doi:10.1038/ngeo2095

A brief introduction about the origin of Eukaryotes.

Sonderia sp. (a ciliate that preys upon various algae, diatoms, and cyanobacteria). Photo credit: Diana Lipscomb, George Washington University, Washington, D.C.

Sonderia sp. (a ciliate that preys upon various algae, diatoms, and cyanobacteria). Photo credit: Diana Lipscomb, George Washington University, Washington, D.C.

In 1883, the first person to suggested the endosymbiotic nature of eukaryotic cells was the German botanist Andreas Schimper, and in 1926 Russian botanist Konstantin Mereschkowsky and American biologist Ivan Wallin, postulated the idea that symbiosis is the main driving force of evolution in their book “Symbiogenesis and the Origin of Species”. In 1981, American Biologist Lynn Margulis published ”Symbiosis in Cell Evolution” and proposed that the complexity of the eukaryotic cell was assembled over a long time period by symbiotic associations between different kinds of prokaryotes and an amitochondriate protozoa host.

The mosaicism of the eukaryotic genome is challenging. Bacteria, Archaea, and Eukarya share common ancestry but they have very distinctive features. Eukarya are similar to Archaea for some systems like the replication, transcription,and translation apparatuses and to Bacteria for others like metabolism and membrane chemistry (Rochette, 2014), so the different hypotheses are associated with different phylogenomic prediction.

(a) The Serial Endosymbiotic Theory and (b) The Neomuran Hypothesis (from Armstrong 2005)

(a) The Serial Endosymbiotic Theory and (b) The Neomuran Hypothesis (from Armstrong 2005)

All these hypotheses can be classified into three main classes: hypotheses involving endosymbiosis, which argue that components of the eukaryotic cell arose by engulfment of prokaryotic organisms,  hypotheses for autogenous (‘self-birth’) pathways for eukaryotic cell components, and a “ternary” hypotheses suggest that the organism that engulfed the ancestor of mitochondria was itself a chimera of two prokaryotes.
The “hydrogen hypothesis” (Martin and Müller 1998) involves endosymbiosis and implies that ancestral eukaryotic genes are derived from the alphaproteobacterial ancestor of mitochondria and from the methanogenic euryarchaeon that hosted it. The Neomura hypothesis (Cavalier-Smith 2010b) is among the autogenous hypotheses and assumes that Eukarya are the sister group of all Archaea. Finally, a popular ternary hypothesis is the “endokaryotic” hypotheses in which the nucleus derives from an archaeon while the cytoplasm derives from a bacterium (Lake and Rivera 1994).
A recent analysis establishes that there is no phylogenomic support in favor of ternary hypotheses and support that Eukarya branch close to Archaea or basally within them and that some early-mitochondria hypotheses are compatible with current genomic data under certain assumptions (Rochette, 2014).

Cosmarium sp. (desmid) near a Sphagnum sp. leaf (Photo Credit: Marek Mis)

Cosmarium sp. (desmid) near a Sphagnum sp. leaf (Photo Credit: Marek Mis)

It’s possible that the last eukaryotic common ancestor (LECA) had a modern nucleus (Mans et al. 2004), a cytoskeleton based on microtubules and actin (Yutin et al. 2009; Hammesfahr and Kollmar 2012), a complete vesicle and membrane-trafficking system allowing for endocytosis (Dacks et al. 2009; Yutin et al. 2009; De Craene et al. 2012), mitochondria (which are derived alphaproteobacteria; Embley and Martin 2006; Gabaldón and Huynen 2007), a modern cell cycle (Eme et al. 2011), and a sexual cycle (Ramesh et al. 2005)

References:

Nicolas C. Rochette, Céline Brochier-Armanet, and Manolo Gouy, Phylogenomic test of the hypotheses for the evolutionary origin of eukaryotes, Mol. Biol. Evol. 2014 : mst272

Yonas I. Tekle,  Laura Wegener Parfrey, Laura A. Katz, Molecular Data Are Transforming Hypotheses on the Origin and Diversification of Eukaryotes, BioScience(2009),59(6):471 http://dx.doi.org/10.1525/bio.2009.59.6.5

The Rise of Oxygen and the early animals.

image_1413_1e-palaeosol

Iron formation from the Pongola Supergroup, South Africa. Credit: Nic Beukes/Univ. of Johannesburg.

