Using Cliffs on Earth to Understand Water Flow on Ancient Mars

Prolonged Fluvial Activity From Channel-Fan Systems on Mars

by: Gaia Stucky de Quay, Edwin S. Kite, and David P. Mayer 

Summarized by: Lisette Melendez

What data were used? In geology, there’s a basic pillar called “The Principle of Uniformitarianism”. It suggests that geologic processes almost always occur in the same manner and intensity now as they did in the past – which is why geologists can look at the rock record to learn more about Earth’s future. In the same vein, many geologic processes that occur on Earth, like landslides, volcanoes, and erosions, can be used to study the same processes on different planets!

This study focused on analyzing pictures of alluvial fans (finger-like deposits that are usually created when running water in arid or semi-arid (e.g., deserts) flows downhill onto a flat surface, as shown in Figure 1) on Mars taken by the Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO). The scientists also compared Martian alluvial fans to the ones found here on Earth using elevation data collected by the NASA Shuttle Radar Topography Mission. These alluvial fans usually mark the end of a water channel, so they can be used to study ancient water deposits on Mars.       

Figure 1: An example of an alluvial fan on the surface of Mars, taken by the Mars Reconnaissance Orbiter.

Methods: To study the channels of Mars, the CTX images were converted into digital elevation models, so information like width, slope, and height could be gathered from the data. The valleys on Mars were also measured for how closely they resembled a V-shape. Valleys shaped by rivers have a V-shape, while valleys shaped by other features, like glaciers, tend to have a U-shape.

After gathering all this data, the scientists desired to make an inference about the sediment on Mars, which is too small to be picked up by the camera. So, they turned to places on Earth that had alluvial fans that were very similar to the ones being studied on Mars: the Serra Geral in Brazil, the Great Escarpment in western South Africa, and the Western Ghats in India. These places were ideal parallels for the Martian surface because there’s little to no active tectonic plate movement in the area and the rocks are very well preserved over a long period of geologic time. The big difference is that instead of being placed along mountainsides or plateaus, the slopes that are being studied on Mars are usually along crater rims. 

Results: The channels studied on Mars were found to be less concave (curved inwards) and have very steep slopes, indicating a dry environment. The data on concavity and erodibility (likeliness to erode away) on the Martian alluvial fans was most similar to the data found on the South African slopes, which reinforces the idea that the environment was similarly hot and dry.

Figure 2: The cliffs of Earth (Brazil, South Africa, and India) used to study the sediment on the Martian surface.

Why is this study important? This study is another piece of evidence behind the idea that Mars was once full of water, before it underwent serious climate change. Understanding the history of water on Mars is crucial to understanding what conditions are necessary for life to evolve (which can help paleontologists learn about the first life on Earth, too!). It’s also interesting to note how we can learn more about planets that are millions of miles away by looking right here on Earth!

 The big picture: More than a billion years ago, water used to run freely on the surface of Mars, creating channels and alluvial fans. Scientists use images of the geologic features that remained after water was no longer on the Martian surface to learn more about the history of the Red Planet and the potential implications for human exploration. Learning more about the surface and climate of Mars is necessary for understanding the hazards and potential resources that would be encountered on a crewed mission to Mars.

Citation: Stucky de Quay, G., Kite, E. S., & Mayer, D. P. ( 2019). Prolonged fluvial activity from channel‐fan systems on Mars. Journal of Geophysical Research: Planets, 124, 3119– 3139.  https://doi.org/10.1029/2019JE006167

Understanding how Tectonic Activity affected Triassic Vegetation and Climate

Triassic vegetation and climate evolution on the northern margin of Gondwana: a palynological study from Tulong, southern Xizang (Tibet), China

by: Jungang Peng, Jianguo Li, Sam M. Slater, Qianqi Zhanga, Huaicheng Zhu, Vivi Vajda

Summarized by: Kailey McCain

What data were used? Researchers noticed that while there was extensive research in North American and European paleobotany (i.e., plant fossils) from the Triassic period, data was very limited for Southern Asia. To fill this gap in knowledge, 147 samples were collected across China and examined for pollen, dust, and other microscopic fossils (also known as palynomorphs). Additionally, rock samples that dated through the Early Triassic were collected and processed. 

