Microplastics Alter Plankton Poop

Microplastics alter feeding selectivity and faecal density in the copepod, Calanus helgolandicus

Rachel L. Coppock, Tamara S. Galloway, Matthew Cole, Elaine S. Fileman, Ana M. Queirós, & Penelope K. Lindeque

Summarized by Adriane Lam

The Problem: There is a growing body of research that shows that microplastics, tiny (1um-5 mm) pieces of plastics, have made their way into the deepest reaches of our oceans and are being ingested by marine life. Microplastics ingested by animals have been shown to cause adverse health effects to them, but as consumers of marine animals, these same microplastics are making their way into our diets. As yet, we do not know the exact ways in which microplastics can affect human health on longer time scales.

Zooplankton, which are small animals and protists that float in the water column and feed on primary-producing phytoplankton, are an important link between phytoplankton and other, larger animals. Zooplankton make up the base of the food chain, and are the main food source of marine mammals such as blue whales.

Different species of copepods.
Different species of copepods.

One type of zooplankton is especially common in our oceans today. Copepods are marine crustaceans that are found in nearly every freshwater and saltwater habitat. In addition to being an important food source, copepod poop is an important part of the biological pump. In other words, these animals’ poop transports atmospheric carbon dioxide (which is trapped in organic matter, or fixed carbon) to the seafloor, where it is stored in seafloor sediments.  The poop also provides important nutrients to other animals that live within or on top of these sediments. Copepods have been shown to ingest microplastics in the wild. The ingestion of microplastics by copepods may alter the way in which these animals select their food. And of course, if microplastics are being ingested, they are also being exported to the seafloor in fecal pellets. This study was designed to look at how microplastics alter how copepods choose their food and how the ingested plastic materials affect the sinking rate of copepod poop.

Methods: In this study, the scientists grew three species of microalgae (all that copepods like to feast on) in the lab and spiked it with different types of microplastics. The microplastics included things such as nylon, which is commonly found in clothing, especially active wear, and polyethylene, which is the most commonly-used plastic in the world (it is used to make shopping bags, shampoo bottles, and toys, to name a few uses).

The microalgae with microplastics was then fed to the copepods back in the lab, where the amount of microplastics ingested. The fecal pellets from the copepods were then collected and rinsed over a screen. To determine if microplastics contained in the poop affected the sinking rate of the pellets, the scientists dropped the pellets into cylinders filled with filtered seawater. They marked where the pellet was in the cylinder every 40 mm. To determine how different each pellet sank with microplastics, the scientists also measured the rate at which copepod poop without microplastics fell through the water column. When the poop reached the bottom of the cylinders, they were taken out and examined under a microscope. This way, the scientists could count the number of plastic pieces in each pellet.

Results: The scientists found that copepods preferentially liked to eat microplastics in a smaller size range (10-20 um), with a preference for the polyethylene over nylon fibers. When the copepods were exposed to microplastics, they preferentially did not eat as much algae. In addition, the copepods shifted their preference for one species of algae over others. Nylon fibers impeded ingestion of algae that was a similar size and shape to the microplastics. The scientists think the copepods associated algae of similar size and shape with microplastics, and thus avoided eating that algae species in an attempt to avoid plastic consumption.

Images of the contaminated copepod poop. Image a contains nylon fibers, image b contains polyethylene spheres, and image c contains polyethylene spheres.

The study confirmed that fecal pellets that contained both polyethylene and nylon particles were slower to sink through the water column. There was a difference in sinking rates between poop that contained more polyethylene, a denser microplastic, compared to nylon, a less dense material.

Why is this study important? This study is one of several that highlight the ways in which plastics are negatively affecting our food chain in the marine realm. The reduced sinking rate of fecal pellets may also affect the rate at which carbon dioxde, a major greenhouse gas, can be removed from the atmosphere through photosynthesizing algae who are then eaten by zooplankton. If fecal pellets are left to float for longer, there is also a higher potential of the microplastics being re-ingested by other zooplankton through coprophagy (ingestion of fecal pellets). On long and short timescales, the decreased export of poop and fixed carbon dioxide to the seafloor may have large consequences, as plastic within poop could keep more carbon from being exported and stored on the seafloor.