Earth is the only planet in our Solar System with high concentrations of gaseous diatomic oxygen. Simultaneously, this unique feature of Earth’s atmosphere has allowed the presence of an ozone layer that absorbed UV radiations. But the oxygen content of Earth’s atmosphere has varied greatly through time. For about the first 2 billion years of Earth’s history, the atmospheric oxygen concentration was exceptionally low.

It’s widely assumed that about 2.3 billion years ago, the level of oxygen increased dramatically in a process called the Great Oxidation Event (GOE). This rise in oxygen level occurred during an episode of major glaciation known as the Huronian glaciation. The progressive oxygenation of the atmosphere and oceans was sustained by an event of high organic carbon burial, called the Lomagundi Event, which lasted well over 100 million years, and represents the largest positive carbon-isotope excursion in Earth history (Canfield, 2013). This early oxygen primary production  was exclusively conducted by prokaryotes, specifically by cyanobacteria.

Precambrian stromatolites in the Siyeh Formation, Glacier National Park. From Wikimedia Commons.

Precambrian stromatolites in the Siyeh Formation, Glacier National Park. From Wikimedia Commons.

However, new geochemical  evidence suggested that there were appreciable levels of atmospheric oxygen about 3 billion years ago, more than 600 million years before the Great Oxidation Event, indicating a greater antiquity for oxygen producing photosynthesis and aerobic life.

After the GOE, oxygen levels rose again and then fell in the atmosphere and remained at extremely low levels for more than a billion years. This was probably due to a particular combination of  biogeochemical feedbacks that spawned an oxygen-lean deep ocean (Lyons, 2014). The general oxygenation of the oceans began around 750-550 million years ago. This recovery  of oxygen levels led to a significant increase in trace metals in the ocean and possibly triggered the ‘Cambrian explosion of life’ (Large, 2014).

Halichondria panicea, a temperate marine demosponge (Photo: Daniel Mills)

Halichondria panicea, a temperate marine demosponge (Photo: Daniel Mills)

But early animals, in general, may have had relatively low oxygen requirements. According to new findings, a sea sponge – the living animal that most resembles the earliest animals on Earth – can live and grow even at atmospheric oxygen levels that are 0.5 percent of today’s levels, which challenges the notion that low oxygen levels were the limiting factor for animal evolution. The study also suggest that the evolution of sophisticated gene regulatory networks, may have controlled the timing of animal origins more so than environmental parameters  (Mills, 2014)

References:

Donald E. Canfield, Lauriss Ngombi-Pemba, Emma U. Hammarlund, Stefan Bengtson, Marc Chaussidon, François Gauthier-Lafaye, Alain Meunier, Armelle Riboulleau, Claire Rollion-Bard, Olivier Rouxel, Dan Asael, Anne-Catherine Pierson-Wickmann, and Abderrazak El Albani,  Oxygen dynamics in the aftermath of the Great Oxidation of Earth’s atmosphere PNAS 2013 110 (42) 16736-16741; published ahead of print September 30, 2013, doi:10.1073/pnas.1315570110.

Daniel B. Mills, Lewis M. Ward, CarriAyne Jones, Brittany Sweeten, Michael Forth, Alexander H. Treusch, and Donald E. Canfield, Oxygen requirements of the earliest animals, PNAS 2014 ; published ahead of print February 18, 2014, doi:10.1073/pnas.1400547111

Timothy W. Lyons, Christopher T. Reinhard, Noah J. Planavsky. The rise of oxygen in Earth’s early ocean and atmosphere. Nature, 2014; 506 (7488): 307 DOI: 10.1038/nature13068

Diatoms and Climate Change.

Diatoms living between crystals of annual sea ice in McMurdo Sound, Antarctica. From Wikimedia Commons.

Diatoms living between crystals of annual sea ice in McMurdo Sound, Antarctica. From Wikimedia Commons.