Methods: The samples were processed using hydrochloric acid (HCl is strong acid and has a low pH value ~1) and hydrofluoric acid (HF is a weak acid and has a higher pH value ~6) lab techniques. By using these acids, the microfossils were isolated from the sediment sample and placed on a microscope slide for further investigation. 

The palynology samples were tested for pollen and spores (cells that are capable of developing into a new individual without another reproductive cell). The abundance of specific species were then mapped to illustrate vegetation and climate during the Olenekian, a period of time during the Early Triassic. The identified microfossils can be seen in figure 1. 

Results: The data collected showed that there are roughly three vegetation stages throughout the Early Triassic. The first stage is dominated by pteridosperms (fern-like vegetation lacking spores), which indicated a warm and dry climate. The following stage exhibited a decrease in pteridosperms and an increase in conifers (woody plants). This change in vegetation indicates a decrease in temperature and an increase in humidity. The final stage exhibits a steady increase in conifers and a diverse range in ferns, thus indicating a stable and temperate climate.

Using these stages, researchers were then able to compare the shifts in vegetation and climate to the tectonic activity due to the rifting (splitting) of Gondwana, an ancient supercontinent that split from Pangea. Through the examination of the rifts and ocean levels, the researchers hypothesized that the separation of Gondwana was a driving factor in regional climate and vegetation shifts. 

Figure 1: This image shows some of the microscopic pollen and spore fossils identified. Additionally, the image shows a scale bar (located under F and G) that represents 20 micrometers (µm), which is 1,000,000 times smaller than a meter!

Why is this study important? This study provided insights into the ways tectonic activity affected the environment in an area that lacked prior research. It drew important correlations between climate and tectonic activity. Additionally, evaluating the specific abundance and lack of certain vegetation helps establish evolutionary patterns not only in the Triassic, but also in supercontinents. 

The big picture: Paleobotany and palynological data paint a great picture of what Earth was like during certain time periods. Specifically, the data collected in this study shows a correlation in Triassic vegetation and climate evolution during the rifting of Gondwana in Southern Asia.

Citation: Triassic vegetation and climate evolution on the northern margin of Gondwana: a palynological study from Tulong, southern Xizang (Tibet), China. (2019). Journal of Asian Earth Sciences, 175, 74–82. https://doi.org/10.1016/j.jseaes.2018.06.005

Experimental evidence for correlation between leaf shape and temperature in different plant species: suggestions for inferring paleoclimate

Experimental evidence for species-dependent responses in leaf shape to temperature: Implications for paleoclimate inference

by: Melissa L. McKee, Dana L. Royer, Helen M. Poulos

Summarized by: Mckenna Dyjak

What data were used?: Four species of seeds from woody plants were used: Boxelder Maple (Acer negundo L.), Sweetbirch (Betula lenta L.), American Hornbeam (Carpinus caroliniana Walter), and Red Oak (Quercus rubra L.). Three species from transfered saplings were also used: Red Maple (Acer negundo), American Hornbeam (Carpinus caroliniana Walter), and American Hophornbeam (Ostrya virginiana  K.Ko(Mill.)ch). The types of species were chosen because they each exist naturally along the east coast of the United States and have leaf shapes that vary with climate.

Methods:The seeds and saplings were randomly divided into either warm or cold treatments. The warm treatment cabinet had a target average temperature of 25°C (77°F) and the cold treatment cabinet had a target average temperature of 17.1°C (63°F). After three months, five fully expanded leaves were harvested and photographed immediately. The images from the leaves were altered in Photoshop (Adobe Systems) to separate the teeth (zig-zag edges of leaves) from the leaf blade (broad portion of the leaf). The leaf physiognomy (leaf size and shape) was measured using a software called ImageJ. The measured variables were tooth abundance, tooth size, and degree of leaf dissection. The degree of leaf dissection or leaf dissection index (LDI) is calculated by leaf perimeter (distance around leaf) divided by the square root of the leaf area (space inside leaf). The deeper and larger the space between the teeth of the leaf, the greater the LDI.

Results:The leaf responses to the two temperature treatments are mostly consistent with what is observed globally: the leaves from the cool temperature treatment favored having more teeth, larger teeth, and a higher LDI (higher perimeter ratio). However, it was found that the relation between leaf physiognomy (leaf size and shape) and temperature was specific to the type of species. 