Citation: Coppock, R. L., Galloway, T. S., Cole, M., Fileman, E. S., Queirós, A. M., and Lindeque, P. K., 2019. Microplastics alter feeding selectivity and faecal density in the copepod, Calanus helgolandicus. Science of the Total Environment 687, 780-789. Online.

Plankton Photo Shoot Part II: Creating the Perfect Image

Adriane here-

This post is a follow-up to one I wrote previously called ‘Plankton Photo Shoot‘. In that post, I described how I take images of my fossil plankton using a scanning electron microscope, or SEM. But that was really just the first phase of taking images. In this post, I’ll talk a bit about what I do with the SEM images once I have them, and how I clean them up.

After I have SEM images, I save them to a few different folders. When taking images of fossil plankton, we usually take several pictures of the same specimen: one of the spiral side, the umbilical side (think of this as your back and front), and one of the side view of the specimen. After the images are organized into the appropriate folder that corresponds to the side of the plankton I took an image of, I then begin the editing process!

This is a screenshot of an image of a plankton species called Globorotalia tumida. Here, the image is imported into Adobe Photoshop.

The first thing I do is open the image I want to work with in Adobe Photoshop. Once imported, I then use the ‘Quick Selection’ tool to draw an outline around the fossil. I do this so I can copy and past just the image of the fossil into a new document and cut out the background. One I have the fossil isolated, then the real fun begins!

This is another screenshot of the fossil isolated from the background using the ‘Quick Selection’ tool in Photoshop.

The first thing I do with an isolated fossil image is to zoom into the image. The reason I do this is because I want to inspect the image to see how well the ‘Quick Selection’ tool worked. Sometimes, if an image does not have a lot of contrast, or the background looks the same color as the fossil, some of the background will be included in the selection. If this happens, I then use the Eraser tool to go around the outside edges of the image. This makes the image more crisp and defined!

This is what the fossil image looks like when I zoom into the image at 400x magnification. The edges already look quite good, but notice there is a small gray ‘halo’ around the image, which is especially apparent on the left side.

This is what the image looks like after using the eraser tool on the edges of the image. You can’t tell too much, if any, of a difference, but it does help give the image a bit more definition! I also delete the white background before I save the image as a .PNG file type (.PNG files don’t have a background, which is great because then I can put the image against any color background I want to later).

The final image! From here, the image is saved as a .PNG file for later use!

And that’s it! I now have a beautiful fossil image that will be used later in a publication! Of course I have to repeat this process for each fossil (which, right now, I have over 200 to edit!). Stay tuned for Part III of Plankton Photo Shoot, where I’ll show you how these images will be displayed in a publication for other scientists!

Johanna M. Resig Fellowship: Honoring a Wonderful Foraminiferal Researcher

Adriane here-

Johanna Resig’s graduation photo.

I’ve done a lot of stuff during my time here at UMass Amherst, probably too much stuff (including building this website with Jen and collaborators, which is definitely something I have no regrets about!). Because of the amount of teaching, outreach, and large research projects I’ve done and continue to do, my PhD, which is funded by my department for 4 years, will take an extra year. However, my funding runs out at the beginning of May 2019.

It’s not uncommon for a PhD degree to run over the 4 year mark; in fact, it’s really quite common. But how to sustain oneself for this extra time is the tricky part. There is money available to graduate students to support us in our final year(s) of our degree through fellowships and grants. These are often very competitive and hard to win, but totally worth applying for. So I decided to apply for a fellowship to fund the remainder of my time here at UMass.

The fellowship that I applied for is through the Cushman Foundation for Foraminiferal Research, an organization specifically for scientists who work with fossil plankton. The organization has been around for quite a while, and its members include professors, researchers, and students from all over the world. The Foundation is great because they have several grants and awards for students, to fund their research and travel to local, regional, and international meetings.

A photo of Dr. Resig and her pet cat! I was thrilled to find this photo, as I too am obsessed with foraminifera and cats!

