Forgotten women of paleontology: Irene Crespin

Irene Crespin (1896-1980)

Irene Crespin was born on November 12, 1896, in Kew, Victoria, Australia. In her memories, she wrote that her interest in Palaeontology began early in her life, when she was one of the first students to attend the Mansfield High School in northeastern Victoria. The head master of for a short period was the eminent Australian geologist Charles Fenner.

In 1919, she graduated with a B.A. from the University of Melbourne. In 1927 she joined the Commonwealth Government as Assistant Palaeontologist to Frederick Chapman at the National Museum of Victoria. Chapman was an authority on Foraminifera and was president of the Royal Society of Victoria. About her time at the Museum she wrote: “In the early days, we passed through the depression era. Our salaries were reduced overnight. I was reduced to six pounds a week. They were difficult times for us all. One would walk a long distance to save a threepenny tram fare.”

Dr Irene Crespin with W. Baragwanath, Secretary of Mines for Victoria, probably visiting a Cooksonia plant site, c. 1927 (From Turner 2007)

In 1936, Crespin succeeded Chapman as Commonwealth Palaeontologist. On February 10th, she was transferred from the National Museum, Melbourne to join the Commonwealth Geological Adviser, Dr. W.G. Woolnough, in Canberra. About her new position she wrote: “Of course, being a woman, and despite the tremendous responsibility placed upon me with the transfer to Canberra, I was given a salary of about half of that which Chapman received. Later the Chairman of the Public Service Board told me that I was being put on trial.”

She becoming greatly interested in the Tertiary microfaunas, and for some time she was the only professional micropaleontologist on the Australian mainland. Her research took her all over Australia. In 1939, she received permission from the Minister of the Interior to visit Java and Sumatra to discuss the problems of Tertiary correlation in the Netherlands East Indies with Papua and New Guinea.

Crespin’s photo of her aeroplane and crew on an overseas trip to Java, Indonesia, 1939 (From Turner 2007)

Crespin was well respected internationally and was a regular participant in national and international scientific conferences. In 1953, many of her books and specimens were destroyed as a result of a fire in the Canberra offices. The same year, she received Queen Elizabeth II’s coronation medal. In 1957 she was president of the Royal Society of Canberra, and was awarded with the Clarke medal of the Royal Society of New South Wales.

During her career she published 86 papers as sole author and more 22 in collaboration with other scientists. She was made an honorary fellow of the Royal Microscopical Society, London, in 1960. She became an honorary member of the Australian and New Zealand Association for the Advancement of Science in 1973. She died in Canberra, on January 2, 1980.

References:

Turner, S. (2007). Invincible but mostly invisible: Australian women’s contribution to geology and palaeontology. Geological Society, London, Special Publications, 281(1), 165–202. doi: 10.1144/sp281.11

Crespin, Irene (1975). “Ramblings of a micropalaeontologist”. BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS.

 

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Life finds a way.

 

Site M0077 in the Chicxulub crater as seen using gravity data. From Lowery et al., 2018.

In the late ’70, 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 an asteroid collided with the Earth and caused one of the most devastating events in the history of life. In 1981, Pemex (a Mexican oil company) identified Chicxulub as the site of this massive asteroid impact. The crater is more than 180 km (110 miles) in diameter and 20 km (10 miles) in depth, making the feature one of the largest confirmed impact structures on Earth.

The impact released an estimated energy equivalent of 100 teratonnes of TNT, induced earthquakes, shelf collapse around the Yucatan platform, and widespread tsunamis that swept the coastal zones of the surrounding oceans. The event also produced high concentrations of dust, soot, and sulfate aerosols in the atmosphere. The decrease of sunlight caused a drastic short-term global reduction in temperature (15 °C on a global average, 11 °C over the ocean, and 28 °C over land). While the surface and lower atmosphere cooled, the tropopause became much warmer, eliminate the tropical cold trap and allow water vapor mixing ratios to increase to well over 1,000 ppmv in the stratosphere. Those events accelerated the destruction of the ozone layer. During this period, UV light was able to reach the surface at highly elevated and harmful levels. Additionally, the vapour produced by the impact  could have led to global acid rain and a dramatic acidification of marine surface waters.