Fig.1 Tooth abundance in relation to temperature. The colder temperature (in blue) correlates with an increasing number of teeth in generally all of the plant species tested. The differences can also be observed in the pictures present below the graphs. More leaf teeth (serrated edges along the margins) can be seen under the cold treatment.

Why is this study important?: Paleoclimate (past climate) can be determined by using proxy data which is data that can be preserved things such as pollen, coral, ice cores, and leaves. Leaf physiognomy can be used in climate-models to reconstruct paleotemperature from fossilized leaves. This study supports the idea that leaf size changes correlate with temperature change. However, the responses varied by species and this should be taken into account for climate-models using leaf physiognomy to infer paleoclimate. 

The bigger picture: Studying paleoclimate is important to see how past plants reacted to climate change so we have an idea how plants will respond to modern human-driven climate change.

Citation: McKee ML, Royer DL, Poulos HM (2019) Experimental evidence for species-dependent responses in leaf shape to temperature: Implications for paleoclimate inference. PLoS ONE 14(6): e0218884. https://doi.org/10.1371/journal.pone.0218884

Reef growth on the Great Barrier Reef in response to sea-level rise

A new model of Holocene reef initiation and growth in response to sea-level rise on the Southern Great Barrier Reef

by: Sanborn et al. 

Summarized by: Baron Hoffmeister

What data were used?: This study analyzed sediment cores taken from the One Tree Reef of the Southern Great Barrier Reef in Queensland, Australia. Data was collected from the layers and sediment grains found within core samples taken from 12 different locations on the reef.

Methods: This study used biogenetic facies interpretation (i.e. physical, chemical, and biological aspects found within sediment and rock formations) from core samples to reconstruct reef growth and sea-level conditions.

Results: This study concluded that reef growth after a significant sea-level rise in the Pleistocene occurred in three stages. The first stage occurred over eight thousand years ago and was a rapid and shallow coral growth in presumably clear water. The average growth was around 6mm per year. The second stage of reef growth was between seven to eight thousand years ago, and this occurred with either turbid (i.e. cloudy water) or deeper water (i.e. over 5 meters in depth) conditions. The average growth was around 3mm per year. The third stage of growth was composed of shallow branching coral assemblages averaging 5mm of growth per year. This was referred to as a “catch up” in the reef growth sequence and continued until the reef reached the top of the sea level. It is hypothesized that more sediment-tolerant corals continued to slowly build up across the reef during this time. These are the types of corals that are now dominant on the Great Barrier Reef. This study also successfully identified six coral assemblages, and three algae assemblages correlating with specific paleoenvironments, creating a new model (see figure 1) for interpretation of samples containing similar assemblages for future studies. Using geochronology (i.e. dating rock formations) a lag of 700-1000 years of reef growth was confirmed in this experiment. There was a significant gap of growth on the wind-sheltered portion of the reef, which is the opposite of what was hypothesized previously (that corals would grow faster in wind-sheltered areas). Figure 1 shows a new model for reef growth response from the results found in this study.

Figure 1. The new model for reef growth after the flooding of the Pleistocene basement (the bottom most rock layer). This graph describes the One Tree Reef Holocene growth. This includes the three phases of growth and the composition of these three growth stages with its corresponding depth.

Why is this study important?  This study is important for determining how corals and other reef-building organisms respond to environmental change and stress like sea-level change. Understanding past environmental conditions are crucial for understanding how current environmental conditions can affect reef growth today.

The big picture: This study not only provides new and important data of reef growth response to historical climatic changes but can also be used to predict present-day reef response to sea-level change. As sea level continues to occur, a more comprehensive understanding of the way coral and reef-building organisms respond to environmental changes could lead to preserving the reefs as the ocean conditions change. The new model this study found can provide important data for how reefs grow, and provide important paleoenvironmental interpretation data.  