The Johanna M. Resig Foraminiferal Research Fellowship is named after its namesake, who was a life-long foraminiferal researcher and editor of one of the most prominent journals for foraminiferal research, the aptly-named Journal of Foraminiferal Research. Johanna was born in Los Angeles, California on May 27, 1932. She  found her love for geology at the University of Southern California, where she received her Bachelor of Science in 1954 and her Master of Science in 1956. After graduation, Johanna went to work for the Allen Hancock Foundation. There, she studied foraminifera that live off the southern coast of California. In 1962, Johanna was awarded a Fullbright grant, a very prestigious award that gives money to scholars to study abroad for a few years. With this grant, Johanna continued her research at the Christian Albrechts University in Kiel, Germany. While in Germany, she earned her PhD in natural science in 1965. Once she had her doctorate, Dr. Resig began a professorship at the University of Hawai’i as a micropaleontologist in the Institute of Geophysics. She was the first woman recruited in the Hawai’i Institute of Geophysics, and remained the only one for several years. She was a professor at the university for over 40 years, where she published over 50 articles and book chapters on foraminifera. Dr. Resig published mainly on benthic foraminifera (those that live on the seafloor) as well as planktic foraminifera (those that float in the upper water column). She worked with sediments from all over the world, and also used the shells of foraminifera to construct geochemical records of our oceans. During her career, Dr. Resig described and named five new species of foraminifera and even a new Order! Dr. Resig was not only known for her research, but she was also a dedicated mentor and teacher at the University of Hawai’i. While there, she taught hundreds of undergraduate and graduate students in her courses, and mentored about a dozen graduate students. When Dr. Resig passed away on September 19, 2007, her family gave funds to the Cushman Foundation in her name, and thus the Johanna M. Resig Foraminiferal Research Fellowship was established.

Interestingly, my PhD advisor, Mark,  worked with Dr. Resig during her career. They sailed together on a large drillship called the Glomar Challenger, which took sediment cores of the seafloor for scientists to study. During an expedition together to the western equatorial Pacific (called ‘Leg 130’), they were both micropaleontologists (scientists who use tiny fossils to interpret the age of the sediments and reconstruct the ancient ocean environments). Mark is a huge fan of country music, and he recalled that he loved to play country music on the ship while the scientists were working. One song he was particularly fond of, ‘All My Exes Live in Texas’ by George Strait, was deemed entirely comical by Johanna! Mark describes Johanna as a dedicated scientists, a wonderful micropaleontologist, and someone that was a joy to be around.

A group photo of the scientists who sailed on Leg 30 in the western equatorial Pacific Ocean in 1990. Dr. Johanna Resig is circled in red.

The fellowship named after Dr. Resig will support the remainder of my time as a PhD student at University of Massachusetts Amherst. The money will be used as stipend (which is a fancy academic word for income), but it can also be used for analyses and lab expenses and travel to conferences. One way in which I’ll use the money is to pay an undergraduate student to process sediment samples that I will use in my next research project. This way, I’ll get a jump-start on my next project, and a student will be earning money doing science. They will also learn more about the samples that are collected as part of scientific ocean drilling. It’s totally a win-win situation, and I feel that by using part of the fellowship to mentor and help the next generation of students, I am honoring Dr. Resig’s memory and her commitment to mentoring and advising.

 

 

Amherst Elementary Science Night!

Solveig at the fossil table. Here, she is telling kids and parents about whale baleens. Visible on the table is a walrus vertebrae and a piece of a whale vertebrae (the large, plate-sized fossil).

Adriane here-

Recently, I participated in the first-ever Amherst Elementary Science Night. This event, held at one of the local middle schools in Amherst, Massachusetts, was designed to introduce elementary-aged children to the different areas of science. Several professors, graduate, and undergraduate students  from the University of Massachusetts Amherst attended to help out with fun activities for the kids! Several professors and students from our department also attended to teach the kids about aspects of geology. Of course, I was there to tell anyone who would listen about the wonderful world of paleontology and showcase different fossils.

The event was held in the cafeteria space of the middle school, which was divided into two areas. The first area included tables with activities and fun science stuff for the younger kids. The second area was for older kids, with more advanced science activities. Altogether, there were eight of us from the geology department who attended, with three of us (me, Solveig, and our advisor, Mark) who were in the younger section with a table full of fossils!

Helen working with kids at the core table. In front of her is an image of a sediment core.