The Cretaceous/Palaeogene mass extinction eradicated almost three-quarters of the plant and animal species on Earth including non-avian dinosaurs, pterosaurs, marine reptiles, and ammonites. Global forest fires might have raged for months. Photosynthesis stopped and the food chain collapsed. Marine environments lost about half of their species, and almost 90% of Foraminifera species went extinct. But life always finds a way, and 30,000 years after the impact, a thriving ecosystem was present within the Chicxulub crater.

The evidence comes from the recent joint expedition of the International Ocean Discovery Program and International Continental Drilling Program. The team sampled the first record of the few hundred thousand years immediately after the impact within the Chicxulub crater. This sample includes foraminifera, calcareous nannoplankton, trace fossils and geochemical markers for high productivity. The lowermost part of the limestone sampled also contains the lowest occurrence of Parvularugoglobigerina eugubina, the first trochospiral planktic foraminifera, which marks the base of Zone Pα. This biozone was defined at Gubbio (Italy) to precisely characterise the Cretaceous/Paleogene boundary.

3 Early Danian foraminifer abundances and I/(Ca+Mg) oxygenation proxy. From Lowery et al., 2018.

P. eugubina was a low to middle latitude taxon with an open-ocean affinity and has an extremely variable morphology. Other foraminifer of the same genus (P. extensa, P. alabamensis) and Guembelitria cretacea were found at the same core. The nannofossil assemblage includes opportunistic groups that can tolerate high environmental stress such as Thoracosphaera and Braarudosphaera, but unlike the foraminifera, there are no clear stratigraphic trends in overall nannoplankton abundance. Discrete, but clear trace fossils, including Planolites and Chondrites, characterize the upper 20cm of the transitional unit. Nevertheless, the study also shows that photosynthetic phytoplankton struggled to recover for millions of years after the event.

Core samples also revealed that porous rocks in the center of the Chicxulub crater had remained hotter than 300 °C for more than 100,000 years. The high-temperature hydrothermal system was established within the crater but the appearance of burrowing organisms within years of the impact indicates that the hydrothermal system did not adversely affect seafloor life. These impact-generated hydrothermal systems are hypothesized to be potential habitats for early life on Earth and other planets.

 

Reference:

Christopher M. Lowery et al. Rapid recovery of life at ground zero of the end-Cretaceous mass extinction, Nature (2018). DOI: 10.1038/s41586-018-0163-6

Charles G. Bardeen, Rolando R. Garcia, Owen B. Toon, and Andrew J. Conley, On transient climate change at the Cretaceous−Paleogene boundary due to atmospheric soot injections, PNAS 2017 ; published ahead of print August 21, 2017 DOI: 10.1073/pnas.1708980114

Brugger J.G. Feulner, and S. Petri (2016), Baby, it’s cold outside: Climate model simulations of the effects of the asteroid impact at the end of the CretaceousGeophys. Res. Lett.43,  doi:10.1002/2016GL072241.

 

 

Late Cretaceous and modern diatom ecology: implications for our changing oceans

Sin título

Photomicrographs of diatom resting spores. Scale bars =10 mm (From Davies and Kemp, 2016)

Diatoms are unicellular algae with golden-brown photosynthetic pigments with a fossil record that extends back to Early Jurassic. They live in aquatic environments, soils, ice, attached to trees or anywhere with humidity, and their remains accumulate forming diatomite, a type of soft sedimentary rock. 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.

Past fluctuations in global temperatures are crucial to understand Earth’s climatic evolution. During the Late Cretaceous the global climate change has been associated with episodes of outgassing from major volcanic events, orbital cyclicity and tectonism before ending with the cataclysm caused by a large bolide impact at Chicxulub, on the Yucatán Peninsula, Mexico. Following a major diatom radiation after the Cenomanian-Turonian anoxic event, the development of the first extensive diatomites provides the earliest widespread geological evidence for the rise to prominence of diatoms in ocean biogeochemistry. Studies of the greenhouse Cretaceous climates are especially topical since such warm, high CO2 periods of the past are often invoked as potential analogues for present warming trends (Davies and Kemp, 2016).