Citation: Sanborn, Kelsey L., Jody M. Webster, Gregory E. Webb, Juan Carlos Braga, Marc Humblet, Luke Nothdurft, Madhavi A. Patterson et al. “A new model of Holocene reef initiation and growth in response to sea-level rise on the Southern Great Barrier Reef.” Sedimentary Geology 397 (2020): 105556. https://doi.org/10.1016/j.sedgeo.2019.105556

Understanding the geologic history of a near-Earth Asteroid through the lens of NASA’s OSIRIS-Rex mission

Craters, Boulders, and Regolith of (101955) Bennu Indicative of an Old and Dynamic Surface

by: K. J. Walsh, E. R. Jawin, R.-L. Ballouz, O. S. Barnouin, E. B. Bierhaus, H. C. Connolly Jr., J. L. Molaro, T. J. McCoy, M. Delbo’, C. M. Hartzell, M. Pajola, S. R. Schwartz, D. Trang, E. Asphaug, K. J. Becker, C. B. Beddingfield, C. A. Bennett, W. F. Bottke, K. N. Burke, B. C. Clark, M. G. Daly, D. N. DellaGiustina, J. P. Dworkin, C. M. Elder, D. R. Golish, A. R. Hildebrand, R. Malhotra, J. Marshall, P. Michel, M. C. Nolan, M. E. Perry, B. Rizk, A. Ryan, S. A. Sandford, D. J. Scheeres, H. C. M. Susorney, F. Thuillet, D. S. Lauretta and the OSIRIS-REx Team

Summarized by: Lisette Melendez

What data were used? Unlike geologic sites on Earth, scientists aren’t able to use field work to determine the geologic history of celestial objects like asteroids, planets, and distant moons. Instead, planetary geologists rely on data collected by scientific instruments on spacecraft, like cameras and spectrometers, to study these unreachable geologic features.

The data for this study was gathered from images taken by NASA’s ORISIS-Rex spacecraft, whose mission is to travel to a near-Earth asteroid named Bennu. Asteroids are the remains of the building blocks of our solar system that enabled the rise of planets and life, and most of them reside in the Main Asteroid Belt. However, sometimes asteroids are ejected and enter the inner solar system (i.e. the rocky planets: Mercury, Venus, Earth, and Mars), becoming near-Earth asteroids. This asteroid, Bennu, was chosen for the sample collection mission because of its proximity to Earth, large size (almost 500 meters long!), and carbonaceous (i.e., carbon-rich) composition. The carbon-rich part is important because these asteroids contain chemical compounds and amino acids that would have been present at the beginning of our Solar System. Even though the asteroid is relatively long compared to other asteroids, it’s only about as wide as the length of the Empire State Building!

The spacecraft is set to bring back a sample of this asteroid to Earth by 2023 for scientists to analyze. In late 2018, the spacecraft began the approach phase of the mission and used its cameras to take high-quality pictures of Bennu’s surface, as shown in Figure 1. These images are not only used to determine a good sample collection site, but scientists also use them to learn more about the geologic processes on Bennu’s surface. By weaving the images together, the team was able to produce a three-dimensional model of the asteroid and determine the location of boulders on the surface of Bennu. 

Figure 1: Shows the size of various boulders on Bennu’s surface. The arrows point towards identified fractures, which may be indicative of large impact events or stress caused by rapid temperature changes.

Methods: The surface of Bennu was mapped out by visually analyzing images taken by cameras on OSIRIS-Rex. Scientists combined image and radar data to measure the size and distribution of boulders on Bennu’s surface. By applying the same foundational geologic concepts observed here on Earth, scientists can draw conclusions about the geologic features on asteroids and what forces potentially formed them. 

Results: The orbit of a near-Earth asteroid is tumultuous, due to the possibility of collision with other asteroids and the forces exerted by Earth’s gravity, making a usual lifespan of a near-Earth asteroid only last around tens of millions of years. Usually, this would mean a young, consistently refreshed surface for these near-Earth asteroids. However, a detailed study of Bennu’s surface shows evidence of rocks that are hundreds of millions of years old – long before Bennu ever left the Main Asteroid Belt. 

Boulders are the most prominent geologic feature on Bennu’s surface. As shown in Figure 2, they can be found all around the asteroid. Scientists noted that the size of various boulders are simply too large for them to have been formed in Bennu’s current orbit, pointing towards the possibility they were created during larger asteroid collisions in the main asteroid belt. This indicates that studying the boulders further may aid in the understanding of Bennu’s parent body (i.e., where the rocks were originally created) and conditions in the main asteroid belt.