At our fossil table, we brought specimens from the three major time periods: the Paleozoic to show people what early life looked like, the Mesozoic (or time when the dinosaurs were alive), and the Cenozoic (the time after the dinosaurs went extinct to today). Some of the awesome fossils we brought along were stromatolites (fossil cyanobacteria), brachiopods, a piece of a Triceratops dinosaur bone,  a ~350 million year old coral fossil, coprolite (fossil poop), a mammoth tooth, whale ear bone, a piece of whale baleen, and a modern coral (to compare to the fossil coral). Of course all the kids wanted to touch the dinosaur bone, and the mammoth tooth is always a big hit! But my favorite part of the night was asking kids what they thought the coprolite was. Most didn’t know, whereas other kids would throw out a guess. When I told them it was fossil poop, almost all immediately started giggling, and some even made some really funny faces! It was great fun!

In the second room, two of our UMass Geoscience professors (Bill and Julie) and three other graduate students (Helen, Hanna, and Justin) ran two other tables. Julie and Helen did an activity in which they taught kids about sediment lake cores, and the different types of sediment layers in cores that can be used to interpret Earth’s ancient climates. To do this, they rolled different-colored Play-Doh into thin layers and stacked them into bowls. The different colors represented different sediment layers on the seafloor or lake bed. The kids then took their own ‘cores’ from the Play-Doh using segments of clear plastic straws! Helen and Julie also had images of real sediment cores laid out on the tables so the kids could see what these look like.

Justin (foreground) and Bill (background) at the sandbox.

Next to Julie and Helen’s table was Bill, Hanna, and Justin. They brought along our sandbox, which we use in our classes to illustrate how faults are made. The sandbox is a bit more complex than it sounds: the box is wooden, with clear plastic sides. One side of the box has a hand crank, which will push the side of the box towards the other, thus pushing the sand in front of it. The sandbox is meant to demonstrate plate tectonics, specifically what happens when one tectonic plate moves towards another. The sand represents the upper layer of our Earth’s crust. To begin, we fill the sandbox with a neutral-colored sand, then add a thin layer of blue sand, another thin layer of neutral sand, and a second layer of blue sand. Then, when we crank the handle and the sand is pushed, it creates tiny ‘faults’ that can be seen in the sand layers. This is always a fun activity for the kids (and our students!), and is a great way to communicate how an otherwise complicated geologic phenomenon occurs.

The event only lasted about two hours, but we all interacted with several kids, their siblings, and parents! Doing outreach activities like this is always fun, and reminds me of when I was younger and excited about the natural sciences. For us scientists who do a lot of serious work, events like these are important reminders of why we love doing what we do, and share that passion with others around us.

 

Plankton Photo Shoot

The SEM I use to take images of my foraminifera. The open part is looking into the chamber, which becomes a vacuum when the machine is on and running.

Adriane here-

I do a lot of research for my PhD, and some of that research is painstaking and tedious. But some aspects of research are just downright fun! Today I’m going to talk about one of my favorite parts of my research: taking very high-resolution and close-up images of my fossil plankton, foraminifera!

Because the fossils I work with are so small (about the size of a grain of sand), we need a very unique system to take high-quality and close-up images of them. To do this, people who take images of microfossils use scanning electron microscopes, or SEM for short. An SEM uses electrons reflected off the surface of the fossils to create an image. To do this, the interior of the SEM is a vacuum, and the fossils need to be coated with a conductive material. At our university, we use platinum to coat our fossils.

A close-up image of the stub. This is after the slide was coated in platinum, thus the reason why everything looks dark grey. The copper tape at the top of the image helps to reduce charging and increase conductivity within the SEM.

The first thing I do before I can take images of my fossils is to pick out specimens that I want to photograph. These are then placed onto a small, round piece of double-sided sticky tape. The fossils are so tiny, I can fit tens onto one small piece. This sticky piece is then placed onto a glass slide. We call the fossils, tape, and glass a ‘stub’. Once all the fossils are in place, I then put the stub into a coating machine. This machine coats all the fossils with a very thin layer of platinum while in the presence of xenon gas. The entire process is very quick (about 30 minutes at most). Once the specimens are coated, they’re ready for imaging in the SEM!