A. Chain of Stephanopyxis turri (From

A. Chain of Stephanopyxis turri (From Davies and Kemp, 2016)

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. Like Stephanopyxis, a common planktonic genus in the present oceans distinguished by its long stratigraphic range from the Albian to modern. Stephanopyxis can be found in tropical or warm water regions and evidence suggests a similar ecological adaptation during the Cretaceous. Meanwhile, resting spore development is generally associated with the onset of unfavourable environmental conditions and sporulation generally occurs in response to a sudden change in one or more environmental factors.

Since the start of the Industrial Revolution the anthropogenic release of CO2 into the Earth’s atmosphere has increased a 40%. In this context, warming of the present surface ocean is  leading to increased stratification in both hemispheres. Based on traditional views of diatom ecology, ocean stratification would  lead to decreased diatom production and a reduced effectiveness of the marine biological carbon pump. But recent ocean surveys, and records of the stratified seas of the Late Cretaceous, suggest that increased stratification may lead to increased rather than decreased diatom production and export. This would then result in a negative-rather than positive feedback to global warming (Davies and Kemp, 2016).

 

References:

A. Davies, A.E.S. Kemp, Late Cretaceous seasonal palaeoclimatology and diatom palaeoecology from laminated sediments, Cretaceous Research 65 (2016) 82-111

Martin, R. E. and Quigg, A. 2012 Evolving Phytoplankton Stoichiometry Fueled Diversification of the Marine Biosphere. Geosciences. Special Issue on Paleontology and Geo/Biological Evolution. 2:130-146.

The Pliocene Warm Period, an analogue of a future warmer Earth.

 

Tuktoyuktuk Beach on the Arctic Ocean (From Wikipedia)

Tuktoyuktuk Beach on the Arctic Ocean (From Wikipedia)

Microfossils from deep-sea are crucial elements for our understanding of past and present oceans. Their skeletons take up chemical signals from the sea water, in particular isotopes of oxygen and carbon. Over millions of years, these skeletons accumulate in the deep ocean to become a major component of biogenic deep-sea sediments. The incorporation of Mg/Ca into the calcite of marine organisms, like foraminifera, is widely used to reconstruct the thermal evolution of the oceans throughout the Cenozoic. Planktic foraminifer Globigerinoides ruber is perhaps one of the most widely used species for reconstructing past sea-surface conditions. Additionally, Mg/Ca–oxygen isotope measurements of benthic foraminifera may be related to global ice volume and by extension, sea level (Evans et al., 2016). The importance of microfossils as tool for paleoclimate reconstruction was recognized early in the history of oceanography. John Murray, naturalist of the CHALLENGER Expedition (1872-1876) found that differences in species composition of planktonic foraminifera from ocean sediments contains clues about the temperatures in which they lived.

Scanning Electron Micrographs of Globigerinoides ruber (adapted from Thirumalai et al., 2014)

Scanning Electron Micrographs of Globigerinoides ruber (adapted from Thirumalai et al., 2014)

The most recent investigations have focused on unravelling the Pliocene Warm Period, a period proposed as a possible model for future climate. The analysis of the evolution of the major ice sheets and the temperature of the oceans indicates that during the middle part of the Pliocene epoch (3.3 Ma–3 Ma), global warmth reached temperatures similar to those projected for the end of this century, about 2°–3°C warmer globally on average than today.

The mid-Pliocene is used as an analog to a future warmer climate because it’s geologically recent and therefore similar to today in many aspects like the land-sea configuration, ocean circulation, and faunal and flora distribution. Mid- Pliocene sediments containing fossil proxies of climate are abundant worldwide, and many mid- Pliocene species are extant, making faunal and floral paleotemperature proxies based on modern calibrations possible (Robinson et al., 2012).