Another interesting result from the study is that even though the resolution of the images was not clear enough to depict fine-grained particles, the scientists measured thermal inertia (tendency to resist changes in temperature) and found that the results were consistent with the existence of fine-grained particles on Bennu’s surface. Come the end of 2020, the spacecraft will start up the TAGSAM (Touch-and-Go-Sample-Acquisition-Mechanism) instrument, blow nitrogen gas onto the surface to stir up dust, and collect the sample – leading to even more scientific discoveries on the asteroid front.  

Figure 2: Maps the abundance of boulders on Bennu’s surface, where red marks areas that are densely populated by boulders and blue marks areas where there are relatively less boulders.

Why is this study important? This study is a reminder of how fascinating geology is: scientists were able to predict the history of the asteroid solely by measuring the size and distribution of boulders on its surface. This group was able to differentiate between events that occurred while Bennu was in the Main Asteroid Belt versus a near-Earth orbit, which helps us understand the environment right outside of Earth and beyond. 

The big picture: By looking into the early Solar System, the data gathered in this study will help scientists understand the processes behind the formation of planets, as well as the origins of life. Additionally, the study will enhance our understanding of the evolution of near-Earth asteroids as well as the possibility of the asteroids impacting Earth.

Citation: Walsh, K.J., Jawin, E.R., Ballouz, R. et al. Craters, boulders and regolith of (101955) Bennu indicative of an old and dynamic surface. Nat. Geosci. 12, 242–246 (2019). https://doi.org/10.1038/s41561-019-0326-6

We’ve Seen This Before: What The Extinctions in Our Geologic Past Indicate About the Dangers of Current CO2 Emissions

Deep CO2 in the end-Triassic Central Atlantic Magmatic Province

Manfredo Capriolo, Andrea Marzoli, László E. Aradi, Sara Callegaro, Jacopo Dal Corso, Robert K. Newton, Benjamin J. W. Mills, Paul D. Wignall, Omar Bartoli, Don R. Baker, Nasrrddine Youbi, Laurent Remusat, Richard Spiess, and Csaba Szabó

Summarized by Lisette Melendez. 

What data were used? 

This study investigates the large-scale volcanic activity that would eventually lead to the end-Triassic Extinction, one of the top five most devastating extinction events for life on Earth, that occurred about 201 million years ago. The volcanic eruptions took place across the globe, leading to a massive sheet of volcanic rocks known as the Central Atlantic Magmatic Province, or CAMP for short. Considering that the volcanic activity took place before the supercontinent Pangea was fully split apart, CAMP rocks can be found in North America, Africa, and Europe, as shown in Figure 1. Scientists used both intrusive (magma that crystallized underground) and extrusive (magma that cooled on the Earth’s surface) rock samples to investigate the amount of carbon dioxide, a greenhouse gas, released into the atmosphere during these catastrophic eruptions.

Methods: By analyzing the concentration of the carbon dioxide bubbles (Figure 2) trapped within the crystals that were formed during the volcanic eruptions, scientists can determine the speed and frequency of the eruptions. After collecting more than 200 samples, the concentration of carbon dioxide within the rocks was determined using microspectroscopy: a method that shows the spectra of the sample in order to identify and quantify the various compounds that are present. 

Results: Overall, there was a high volume of carbon dioxide bubbles within CAMP rocks. Since CO2 is an accelerant for magma eruptions, the volcanic activity was likely hasty and violent. The rapid rise of CO2 in the environment means CO2-removing mechanisms, like weathering, aren’t enough to balance out the excess CO2. This leads to a carbon dioxide buildup in the atmosphere, accelerating global warming and ocean acidification.

 

Figure 1: A map of the boundaries Central Atlantic Magmatic Province in central Pangea, around 200 million years ago. It shows how wide-spread the volcanic eruptions were during this time.

Why is this study important? The study of CO2 saturation in rocks helps us understand the role that volcanism played in the buildup of excessive greenhouse gases in the atmosphere that triggered the end-Triassic extinction. It showed that the more rapid the release of CO2 into the atmosphere is, the more severe the environmental impact.