Diatoms are unicellular algae with golden-brown photosynthetic pigments with a fossil record that extends back to Early Jurassic. The most distinctive feature of diatoms is their siliceous skeleton known as frustule that comprise two valves. The formation of this opaline frustule is linked  in modern oceans with the biogeochemical cycles of silicon and carbon.

Because their abundance and sensitivity to different parameters,  diatoms play a key role in Paleoceanography , particularly for evidence of climatic cooling and changing sedimentation rates in the Arctic and Antarctic oceans and to estimate sea surface temperature. Also, diatom diversity can be used as a proxy for the influence of diatoms on marine export productivity and the carbon cycle.

Diatoms are thought to have diversified over the Cenozoic. Early Cenozoic oceans were relatively warm, but in the early to mid Eocene, ocean surface temperatures began to cool, and polar regions and tropical regions began to be more strongly differentiated. It was suggested that Late Eocene diatom proliferation likely occurred in response to subsidence of Southern Ocean land bridges and the concurrent development of circum-Antarctic upwelling.

Actinocyclus ingens Rattray and Thalassiosira convexa (SEM, Neogene diatoms from the Southern Ocean, ODP)

Actinocyclus ingens Rattray and Thalassiosira convexa (SEM, Neogene diatoms from the Southern Ocean, ODP)

Peak species diversity in marine planktonic diatoms occurred at the Eocene–Oligocene boundary followed by a pronounced decline, from which they have not recovered (Rabosky 2009).  During the early late Miocene, when temperatures and pCO2 were only moderately higher than today, diatoms lost about 20% of its diversity. Warmer oceans are linked with lower diatom diversity, suggesting that future warmer oceans due to anthropogenic warming may result in lower diatom diversity (Lazarus, 2014).

During the last 15 million years, diatom diversity is correlated with global carbon isotope record and with the past atmospheric pCO2, suggesting that diatoms have played a very important role in the evolution of mid-Miocene to Recent climate for their prominent role in the carbon pump.

References:

Armstrong, H. A., Brasier, M. D., 2005. Microfossils (2nd Ed). Blackwell, Oxford.

Lazarus D, Barron J, Renaudie J, Diver P, Türke A (2014) Cenozoic Planktonic Marine Diatom Diversity and Correlation to Climate Change. PLoS ONE 9(1):e84857. doi:10.1371/journal.pone.0084857

Egan KE, Rickaby REM, Hendry KR, Halliday AN (2013) Opening the gateways for diatoms primes Earth for Antarctic glaciation. Earth and Planetary Science Letters 375: 34–43. doi: 10.1016/j.epsl.2013.04.030

Women in the Golden Age of Geology in Britain.

A sketch of a Plesiosaur by Mary Anning, 1824.

A sketch of a Plesiosaur by Mary Anning, 1824. From original manuscripts held at the Natural History Museum, London. © The Natural History Museum, London

The nineteen century was the “golden age” of Geology. The Industrial Revolution ushered a period of canal digging and major quarrying operations for building stone. These activities exposed sedimentary strata and fossils. So, the concept of an ancient Earth became part of the public understanding and Literature influenced the pervasiveness of geological thinking. The study of the Earth became central to the economic and cultural life of the nation and in 1807, the Geological Society of London is founded with the purpose of making that geologists become familiar with each other, adopting one nomenclature and  facilitating the communications of new facts.

The most popular aspect of geology was  the collecting of fossils and minerals and the nineteenth-century geology, often perceived as the sport of gentlemen,was in fact, “reliant on all classes” (Buckland, 2013). Women were free to take part in collecting fossils and mineral specimens, and they were allowed to attend lectures but they were barred from membership in scientific societies. It was common for male scientists to have women assistants, but most of them went unacknowledged and become lost to history (Davis, 2009). However, some women found the way to cross that line and make a name in Geology.

Mary Elizabeth (née Horner) Lyell, (1808–1873), wife of Sir Charles Lyell, by Horatio Nelson King © National Portrait Gallery, London, and Mary Ann (née Woodhouse) Mantell (1795–1869), wife of Dr. Gideon Mantell, © 2014 The Natural History Museum.