Surface air temperature anomalies of (top) the late 21st century and (bottom) the mid-Pliocene (from Robinson et al., 2012)

Surface air temperature anomalies of (top) the late 21st century and (bottom) the mid-Pliocene (from Robinson et al., 2012)

Foraminiferal Mg/Ca data suggest that the Pliocene tropics were the same temperature or cooler than present. At high latitudes, mid- Pliocene sea surface temperatures (SSTs) were substantially warmer than modern SSTs. These warmer temperatures were reflected in the vegetation of Iceland, Greenland, and Antarctica. Coniferous forests replaced tundra in the high latitudes of the Northern Hemisphere. Additionally, the Arctic Ocean may have been seasonally free of sea-ice, and were large fluctuations in ice cover on Greenland and West Antarctica (Dolan et al., 2011; Lunt et al., 2012).  These results highlights the importance of the Pliocene Warm Period to better understand future warm climates and their impacts.

Reference:

David Evans, Chris Brierley, Maureen E. Raymo, Jonathan Erez, Wolfgang Müller; Planktic foraminifera shell chemistry response to seawater chemistry: Pliocene–Pleistocene seawater Mg/Ca, temperature and sea level change; Earth and Planetary Science Letters, Volume 438, 15 March 2016, Pages 139-148

Jochen Knies, Patricia Cabedo-Sanz, Simon T. Belt, Soma Baranwal, Susanne Fietz, Antoni Rosell-Mel. The emergence of modern sea ice cover in the Arctic Ocean. Nature Communications, 2014; 5: 5608 DOI: 10.1038/ncomms6608

Robinson, M.; Dowsett, H. J.; Chandler, M. A. (2008). “Pliocene role in assessing future climate impacts”; Eos 89 (49): 501–502.

Application of diatoms to tsunami studies.

Lisbon earthquake and tsunami in 1755 (From Wikipedia Commons)

Lisbon earthquake and tsunami in 1755 (From Wikipedia 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. They live in aquatic environments, soils, ice, attached to trees or anywhere with humidity and their remains accumulates forming diatomite, a type of soft sedimentary rock. Diatoms are the dominant marine primary producers in the oceans and play a key role in the carbon cycle and in the removal of biogenic silica from surface waters. But diatoms are also a valuable tool in reconstructing paleoenvironmental changes because of their sensitivity to environmental factors including salinity, tidal exposure, substrate, vegetation, pH, nutrient supply, and temperature found in specific coastal wetland environments. Through years, diatoms become part of the coastal sediments, resulting in buried assemblages that represent an environmental history that can span thousands of years. Diatoms alone cannot differentiate tsunami deposits from other kinds of coastal deposits, but they can provide valuable evidence for the validity of proposed tsunami deposits (Dura et al., 2015).

Electron microscope image of Diatoms from high altitude aquatic environments of Catamarca Province, Argentina (From Maidana and Seeligmann, 2006)

Electron microscope image of Diatoms from high altitude aquatic environments of Catamarca Province, Argentina (From Maidana and Seeligmann, 2006)

Tsunami deposits can be identify by finding anomalous sand deposits in low-energy environments such as coastal ponds, lakes, and marshes. Those anomalous deposits are diagnosed using several criteria such as floral (e.g. diatoms) and faunal fossils within the deposits. The delicate valves of numerous diatom species may be unusually well preserved when removed from surface deposits and rapidly buried by a tsunami.

Diatoms within the tsunami deposits are generally composed of mixed assemblages, because tsunamis inundated coastal and inland areas, eroding, transporting, and depositing brackish and freshwater taxa. Nonetheless, problems differentiating autochthonous (in situ) and allochthonous (transported) diatoms complicates reconstructions. In general, planktonic diatoms are considered allochthonous components in modern and fossil coastal wetland assemblages, while benthic taxa can be considered as autochthonous. Diatoms can also be used to estimate tsunami run-up  by mapping the landward limit of diatom taxa transported by the tsunami.