The big picture: This study can be used as a warning for current trends, considering that the amount of CO2 emitted during the CAMP eruption roughly equals the amount of projected anthropogenic (i.e., human-caused) emissions over the 21st century. Just like in the past, the current substantial rise in CO2 is leading to a global temperature increase and a surge in ocean acidification, but we are releasing CO2 much faster than at any other time in Earth’s history. Considering that these are the same conditions that led to one of the worst biotic extinctions in Earth’s history, it is vital to encourage our governments to implement radical climate change policies in order to slow the current rise of CO2 to prevent more environmental destruction. 

Figure 2: The black arrows point towards the bubble-bearing inclusions within the rock samples using light optical microscopy. The high concentration of CO2 within these bubbles indicates the magma was rich in CO2. These four samples are specifically orthopyroxene (Opx), clinopyroxene (Cpx), and calcic palgioclase (PI), and were sampled from Canada and Morocco.

Citation: Capriolo, M. et al. Deep CO2 in the end-Triassic Central Atlantic Magmatic Province. Nat Commun 11, 1670 (2020).

Understanding growth rings in geoduck clams and their historical environmental significance

North Pacific climate recorded in growth rings of geoduck clams: A new tool for paleoenvironmental reconstruction

Robert C. Francis, Nathan J. Mantua, Edward L. Miles, David L. Peterson

Summarized by Baron Hoffmeister

What data were used? Growth chronology (i.e growth patterns that accumulate over years in the shell of the organism, similar to tree rings) of geoduck clams (see figure 1) collected in Washington, USA were used to reconstruct sea-surface temperatures (SST) in the Strait of Juan de Fuca.  

This is an image of a geoduck. These are known to have life spans lasting over 165 years. From How Stuff Works.

Methods: This study used growth ring data in geoduck clams to determine how sea surface temperatures affected the shell growth (something called “accretion”) within these organisms over their life span. 

Results: Geoduck clams are a part of the class Bivalvia (i.e., a marine or freshwater mollusk that has its soft body compressed by a shell; this includes other organisms like snails and squids). These organisms produce their own shells, and the shells continue to grow as these organisms age (unlike organisms like mammals, who stop growing at a certain age). The shell accretion of these organisms can be observed under a microscope from samples of the shells. These are called growth lines and the spacing in between lines indicates how much new shell material the organism produced during a certain period of time (see figure 2). The growth lines of the geoduck clams found within Strait of Juan de Fuca correlated strongly with sea-surface temperatures. Researchers found that when the water was warmer, more growth was observed. This is common for a number of marine bivalves, and these proxy methods help construct a better understanding of sea surface temperatures from the past. 

The top panel is an SEM micrograph of the ring structure in a 163-year-old geoduck clam. An SEM is a scanning electron microscope that uses a focused beam of electrons that interact with the sample and produce signals that can be used to collect data about the surface composition and surface structures. The bottom panel shows the growth index (solid black line) with local air temperatures (dotted line) from 1896 to 1933. From 1900 to 1910, shell accretion correlated with warmer air temperatures.

 

Why is this study important? This study helps reconstruct environmental conditions and researchers can use this data in conjunction with other climate proxies to better understand how current climate patterns and ocean temperatures can affect marine ecosystems in the North Pacific basin.

The big picture: This study is important, not only for creating a more cohesive climate proxy database, but also indicating that shell accretion in specific marine organisms can provide important climatic data. Bivalves have a large geographic range and the data collected from these organisms through shell accretion studies can allow us to have a better understanding of historic climate conditions worldwide. 

Citation:

Francis, R. C., Mantua, N. J., Miles, E. L., & Peterson, D. L. (2004). North Pacific climate recorded in growth rings of geoduck clams: A new tool for paleoenvironmental reconstruction. Geophysical Research Letters, 31(6).

How Climate Change Impacts the Mortality Rate of Latin American Frogs

An Interaction Between Climate Change and Infectious Disease Drove Widespread Amphibian Declines

by: Jeremy M. Cohen, David J. Civitello, Matthew D. Venesky, Taegan A. McMahon, Jason R. Rohr

Summarized by: Kailey McCain

What data were used? 

This study combined laboratory experiments, field data, and climate records together to support their hypothesis that amphibians have a higher mortality (death) rate when exposed to warmer temperatures, this is known as the “thermal mismatch hypothesis”

Methods: 

Atelopus zeteki or the Panamanian Golden Frog in their natural habitat.