Mary Elizabeth (née Horner) Lyell, (1808–1873), wife of Sir Charles Lyell, by Horatio Nelson King © National Portrait Gallery, London, and Mary Ann (née Woodhouse) Mantell (1795–1869), wife of Dr. Gideon Mantell, © 2014 The Natural History Museum, London.

The early female scientists belonged to wealthy families or they benefited from their associations. In the first group we could find Etheldred Benett of Wilshire (1776–1845), she described the stratigraphic and geographic distribution of fossils of Wiltshire. Although she was not formally published, Benett wrote several manuscripts, which are now in the collections of the Geological Society of London.

Barbara Rawdon (née Yelverton) Hastings (1810–1858), 20th Baroness Grey de Ruthyn and Marchioness of Hastings was known as a fossil collector and a “lady-geologist” . She is also well known for the “Hastings Collection,” consisting of several thousand fossil specimens from England and Europe. She also studied the stratigraphy of England and published her findings in “Description géologique des falaises d’Hordle, et sur la côte de Hampshire, en Angleterre” (Hastings, 1851–52) and “On the tertiary beds of Hordwell, Hampshire” (Hastings, 1853).

The Philpot sisters (Margaret, ?–1845; Mary, 1773?–1838; Elizabeth, 1780–1857) were also well know for their fossil collection and their friendship with Mary Anning. They lived in Lymes Regis and amassed an important collection of fossils from the Jurassic. Elizabeth maintained correspondences with William Buckland, William Conybeare, Henry De la Beche, Richard Owen, James Sowery and Louis Agassiz.

Skull of Crocodilus hastingsiae named by Sir Richard Owen, in honor to Barbara Hastings. Image from Wikimedia Commons.

Skull of Crocodilus hastingsiae named by Sir Richard Owen, in honor to Barbara Hastings. Image from Wikimedia Commons.

In the other group we could find those women who worked with their husbands. The most prominent of these women were Mary (née Moreland) Buckland (1797–1857), wife of Rev. William Buckland; Mary Ann (née Woodhouse) Mantell (1795–1869), wife of Dr. Gideon Mantell; Charlotte (née Hugonin) Murchison (1789–1869) wife of Sir Roderick Murchison; and Mary Elizabeth (née Horner) Lyell (1808–1873), wife of Sir Charles Lyell (Davis, 2009).

Mary Morland (1797–1857) illustrated some of George Cuvier’s work before she became Mrs William Buckland. She made models of fossils for the Oxford museum and repaired broken fossils. She assisted her husband by taking notes of his observations and illustrating his work. After the death of her husband, she continued working on marine zoophytes.

Charlotte Murchinson (1789–1869) was a strong influence for her husband and introduced him in the world of geology. She accompanied him on excursions and spent time sketching the  landscape and outcrops and collecting Jurassic fossil specimens from the beaches.

Mary Mantell (1795–1869) discovered the teeth of Iguanodon, which led to her husband’s publication of an important paper announcing the discovery of a new giant reptile (Creese and Creese, 1994). She also made the illustration of Mantell’s work: “Fossils of the South Downs: or Illustrations of the Geology of Sussex”. Mary Mantell left her husband in 1839 and the children remained with their father as was customary.

Mary Lyell (1808–1873) was daughter of the geologist Leonard Horner. She read both French and German fluently and translated scientific papers for her husband and managed his correspondence. She later specialized in conchology and regularly attended meetings of the London Geological Society.

Megalosaurus' jaw and teeth drawn by Mary Buckland. © Paul D Stewart / Science Photo Library

Megalosaurus’ jaw and teeth drawn by Mary Buckland. © Paul D Stewart / Science Photo Library

Mary Anning (1799-1847), was an special case. Despite her lower social condition and the fact that she was single, Mary became the most famous woman paleontologist of her time. She found the first specimens of what would later be recognized as Ichthyosaurus, the first complete Plesiosaurus, the first pterosaur skeleton outside Germany and suggested that the “Bezoar stones” were fossilized feces.

Fighting in their own way against the difficulties, women had contributed significantly to the development of geology and paleontology. Fortunately, geoscientists and historians are rescuing these woman from oblivion.

