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).

Mckenna Dyjak, Environmental Scientist & Geologist

Hello! My name is Mckenna Dyjak and I am in my last semester of undergrad at the University of South Florida. I am majoring in environmental science and minoring in geology. I have always been very excited by rocks and minerals as well as plants and animals. In high school, I took AP Environmental Science and realized I couldn’t picture myself doing anything other than natural sciences in college. While in college, I joined the Geology Club and realized that I loved geology as well. At that point it was too late in my college career to double major, so I decided to minor in geology instead. Since then, I have been able to go on many exciting field trips and have met amazing people that have helped further my excitement and education in geology. One of my favorite trips was for my Mineralogy, Petrology, and Geochemistry class that went to Mount Rogers in Virginia to observe rock types that would be similar to a core sample we would later study in class. Figure 1 below is a picture of me in Grayson Highlands State Park on that field trip! As you can see, my hiking boots are taped because the soles fell off. Luckily, some of my fellow classmates brought waterproof adhesive tape which saved my life.

Figure 2. University of South Florida Engineering Expo 2020 at EPC booth.

My favorite thing about being a scientist is that everyone has something that they are passionate and knowledgeable about. You can learn so many different things from different people and it is so fun seeing how excited people get about what they are most interested in. It is a great thing to be in a field where constant learning and relearning is the norm. I love to share what I know and learn from others as well. 

 As of now, I am doing an internship with the Environmental Protection Commission of Hillsborough County in the Wetlands Division. At the EPC we are in charge of protecting the resources of Hillsborough County, including the wetlands. An important part of what we do is wetland delineation (determination of precise boundaries of wetlands on the ground through field surveys) which requires a wide knowledge of wetland vegetation and hydric soils (soil which is permanently or seasonally saturated by water resulting in anaerobic conditions)! Once the wetland is delineated, permitting and mitigation (compensation for the functional loss resulting from the permitted wetland impact) can begin. Figure 2 below is a picture of me at the Engineering Expo at the University of South Florida explaining the hydrologic cycle to a younger student at the EPC booth!

Figure 3. Vibracore sampling at Whidden Bay, 2019.

Outside of environmental science, I have a passion for geology or more specifically, sedimentary geology. I have been fortunate enough to have amazing professors in my sedimentary classes and have discovered my love for it! I enjoy going on the field trips for the classes and expanding my knowledge in class during lectures. I am interested in using sedimentary rocks to interpret paleoclimate (climate prevalent at a particular time in the geological past)  and determining how past climate change affected surface environments. One really awesome field trip I got to go on was for my Sedimentary Environments class where we took core samples in Whidden Bay and Peace River. In Figure 3 I am in the water, knee deep in smelly mangrove mud, cutting the top of our core that we will eventually pull out and cap. I plan on attending graduate school in Fall of 2021 in this particular area of study.

The study and reconstruction of paleoclimate is important for our understanding of the natural variation of climate and how it is changing presently. To gather paleoclimate data, climate proxies (materials preserved in the geologic record which can be compared to what we know today) are used. I am interested in using paleosols (a stratum or soil horizon that was formed as a soil in a past geological period) as proxy data for determining paleoclimate. Sediment cores (seen in Figure 4) can also be used to determine past climate. The correlation between present day climate change and what has happened in the geologic past is crucial for our push to mitigate climate change.

Figure 4. Core sample from Figure 3.

I urge aspiring scientists to acquire as much knowledge they can about different areas of science because they are all connected! It doesn’t matter if it is from a book at the library, a video online, or in lecture. You also do not have to attend college to be a scientist; any thirst for knowledge and curiosity of the world already has you there.

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).

Kailey McCain, Interdisciplinary Natural Sciences Undergraduate

Kailey hiking in the Nantahala National Forest in December, 2019.

Hello, my name is Kailey and I’m a Junior at the University of South Florida majoring in interdisciplinary natural sciences, with an emphasis on geology, chemistry, and biology. Most people are surprised by my degree, and I get a lot of questions about the interdisciplinary aspect. As a future scientist, I believe it is critical to have an interdisciplinary approach to solve problems. Sir Francis Bacon, developer of the scientific method, urged not only scientists, but all people, to remove the lens they look at problems through and take into consideration the myriad of perspectives. To me, my degree embodies that. 

Upon graduation I plan on pursuing a PhD in ecology and evolutionary biology and my research interests are centered around dissecting the effects anthropogenic factors, or human activity, have on disease prevalence and transmission. 

What is your favorite aspect about being a scientist?

Graphic explaining the difference between primary (original research) and secondary evidence (syntheses, summaries).

Growing up, I always had an insatiable curiosity about life and our world. That curiosity has ranged from why we have an atmosphere to how human activity has caused harm, not only to our climate, but to all of ecology. I found that studying natural sciences challenges me, but rewards me by answering those questions.

Another aspect of science I love is the community that being in the sciences gives you! As a young woman, it is incredibly motivating to see such a diverse set of individuals working towards one common goal: expanding the knowledge of humankind. Before I immersed myself into the community, it was hard to see myself as a scientist. This was due to a lack of representation of female scientists; however, now I know that I can be whoever I want and I hope to show other young girls that too.