 

References:

Hemphill-Haley, E., 1996. Diatoms as an aid in identifying late Holocene tsunami deposits. The Holocene 6, 439–448.

Tina Dura, Eileen Hemphill-Haley, Yuki Sawai, Benjamin P. Horton, The application of diatoms to reconstruct the history of subduction zone earthquakes and tsunamis, Earth-Science Reviews 152 (2016) 181–197. DOI: 10.1016/j.earscirev.2015.11.017

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

Barron, J.A. (2003). Appearance and extinction of planktonic diatoms during the past 18 m.y. in the Pacific and Southern oceans. “Diatom Research” 18, 203-224

Alcide d’Orbigny and the beginning of foraminiferal studies.

Alcide_Dessalines_d'Orbigny_1802

Alcide Dessalines d’Orbigny , 1802. From Wikimedia Commons

During the eighteenth and nineteenth centuries, Paris was a busy place for science. In 1794 the Reign of Terror ended with the establishment of a new government that was more supportive of the sciences. The old Royal Botanical Garden and the affiliated Royal Museum were reorganized as the Muséum national d’histoire naturelle. The new institution fostered many brilliant scientists, including Cuvier, Lamarck, and St. Hilaire. Among those remarkable men was Alcide Dessalines d’Orbigny, considered the founder of micropaleontology and biostratigraphy. He worked in natural history, geology, paleontology, anthropology, linguistics, taxonomy and systematics.

Alcide d’Orbigny was born in Couëron (Charente-Maritime) on September 6th, 1802. In his early youth, he developed a life interest in the study of a group of microscopic animals that he named ‘Foraminifera’ and established the basis of a new science, micropaleontology. He started at an early age working with his father, a doctor, who introduced him to the study of microscopic shells they collected from La Rochelle, a major port on the coast of France. However, Bartolomeo Beccari, was the first to study these tiny shells that could only be observed under the microscope. Beccari analysed in detail the outer and inner structure of the shell, recognising the concamerations and the coiled structure, and attributed these organisms to microscopic ‘Corni di Ammone’, continuing with the enduring confusion between ammonites and foraminifera that started in 1565 when Conrad Gesner described the nummulites collected in the surroundings of Paris. Also Giovanni Bianchi (known by the pseudonym Jaco Planco) in his work De conchis minus notis’ (1739) describes numerous microforaminifera that are found in abundance on the shoreline of Rimini and assigns them the name ‘Corni di Ammone’.

Cover of De conchis minus notis and foraminifera of Rimini’s seaside figured by Bianchi (1739, Table I) and attributed by the author to microscopic specimens of ‘Cornu Ammonis’.

Cover of De conchis minus notis and foraminifera of Rimini’s seaside figured by Bianchi (1739, Table I) and attributed by the author to microscopic specimens of ‘Cornu Ammonis’.

On November 7, 1825, d’Orbigny presented to the Académie des Sciences, the results of his observations in a work entitled ‘Tableau méthodique de la classe des Céphalopodes’. It’s clear that d’Orbigny also considered this group of  microscopic shells as belonging to the Cephalopods. But he was the first to divide the Cephalopods into two zoological orders:  the ‘Siphonifères‘ with intercameral siphon and ‘Foraminifères’ characterized by openings (or foramina) located in the septa separating two consecutive chambers. To illustrate his work, d’Orbigny prepared 73 plates of drawings and made models of 100 of his foraminiferal species that he sculpted in a very fine limestone.

There is a long gap between the publication of his pioneering work and his other works dedicated to foraminifera because of his long journey to South America documented in the nine volumes of his ‘Voyage dans l’Amérique Méridionale’ (1835–1847). In 1835, Félix Dujardin discovered that foraminiferans were not cephalopods, but single-celled organisms. This important discovery led d’Orbigny to exclude the foraminifera from the Cephalopods. In a work published in 1839, he traced the history of foraminiferal studies and considered them as a class for the first time, dividing the history of their study in four periods culminating with the revelation of their unicellular nature.