References:

BUREK, C. V. & HIGGS, B. (eds) The Role of Women in the History of Geology. Geological Society, London, Special Publications, 281, 1–8. DOI: 10.1144/SP281.1.

Davis, Larry E. (2009) “Mary Anning of Lyme Regis: 19th Century Pioneer in British Palaeontology,” Headwaters: The Faculty Journal of the College of Saint Benedict and Saint John’s University: Vol. 26, 96-126.

Buckland, Adelene: Novel Science : Fiction and the Invention of Nineteenth-Century Geology, University of Chicago Press, 2013.

A Brief Introduction to Paleoecology.

Duria Antiquior famous watercolor by the geologist Henry de la Beche based on fossils found by Mary Anning. From Wikimedia Commons.

Duria Antiquior famous watercolor by the geologist Henry de la Beche based on fossils found by Mary Anning. From Wikimedia Commons.

Paleocology is a multidisciplinary science. It involves the reconstruction of past environments from geological and fossil  evidence. A more exhaustive definition was given by Valentí Rull in 2010: “the branch of ecology that studies the past of ecological systems and their trends in time using fossils and other proxies”. Paleoecology can be used to investigate (1) the rates of speciation and extinction, (2) biome shifts and ecosystem development and (3) adaptation, migration, and population change (Seppä, 2009).

Charles Lyell (1797–1875) and Roman Fedorovich Gekker (1900-1991)

Charles Lyell (1797–1875) and Roman Fedorovich Gekker (1900-1991)

The major philosophical concepts in paleoecology are uniformitarianism, analogy, and parsimony. The concept of uniformitarianism was created by James Hutton (1726–97) and  Charles Lyell (1797–1875). It can be summarized as ‘the present is the key to the past’ and is the basic principle of paleoecology. The concept of analogy involves the application of modern organismic features to ancient organisms, and of course parsimony is a central rule for any scientific inquiry. In 1933, the Russian paleontologist Roman Gekker published the first book dedicated to paleoecology: “Manual to Paleoecology”, based in his lectures about the Devonian Period. In this book he established the main objectives of Paleoecology. Later, in 1954, he wrote “Directions for Research in Paleoecology” and in 1957, he published “Introduction to Paleoecology”.

Scanning electron microscope image of different types of pollen grains. Image from Wikipedia.

Scanning electron microscope image of different types of pollen grains. Image from Wikipedia.

There are two major types of paleoecology: Quaternary paleoecology, concerned with the last 2.6 million years of Earth’s history, and Deep-time paleoecology, based on fossils from pre-Quaternary sediments over a wide range of timescales (Birks, 2013). In the last four decades, quantitative methods for reconstructing environmental variables have been developed from a range of biological proxies such as pollen, plant macrofossils, insects (chironomids, coleopterans), molluscs, ostracods, diatoms, chrysophycean cysts, testate amoebae, and cladocerans preserved in lake sediments and peat profiles, or dinoflagellate cysts, diatoms, pollen, foraminifera, coccolithophores, and radiolarians preserved in marine sediment records.

Lago Sarmiento in Southern Patagonia. Sediment cores recovered from lakes like this, help to reconstruct environmental changes. Photo credit: R. Dunbar.

Lago Sarmiento in Southern Patagonia. Sediment cores recovered from lakes like this, help to reconstruct environmental changes. Photo credit: R. Dunbar.

The dominant technique in Quaternary terrestrial paleoecology is the pollen analysis. Pollen analysis involves the quantitative examination of spores and pollen at successive horizons through a core, particularly in bog, marsh, lake or delta sediments (Armstrong, 2005). This method was created by Lennart von Post (1884–1950), a Swedish geologist and presented at the 16th Scandinavian meeting of natural scientists in Oslo. Since the 1980s, many fossil pollen data sets were developed specifically to reconstruct past climate change.