As to how I got interested in science, I originally went into college as planning on pursuing medicine,  but after taking a history of life course through the Geosciences department, my whole trajectory changed. I suddenly found myself so excited for the lecture and I started asking questions that didn’t have concrete answers, and that captivated me. I always wanted to help people and the world, and becoming a research scientist seemed to fit that more so than anything else.

How does your research and education contribute to the understanding of climate change and to the betterment of society?

By studying the ways in which human activity affects wildlife diseases, scientists are able to predict what our future world will look like, attempt to change the trajectory of diseases, and protect some of the world’s most amazing ecosystems. I also think it’s important to expand on this catch all term “human activity”. This can include, but is not limited to, deforestation, climate change, light pollutants, and habitat fragmentation. All of these actions are intertwined in how we look at protecting the world’s ecosystems, while still allowing for human development.

3D scan of Gyrodes abyssinus, which is Late Cretaceous in age (~100-66 million years ago).

What are your data, and how do you obtain them?

I am currently working on a systematic review of all the meta-analyses (I’ll explain what this means below) on Toxoplasma gondii, which is a type of parasite that is predominantly found in cats and humans. The data collected for this study is not found in the field or even the lab, but in other scientific publications, which is why we call it a meta-analysis! My job is to find all studies that are relevant and point out potential positive correlations between the data for other researchers to explore further.

I am also currently interning at a 3D visualization lab scanning paleontological collections (fig. 2)! The purpose of 3D scanning is to digitize collections that can be shared to people all over the world.The softwares utilized are Geomagic Wrap and Zbrush.

What advice do you have for aspiring scientists?

My advice to aspiring scientists is to not give up! As an undergrad, is it incredibly difficult to remove this level of perfection we place on ourselves, but it is necessary. Everyone has messed up, everyone has failed a test, and no one is perfect. Your well being and mental health is more important than any grade. 

Another piece of advice is to always try. There have been countless opportunities that I could have had, but I was too scared of rejection. At the end of the day, rejection is a part of life (especially the academic life).

 

3D Visualization Undergraduate Internship

Hey everyone! It’s Kailey, an undergraduate student at the sunny University of South Florida.

The image shows a specimen, Gyrodes abyssinus, sitting on a mesh block with a scan via geomagic wrap on the screen in the background.

I wanted to take some time and share with you guys an amazing opportunity I was given earlier this year. As any ambitious college student will tell you, internships are extremely important when it comes to choosing a career path. Not only do they grant students hands-on experience in a particular field, but also general time and knowledge in the workforce. Good internships are hard to come by, which is why I was elated when I got the opportunity to intern at the 3D visualization lab at USF! 

And yes, the lab is as cool as it sounds.

For a place where complex research happens daily, the mission of the lab is rather simple: to harness 3D scanning equipment and data processing softwares. These technological tools have been a wonderful addition to the arts, the humanities, and STEM everywhere, as it has not only supported, but completely transformed, the research in these worlds. This dynamic lab embodies the philosophy of open access research and data sharing, meaning that scientists and researchers from all over the world are able to use its different collections and visit historical sites from the comfort of their homes and offices.

This image shows the Faros arm scanner extended.

My job at the lab was to scan and process some specimens from the department of geosciences’ paleontological collection. The first step in this process is to use a laser scanner and scan my object in various positions (figure 1) using the FaroArm scanner (figure 2). This bad boy has three different joints, making the scanner move around any object seamlessly. The FaroArm also has a probe with a laser, which is essentially taking a bunch of pictures of the object and overlays them. An important note is that these “various positions” need to be easily and manually connected in a software called Geomagic Wrap; therefore, every scan must seamlessly match up like a puzzle! This was probably the most difficult thing to learn, as you not only must think more spatially, but pay close attention to the small, yet distinguable,details, like contour lines and topography (figure 3). In some cases, these small details mean the most to research scientists by showing things like predation scarring and growth lines.

This image shows a close-up shot of the contour lines and topography on the 3D model.

Once the scan is connected and we have a 3D model, the file is switched to a different software called Zbrush. This is where the fun and creative aspects come in! Zbrush allows users to fill in any holes that appear in the scan and clean up any overlapping scan data. This happens when the scans aren’t matched up properly in Geomagic. Next, we paint texture onto the model using different pictures of the fossil. Then, voila, you have a bonafide 3D model (figure 4). The model shown in figure 4 is of Gyrodes abyssinus Morton, a mollusc from the Late Cretaceous. 

I completed a total of three data scans and processes, but was cut short due to the coronavirus pandemic. While my time at the lab was short, I learned so much in terms of technical skills and problem solving. However, the most notable thing I learned was just how interdisciplinary science and research operates at the university level. Networking with archeologists, geologists, anthropologists, and so many more opened my eyes to the different fields contributing to the research world. The experiences I gained at the 3D visualization lab will follow me through my entire academic career.

This is an image of the final 3D model of Gyrodes abyssinus with coloration and texture.

You can visit https://www.usf.edu/arts-sciences/labs/access3d/ for information on the 3D lab and visit https://sketchfab.com/access3d/collections/kailey-mccain-collection to view the rest of my collection.