The laboratory experiments consisted of a temperature gradient and a temperature shift experiment. Both experiments exposed an endangered captive frog, Atelopus zeteki or the Panamanian Golden Frog, to a disease causing fungus, Batrachochytrium dendrobatidis, and measured the rate of death. The temperature gradient gradient slowly increased the temperature, while the temperature shift experiment exposed the frog to the fungus at specific temperature units: 14°C, 17°C, 23°C, or 26°C.  

The data was then compared to field data collected from the International Union for Conservation of Nature red list database to observe a real time decline in a total of 66 species of frog. The geographical range for the field data was limited to Latin America and the rate of decline was compared to historic monthly climate data.

Results:  

The results of the temperature gradient and temperature shift experiments show that mortality increased when the infected frog was exposed to higher temperatures. However, it also shows that temperature did not affect the mortality rate of the control group, the non infected frogs. As for the field data collected, the results showed that the frogs’ decline could not be correlated to precipitation nor altitude, but climate change, the thermal mismatch hypothesis clearly  predicted an increased decline of the species.

Figure A represents the data collected for the temperature gradient experiment and shows a linear decline in survival time with an increase in temperature. Figure B represents the data collected for the temperature shift experiment and shows the different temperature units plotted by the proportion alive versus time. The graph indicates that the warmest temperature has the lowest survival rate.

Why is this study important? 

This study tackles two of the largest challenges facing the modern world: climate change and disease prevalence. Some believe these issues are falsely linked, but the evidence collected in this study shows a positive correlation between disease induced death and increased temperature, both in a laboratory environment and the outside world. 

The big picture: 

While this study was isolated in geographical terms, the data collected gives researchers a look into what the future might hold for the spread of diseases in a warming world. Alone, the rising temperatures were not found to increase the rate of mortality; however, when mixed with a pathogen, a deadly combination was created and increased the rate of mortality greatly.

Citation: full citation of paper 

Cohen, J. M., Civitello, D. J., Venesky, M. D., McMahon, T. A., & Rohr, J. R. (2019). An interaction between climate change and infectious disease drove widespread amphibian declines. Global Change Biology, 3, 927. https://doi-org.ezproxy.lib.usf.edu/10.1111/gcb.14489

Examining the Morphology of Brachiopods to determine how the Late Ordovician Mass Extinction and Silurian Recovery affected long-term evolutionary trends

Effects of mass extinction and recovery dynamics on long-term evolutionary trends: a morphological study of Strophomenida (Brachiopoda) across the Late Ordovician mass extinction

by Judith A. Sclafani, Curtis R. Congreve, Andrew Z. Krug, and Mark E. Patzkowsky

Summarized by Soraya Alfred. Soraya Alfred is currently pursuing an undergraduate degree in Geology with a minor in Geographic Information Systems. She is a senior and intends to further her education by attending graduate school and then working in a Geology-related field. In her free time, she enjoys hanging out with friends and doing yoga.

What data were used? The distinct morphology of the shells of 61 species of Strophomenida (a type of extinct brachiopods) and 45 ancestor nodes, obtained from an evolutionary (phylogenetic) analysis.

Methods: Morphometric (shape differences) analysis was done through the use of principal coordinate analysis (PCO), which was used to plot the character data from the time- scaled phylogeny in morphospace. Morphospace is a type of graph used to represent the different morphologies of organisms, with different axes representing variables that define the characteristics of an organism. Twenty morphospace plots were made for the twenty set time-intervals between the early Ordovician and Devonian.

Results: When the morphospace at the time of the Ordovician mass extinction was examined, the data showed that the geometric center of the taxa that survived the extinction is similar to that of the genera that went extinct during the mass extinction. This implied that there were no specific morphologic characteristics that were targeted during the extinction event and, hence, was random. On the other hand, examination of the morphospace of the survivors of the Ordovician extinction, compared to the morphospace of the new genera that appeared in the Silurian showed that the center of mass shifted. This meant that the new taxa that emerged after the extinction filled a different region in morphospace, suggesting that origination was selective towards certain features. 

Figure showing the 20 morphospace plots for different time intervals. Members of Strophomenida occupy little morphospace in the lower Ordovician, but increase their area in morphospace during the Great Ordovician Biodiversification Event in the Darriwilian. After the mass extinction, new taxa that emerge in the Sillurian occupy the upper left half of morphospace which was previously unoccupied. The taxa that originated in the Devonian slowly become extinct into the Devonian.