The stub mounted to the stage inside the SEM.

The SEM itself is a rather large contraption, but incredibly amazing! The entire machine is operated from a computer that sits on a desk beside the SEM, so everything is pretty self-contained and right there. The first thing I do after coating is to mount the stub on the stage within the SEM. This is simple: it involves taping the stub to a metal piece, which in turn fits snugly onto the stage element of the SEM.

Once in place, I then slide the door to the SEM shut and vent the machine. Venting means I push a button on the computer, which tells the machine to begin creating a vacuum inside its chamber. This process takes about ten minutes or so.

Here, I’m  focusing on a smaller spot on the image.

After the chamber inside the SEM is under vacuum, I can then begin the process of photographing my fossils! Everything from this point forward is operated using software on a desktop computer that talks to the SEM. Just like a camera, the images have to be focused before taking the actual picture. This can be either very easy, or very tedious. There are several factors to determining how the image looks on the screen: are the levels balanced, is there charging on the fossils that’s causing a disturbance, the distance of the stub fro’m the camera, etc. There are controls on the computer program that allow the user to make changes and adjustments as necessary.

An image of one of the whole foraminifera shells. This image was taken at 198 times magnification. Remember, these shells are the size of a grain of sand, so the SEM really allows us to see all the beautiful details of the shells!

I find that the best way to focus the image is to zoom in very close to the fossil I want to photography. In this case, ‘very close’ means zooming in more than 2,000 times or more, so I’m really getting up close and personal with the fossils! I use a technique where I select a small window of the entire image, and use the tools in the program to tweak and focus the image in that smaller box. This is a faster way to focus, and when I’m happy with the results, I can apply the changes made to the small area to the entire image.

Once the settings are adjusted and correct for my fossils, I can then get through taking images pretty quickly! Each image includes a scale bar to indicate the size of the fossil and the magnification, which is helpful and necessary to include with each fossil picture. For this project, I was very interested in taking close-up images of the surface of my specimens, and also taking a side-view of the shells (quite unfortunately, this means I had to break open some foraminifera shells once placed on the stub and before coating).

This is looking at a broken piece of a foraminifera shell! Those tiny holes are where it’s spines used to be when the plankton was alive and floating in the water column.

Once all the images are taken, I can then download them onto a thumb drive  and work with them on my own computer. This involves using other photography programs such as Adobe Photoshop to crop the fossil images and place them onto a black background.

Although the process of taking SEM images of fossils is incredibly fun, it’s also vastly important for research. I will include images of all my fossils in a publication. This way, other researchers will know how I tell one species apart from another, and the different characteristics of each plankton species. Ideally, I’ll have pages and pages of fossil images, called plates, included with my publications!

 

 

 

 

How fast can life recover after a mass extinction?

Morphospace expansion paces taxonomic diversification after end Cretaceous mass extinction

Christopher M. Lowery and Andrew J. Fraass
Summarized by Adriane Lam

The Problem: There is no doubt that species today are going extinct due to human activities, such as habitat loss, climate change, and the introduction of invasive species that take over areas. For example, the Florida Panther used to range throughout the southeastern U.S., but due to humans expanding into their habitat, they now only occupy a mere 5% of their former range. Polar bears are also facing loss of their habitat due to melting ice and snow caused by human-induced warming. But if humans were to disappear tomorrow, how long would it take for Earth’s flora and fauna to bounce back to the number of species before humans were here? This is a hard question to answer, but to begin to quantify this, paleontologists can use the fossil record.

In this study, the scientists looked at the time before, during, and after the end-Cretaceous mass extinction event that took place ~66 million years ago. This was one of the largest mass extinction events in Earth’s history, where about 75% of all species on Earth went extinct, including the non-avian dinosaurs. It is also an important mass extinction event to study because the event that wiped out all those species was very rapid. During other mass extinction events in Earth’s history, the extinction events themselves took on the order of millions to hundreds of thousands of years (read more about extinctions here).

An overly-dramatic image of dinosaurs during the end-Cretaceous mass extinction about 66 million years ago.