Operculina, showing the details of d’Orbigny’s drawings intended for the Tableau.

Operculina, showing the details of d’Orbigny’s drawings intended for the Tableau.

In the volume dedicated to the recent foraminifera collected in South America he pointed out the influence of currents, temperature and depth on their distribution patterns. In Mémoire sur les foraminifères de la craie blanche du bassin de Paris published in 1840, d’Orbigny demonstrated that foraminifera could be used for classifying geological strata.

D’Orbigny‘s legacy was extraordinary with thousands of species described, the occurrences of fossils documented chiefly in France, as well as his outstanding Le Voyage dans l’Amérique méridionale published between 1835-1847, and covering the biology, ethnology, anthropology, paleontology, and other aspects of Chile, Peru, Argentina, Uruguay, and especially Bolivia.

In 1853, Napoleon III created the Chair of Paleontology in the Muséum national d’Histoire naturelle in his honour. After his death on June 30, 1857, the collection of d’Orbigny, which includes more than 14,000 species and over 100,000 specimens not counting innumerable foraminifera stored in assorted glass bottles, was auctioned by his family. The collection was bought by the Muséum National d’Histoire Naturelle, in 1858 and registered in the catalogue of the Paleontology Laboratory of this institution.

 

References:

d’Orbigny, A. 1826. Tableau méthodique de la classe des Céphalopodes. Annals des Sciences Naturelles, 1st Series, 7: 245-314.
Dujardin, F. 1835a. Observations sur les Rhizopodes et les Infusoires, Comptes Rendus, de l’Académie des Sciences, 1: 338-340.

Heron-Allen, E. (1917) Alcide d’Orbigny, his life and his work. Journal of the Royal Microscopic Society, ser. 2, 37, 1–105, 433–4.

Seguenza G. 1862. Notizie succinte intorno alla costituzione geologica dei terreni terziarii del distretto di Messina. Messina: Dalla Stamperia di Tommaso Capra. 84 pp.

Vénec-Peyré, M-T, 2004, Beyond frontiers and time: the scientific and cultural heritage of Alcide d’Orbigny (1802–1857), Marine Micropaleontology 50, 149 – 159.

Response of marine ecosystems to the PETM.

Biotic change among foraminifera during and after the PETM. (From Speijer et al., 2012)

Biotic change during and after the PETM. (From Speijer et al., 2012)

The Paleocene-Eocene Thermal Maximum (PETM; 55.8 million years ago), was a short-lived (~ 200,000 years) global warming event attributed to a rapid rise in the concentration of greenhouse gases in the atmosphere. It was suggested that this warming was initiated by the melting of methane hydrates on the seafloor and permafrost at high latitudes. During the PETM, around 5 billion tons of CO2 was released into the atmosphere per year, and temperatures increased by 5 – 9°C. This event was accompanied by other large-scale changes in the climate system, for example, the patterns of atmospheric circulation, vapor transport, precipitation, intermediate and deep-sea circulation and a rise in global sea level.

Dinoflagellate cysts: Adnatosphaeridium robustum and Apectodinium augustum (From Sluijs and Brinkhuis, 2009)

Dinoflagellate cysts: Adnatosphaeridium robustum and Apectodinium augustum (From Sluijs and Brinkhuis, 2009)

The rapid warming at the beginning of the Eocene has been inferred from the widespread distribution of dinoflagellate cysts. One taxon in particularly, Apectodinium, spans the entire carbon isotope excursion (CIE) of the PETM. The distribution of Apectodinium is linked to high temperatures and increased food availability.

The most disruptive impact during the PETM was likely the exceptional ocean acidification and the rise of the calcite dissolution depth, affecting marine organisms with calcareous shells (Zachos et al., 2005). When CO2 dissolves in seawater, it produce carbonic acid. The carbonic acid dissociates in the water releasing hydrogen ions and bicarbonate. The formation of bicarbonate then removes carbonate ions from the water, making them less available for use by organisms.