Why is this study important? The Strophomenida order of brachiopods had a large geographic range, as well as a long geologic existence, making it ideal to study the repercussions of a mass extinction. As such, the results of this study can be applied to different lineages that were affected during the extinction in order to see how such events affect evolutionary history.

The big picture: Due to the fact that extinction happened randomly to taxa, a large amount of phylogenetic diversity was maintained, which made it possible for a great amount of diversification during the Silurian recovery. This diversification, however, resulted in less variability of morphology, which caused a morphological bottleneck. It is not possible to tell whether these changes were advantageous in an evolutionary sense or not, and so more has to be done to examine the true ecological effect of the Ordovician mass extinction. It was only through the examination of the characteristics of both the extinction and recovery period that we can begin to fully understand the evolutionary history of Strophomenida and similar patterns in other invertebrate taxa point to understand if this pattern was isolated or happened across multiple groups.

Citation: Sclafani, J. A., Congreve, C. R., Krug, A. Z., & Patzkowsky, M. E. (2018). Effects of mass extinction and recovery dynamics on long-term evolutionary trends: A morphological study of strophomenida (brachiopoda) across the late ordovician mass extinction. Paleobiology, 44(4), 603. Retrieved from http://ezproxy.lib.usf.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&db=edo&AN=133394289&site=eds-live

Ecological impacts of mass extinctions with data from the fossil record

Quantifying ecological impacts of mass extinctions with network analysis of fossil communities

By A. D. Muscente, Anirudh Prabhu, Hao Zhong, Ahmed Eleish, Michael B. Meyer, Peter Fox, Robert M. Hazen, and Andrew H. Knoll

Summarized by: Paul Ward. Paul Ward is a geology major at the University of South Florida. Currently, he is a senior. Once he earns his degree, he plans on taking the GIT and plans to work in the hydrology field. When he is not working on geology, he likes to go fossil hunting and cook.

What data were used: Data were collected using the Paleobiology Database on fossil occurrences, taxonomy, and diversity across mass extinction events through geologic time 

Methods: Using network theory (essentially, it means we treat fossil occurrences as complex and interconnected-like how many fossils interacted together in paleoecosystems) and the Paleontological database of fossil occurrence, taxonomy, and diversity over time, they compiled all of this data to show co-occurrence of fossils with a custom application that was made in python, a coding language. The results were then analyzed in RStudio.

Results: The data that was acquired during the project was compiled to create a record of fossilized species from the paleontological database to determine how communities are affected by ecological change. Using this dataset, it was shown how communities rise and fall during a mass extinction event (figure 1). The data that was acquired also shows the different severities on ecology of each extinction: for example, the Permo-Triassic extinction had an extremely severe negative impact on ecology, whereas other extinctions were not nearly as severe. Through the data it was also observed that the Devonian extinction importance was underestimated in the severity of the event. The data showed that it is close in severity to the K-Pg extinction event where it was previously a whole rank lower than observed in this study.

This diagram depicts the amount of diversity through geologic time; note the five mass extinctions and how they affected diversity differently. This graph is showing the “total swing” in diversity- the larger the peak, the more effect that it had on biodiversity.

Why is this study important: The significance of the data that was compiled shows us how the different taxa react to the severity of the extinction event and the selectivity that an event may have affected different communities compared to others. The data can also show us how these different extinctions affect ecological variation when compared (e.g., the Permo-Triassic had a negative impact on reef-building organisms, which when they go extinct, causes a significant ecological collapse). 

The big picture: This data analysis is important for the larger paleobiology community, due to the ability to show trends that occurred in the different geologic ages. With this, what is known about the causes of previous extinction events can show how different species react to different adverse conditions. With the example of coral ecology, we can better estimate how Earth’s ecosystems will react to climate conditions today from anthropogenic influences. 

Citation: Muscente, A. D., Prabhu, A., Zhong, H., Eleish, A., Meyer, M. B., Fox, P., Hazen, R., Knoll, A. (2018). Quantifying ecological impacts of mass extinctions with network analysis of fossil communities. Proceedings of the National Academy of Sciences of the United States, (20), 5217. https://doi-org.ezproxy.lib.usf.edu/10.1073/pnas.1719976115