The rate at which humans are altering the Earth today is unprecedented to any climate change event in the geologic past (see our ‘CO2: Past, Present, & Future’ page for more details). Thus, scientists need to compare the rate at which we are losing species today under a very fast climate change scenario to another event that was also very fast. Therefore, studying the end-Cretaceous mass extinction is particularly valuable: it was a very quick event and one that is most comparable to the rate at which we are losing species today.

Data Used: In this study, the scientists used the fossil record of planktic foraminifera to see how long it took for life to recovered after a mass extinction event, the end-Cretaceous mass extinction. Planktic foraminifera are single-celled protists (not animals) that live in open-marine environments. They have occupied our oceans for the past ~165 million years. These protists produce a calcium carbonate (same material seashells are made of) shell, or “test,” that grows to be about the size of a grain of sand. When the foraminifera die, its shell sinks to the seafloor. Over millions of years, these shells are preserved at the bottom of the ocean. Making the fossil record of planktic foraminifera an archive of extinction and evolution events for the past 165 million years of Earth’s history! The scientists who conducted this study used this amazing fossil archive to see how long it took these marine protists to return to pre-extinction levels after the end-Cretaceous mass extinction.

Figure 1. The number of planktic foraminifera species (=diversity estimate) from 80 million years ago to 50 million years ago. The end-Cretaceous mass extinction occurred at the end of the Cretaceous, and can be identified by the major drop in diversity at this time. ‘Throw back’ indicates species that survived the mass extinction event and gave rise to new species; ‘Spinose’ indicates species of foraminifera that evolved to have spines; and ‘Symbiont bearing’ indicates species that have photosymbionts (algae that live on the spines of certain foraminifera).

Methods: As part of his master’s project, Andy Fraass compiled a database of first and last occurrences of planktic foraminifera species. First and last occurrence datums are often used in paleontology to examine how long in geologic time a species existed. The authors used these data to examine when planktic foraminifera species evolved and went extinct (Figure 1).

This dataset collected, but left unpublished until this paper, also included measurements of the species’ tests, such as the number of chambers in the shell, how quickly the chambers expanded from the earliest chamber to the last, etc. From these measurements, the authors calculated test complexity. This is a metric that shows how ‘complex’ planktic foraminifera shells became through time. For example, a species with a simple shell might have simple chambers arranged in a spiral pattern. A more complex species might have a more extreme test (Figure 2).  The test complexity of each species was then given a score, with 1 being the simplest, and 4 being the most complex or extreme.

In foraminifera, the shape of the test can be assumed to have some sort of relationship to the organism’s life strategy, or its niche, basically. A species’ niche is where and how it can live and interact with the environment. For example, humans occupy a broad range of niches: our technology allows us to live in very hot to very cold climates. On the other hand, polar bears have a very narrow niche. These animals only live in the tundra biome in the Northern Hemisphere on the ice and hunt seals. A specific foraminifera might only live at a particular depth in the ocean, or in water that’s above or below a certain temperature, or in regions with a certain abundance of food, etc. These niches are the scaffolding on which species diversity is built.

During a mass extinction event niche spaces are often completely disrupted or destroyed along with the species that occupy them. Thus, paleontologists have hypothesized that after an extinction event, the number of species cannot simply bounce back to what it was before, but the number and size of niche spaces has to be rebuilt first. This may cause the observed delay in the recovery of species after mass extinction events. This paper provided the first test of that hypothesis with real data.

Figure 2. Some examples of a morphologically simple (images A and B) and complex (images C and D) planktic foraminifera. For the simple forms, A is Muricohedbergella monmouthensis, B is Muricohedbergella holmdelensis. Notice that these shell are very simple, with chambers added to the test in a spiral pattern. The complex forms include C, Hantkenina alabamensis and D, Morozovella velascoensis. Both of these species start out with smaller chambers in their shells, with larger and more complex shaped chambers added. In addition, Hantkenina alabamensis (C) also has very prominent spines that jut out of the test. All images from pforams @ mikrotax.

Because the shape and characteristics of a planktic foraminifera’s shell is related to its niche, the authors used average test complexity of all the foraminifera that were alive at different points in time to reconstruct how many niches were occupied by forams before and after the end-Cretaceous mass extinction. Higher average complexity suggests a wider variety of niches were occupied, while lower complexity suggests that fewer niches existed.