Nannofossil abundance changes during the PETM. (From Kump, 2009.)

Nannofossil abundance changes during the PETM. (From Kump, 2009.)

The PETM onset is also marked by the largest deep-sea mass extinction among calcareous benthic foraminifera (including calcareous agglutinated taxa) in the last 93 million years. Similarly, planktonic foraminifera communities at low and high latitudes show reductions in diversity, while larger foraminifera are the most common constituents of late Paleocene–early Eocene carbonate platforms.

The response of most marine invertebrates (mollusks, echinoderms, brachiopods) to paleoclimatic change during the PETM is poorly documented.

Coccolithus bownii and Toweius pertusus

Coccolithus bownii and Toweius pertusus (Adapted from Bown and Pearson, 2009)

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 combination of global warming and the release of large amounts of carbon to the ocean-atmosphere system during the PETM has encouraged analogies to be drawn with modern anthropogenic climate change. 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.

Comparison of the effects of anthropogenic emissions (total of 5000 Pg C over 500 years) and PETM carbon release (3000 Pg C over 6 kyr) on the surface ocean saturation state of calcite. From Zeebe, 2013

Comparison of the effects of anthropogenic emissions (total of 5000 Pg C over 500 years) and PETM carbon release (3000 Pg C over 6 kyr) on the surface ocean saturation state of calcite. From Zeebe, 2013

 

References:

Maria Rose Petrizzo, The onset of the Paleocene–Eocene Thermal Maximum (PETM) at Sites 1209 and 1210 (Shatsky Rise, Pacific Ocean) as recorded by planktonic foraminifera, Marine Micropaleontology, Volume 63, Issues 3–4, 13 June 2007, Pages 187-200

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.

Wright JD, Schaller MF (2013) Evidence for a rapid release of carbon at the Paleocene-Eocene thermal maximum. Proc Natl Acad Sci USA 110(40):15908–15913.

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

Raffi, I. and de Bernardi, B.: Response of calcareous nannofossils to the Paleocene-Eocene Thermal Maximum: observations on composition, preservation and calcification in sediments from ODP Site 1263 (Walvis Ridge – SW Atlantic), Mar. Micropaleontol., 69, 119–138, 2008.

Robert P. SPEIJER, Christian SCHEIBNER, Peter STASSEN & Abdel-Mohsen M. MORSI; Response of marine ecosystems to deep-time global warming: a synthesis of biotic patterns across the Paleocene-Eocene thermal maximum (PETM), Austrian Journal of Earth Sciences. Vienna. 2012. Volume 105/1.

Haeckel and the legacy of early radiolarian taxonomists.

Ernst Haeckel and his assistant Nicholas Miklouho-Maclay, photographed in the Canary Islands in 1866. From Wikimedia Commons.

Ernst Haeckel and his assistant Nicholas Miklouho-Maclay, photographed in the Canary Islands in 1866. From Wikimedia Commons.

In the nineteenth century, the study of radiolarians was the domain of German scientists. These early German workers laid the foundation for all future work with this group of organisms, both living and fossil.

Christian Gottfried Ehrenberg (1795–1876) made a series of special monographs from 1838 to 1875 and named the group Polycystina. He described a half-dozen species of both Spumellaria and Nassellaria. Ehrenberg’s microscopic researches also included diatoms and  fossil cyst of dinoflagellates. His book “Mikrogeologie” (1854) has many illustrations of a great number of microfossils.

Many of Ehrenberg’s early radiolarian species descriptions come from Neogene biosiliceous sediments of Italy. Despite the fact he worked before the concept of type specimens for species had become established, Ehrenberg not only documented most of his species with published figures, but preserved the original material and microscope preparations for future generations of scientists to study (Lazarus 2014).

Christian Gottfried Ehrenberg and Johannes Müller. Source: Museum für Naturkunde, Berlin and Humboldt Universität, Berlin.

Christian Gottfried Ehrenberg and Johannes Müller. Source: Museum für Naturkunde,
Berlin and Humboldt Universität, Berlin.