Reference:

Seddon, A. W. R., Mackay, A. W., Baker, A. G., Birks, H. J. B., Breman, E., Buck, C. E., Ellis, E. C., Froyd, C. A., Gill, J. L., Gillson, L., Johnson, E. A., Jones, V. J., Juggins, S., Macias-Fauria, M., Mills, K., Morris, J. L., Nogués-Bravo, D., Punyasena, S. W., Roland, T. P., Tanentzap, A. J., Willis, K. J., Aberhan, M., van Asperen, E. N., Austin, W. E. N., Battarbee, R. W., Bhagwat, S., Belanger, C. L., Bennett, K. D., Birks, H. H., Bronk Ramsey, C., Brooks, S. J., de Bruyn, M., Butler, P. G., Chambers, F. M., Clarke, S. J., Davies, A. L., Dearing, J. A., Ezard, T. H. G., Feurdean, A., Flower, R. J., Gell, P., Hausmann, S., Hogan, E. J., Hopkins, M. J., Jeffers, E. S., Korhola, A. A., Marchant, R., Kiefer, T., Lamentowicz, M., Larocque-Tobler, I., López-Merino, L., Liow, L. H., McGowan, S., Miller, J. H., Montoya, E., Morton, O., Nogué, S., Onoufriou, C., Boush, L. P., Rodriguez-Sanchez, F., Rose, N. L., Sayer, C. D., Shaw, H. E., Payne, R., Simpson, G., Sohar, K., Whitehouse, N. J., Williams, J. W., Witkowski, A. (2014), Looking forward through the past: identification of 50 priority research questions in palaeoecology. Journal of Ecology, 102: 256–267. doi: 10.1111/1365-2745.12195

Seppä, H. 2009. Palaeoecology. eLS DOI: 10.1002/9780470015902.a0003232

Walker, Mike J. C., and John J. Lowe. 2007. Quaternary science 2007: A 50-year retrospective.Journal of the Geological Society 164.6: 1073–1092. DOI: 10.1144/0016-76492006-195

Wenupteryx uzi, a Jurassic pterosaur from Patagonia.

Wenupteryx uzi, photograph of the slab. From Codorniu-Gasparini 2013.

Wenupteryx uzi, photograph of the slab. From Codorniu-Gasparini 2013.

By the Mid-Jurassic, Gondwana, the southern margen of supercontinent Pangea started to break up in different blocks: Antarctica, Madagascar, India, and Australia in the east, and Africa and South America in the west. During this period pterosaurs had a worldwide distribution, but their known record is markedly biased toward the northern hemisphere. For example, the ‘Solnhofen Limestone’ beds in Germany yielded important pterosaur specimens, mostly members of the genera Pterodactylusand Rhamphorhynchus. Other famous fossil-bearing deposits are from North America, and from the Tiaojishan Formation in China.

In contrast, the fossil remains of pterosaurs from Jurassic sediments are very scarce in the southern hemisphere. The oldest record comes from the Middle Jurassic of Patagonia, in the Cañadon Asfalto Formation, which is mainly composed of lacustrine deposits.

Wenupteryx uzi, reconstruction from Codorniú 2013.

Wenupteryx uzi, reconstruction from Codorniú 2013.

The most complete pterosaur known so far is Wenupteryx uzi described by Laura Codorniu and Zulma Gasparini. In the Mapuche Languaje, Wenu means “sky” and uzi means “fast”.

Wenupteryx uzi, is a small pterosaur . The bones recovered so far are a nearly complete post-cranial skeleton,which includes: some cervical and dorsal vertebrae; a few thoracic ribs, a proximal right-wing (humerus, ulna and radius, right metacarpal IV, pteroid), a more complete left-wing and hindlimb bones. This pterosaurs has a wingspan approaching 1-10 m.
Based on the presence of some characters, like the depressed neural arch of the mid-series cervicals, with a low neural spine and elongate mid-series cervicals. Wenupteryx uzi is closely related to the Euctenochasmatia, which matches with Unwin’s phylogeny (Unwin, 2003).


References:

Laura Codorniú and Zulma Gasparini (2013). «The Late Jurassic pterosaurs from northern Patagonia, Argentina». Earth and Environmental Science Transactions of the Royal Society of Edinburgh 103 (3–4):  pp. 399–408. doi:10.1017/S1755691013000388.