Johannes Müller (1801–1858), one of the most famous German biologists of his generation, published three substantial papers on radiolarians. He described a total of 69 species, including both polycystines and acantharians. As a professor on Berlin’s Medical Faculty, he  influenced a great number of students. Among them were Ernst Haeckel (1834-1919) and Rudolf Virchow (1821-1902).

Like  Ehrenberg, Müller never believed that species had evolved over time, and he died before the publication of Charles Darwin’s Origin of Species.

After Müller’s death, E. Haeckel focused on the group last studied by his friend and professor: the radiolarians. With a copy of Müller’s paper and a wealth of material available off Messina, Haeckel began the first of his major studies of nature.

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In 1862, Haeckel made the first complete  classificatory system for the Radiolaria and produced finely detailed drawings of them in his book: “Die Radiolarien”. He dedicated this monograph to Müller. In this work, he  included polycystines, phaeodarians and acantharians.

In 1864, Haeckel sent to Darwin, two folio volumes on radiolarians. The gothic beauty of these drawings impressed Darwin. He wrote to Haeckel that “were the most magnificent works which I have ever seen, and I am proud to possess a copy from the author”.

Haeckel became the most famous champion of Darwinism in Germany and he was so popular that, previous to the First World War, more people around the world learned about the evolutionary theory through his work “Natürliche Schöpfungsgeschichte” (The History of Creation: Or the Development of the Earth and its Inhabitants by the Action of Natural Causes) than from any other source. His study of radiolarians established Haeckel as a young scientist of importance. Later, Haeckel focused his research in the more general aspects of evolution and development.

Ernst Haeckel's ''Kunstformen der Natur'' (1904), showing Radiolarians of the order Stephoidea. From Wikimedia Commons.

Ernst Haeckel’s ”Kunstformen der Natur” (1904), showing Radiolarians of the order Stephoidea. From Wikimedia Commons.

Along with many other scientists, Haeckel was asked by the managers of the Challenger Expedition soon after the ship’s return to examine and report on the expedition’s collections specifically for radiolarians, sponges and jellyfish. Haeckel’s Report on Radiolaria took him almost a decade.

His final report was published in 1887 and summarized and subsumed all prior work on radiolarians up to that point, including, for example, many of Ehrenberg’s species and genera. But while Ehrenberg eschewed higher taxa, except for a minimally adequate number of obvious, high-level groupings, Haeckel did the opposite thing and introduced a much enlarged and substantially more complex higher-level taxonomy for the radiolaria generating numerous duplicate lower-level categories, including species, which led to an unusually large percentage of Haeckel’s named species being ignored as redundant or meaningless (Lazarus, 2014).

In 1904, Haeckel published his master work “Kunstformen der Natur” (Art Forms of Nature) and helped to popularize radiolarians among scientists and the general audience.

Radiolaria illustration from the Challenger Expedition 1873–76. From Wikimedia Commons.

Radiolaria illustration from the Challenger Expedition 1873–76. From Wikimedia Commons.

Karl Alfred Ritter von Zittel (1839-1904), was a prominent German paleontologist.  His early research was in minerals and petrography. In 1876, he published “Ueber einige fossile Radiolarien aus der norddeutschen Kreiden. Zeitschrift der deutschen geologischen Gesellschaft” where he described Mesozoic radiolarians in northern Germany. Many of the species names proposed by Zittel are still valid today.

David Rüst (1831–1916) published 10 papers on radiolarians. Although he was not the first to describe Mesozoic radiolarians, he was certainly the most prolific describing over 900 new species of fossil radiolarians from Mesozoic and even Palaeozoic rocks from Europe and North America.

 

References:

David Lazarus, The legacy of early radiolarian taxonomists, with a focus on the species published by early German workers, Journal of Micropalaeontology 2014, v.33; p3-19.

Robert J. Richards, The Tragic Sense of Life: Ernst Haeckel and the Struggle over Evolutionary Thought, (2008), University of Chicago Press.

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

 

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