Results: The authors found that there was a huge drop in the number of species after the end-Cretaceous mass extinction (Figure 1), which was not a surprise and something we have know about for a while. But the other finding was that along with a huge drop in the number of species was also a huge drop in the test complexity (Figure 3). It took about 5 million years for test complexity to reach the levels it was at before the mass extinction event. That’s a really long time!

Figure 3. The results of the test complexity index (TCI) plotted against time. The horizontal black lines indicate how long each planktic foraminifera species lived through time, and their position on the y-axis (TCI) indicates how complex their test was. The red line is the median of this data, and the black line is the mean. At the end-Cretaceous mass extinction, both the red and black lines drop, but then begin to increase slowly. It takes about 5 million years for TCI to increase to pre-extinction levels.

Another interesting find is that test complexity increased before species diversified. That is, new niches were created faster than new species to fill them after the mass extinction event. This study shows that before a lot of new species can evolve, there need to be a few species that evolve and open new niche spaces first.

Why is this study important? Today, humans are having a huge effect on the ability of species to survive on our planet. Through destruction of species’ habitats and niche space, we are pushing more and more species to the brink of extinction. Importantly, there are also thousands of species that have already gone extinct from human activities (such as the Tasmanian Tiger, Passenger Pigeon, Sea Mink, Caribbean Monk Seal, Quagga, Elephant Bird, Haast’s Eagle, and many more). If we keep causing animals to go extinct, we may see a loss of biodiversity that rivals those of mass extinctions that have taken place in the geologic past. But until now, we didn’t really know how long it took for new niche spaces to be filled and how that would affect how fast new species can fill those niche spaces.

This study gives us a clue: it may take as long as 5 million years after a mass extinction event for new niche spaces to be created. It then takes additional five million years for diversity, or the number of species, to rebound to pre-extinction levels. The bottom line is that it takes 10 million years for the biosphere to recover from a mass extinction event. This means that even though humans have been on Earth for a very short period of time (geologically speaking), we will have a huge impact on the flora and fauna, even if we were to disappear tomorrow.

Citation: Lowery, C. M., and Fraass, A. J., 2019. Morphospace expansion paces taxonomic diversification after end Cretaceous mass extinction. Nature Ecology & Evolution https://doi.org/10.1038/s41559-019-0835-0

Additional News Coverage:

 

A Rare and Exciting Fossil Deposit Causes Excitement and Contention in the Paleontological Community

A seismically induced onshore surge deposit at the KPg boundary, North Dakota

Robert A. DePalma, Jan Smit, David A. Burnham, Klaudia Kuiper, Phillip L. Manning, Anton Oleinik, Peter Larson, Florentin J. Maurrasse, Johan Vellekoop, Mark A. Richards, Loren Gurche, and Walter Alvarez

Summarized by Jen Bauer, Maggie Limbeck, and Adriane Lam, who also comment on the controversy below

What data were used?

Data used in this study were identified from a new site, which the authors call Tanis (named after the ancient Egyptian city in the Nile River Delta), in the layers of rocks called the Hell Creek Formation. This formation is famous amongst paleontologists because it contains lots of dinosaur fossils from the late Cretaceous (about 66 million years ago). In this study, scientists found a new layer of fossils within the Hell Creek Formation that is unlike anything paleontologists have seen before. Those who found the site examined the rock’s features and fossils, which includes densely packed fish fossils and ejecta from the Chicxulub meteoric impact. The Chicxulub impact is what caused the dinosaurs to go extinct, and finding a layer of rock that was deposited minutes to hours after the impactor struck Earth is a very rare and exciting find.

Methods

This study included a variety of approaches. The rock features (called sedimentology) and fossil features of the Tanis area and event deposit are described to determine what caused this deposit in the first place. The authors also identified other pieces of evidence to aid in better understanding the situation at hand. Ejecta deposits were described as well, in comparison to ejecta deposits that are found closer to the impact site in the Yucatan Peninsula, Mexico.

Results

Figure 1. The extremely well preserved fossils from the Tanis site. (A) Shows a partially prepared plaster jacket with partially prepared fossil freshwater fish. Next to an ammonite shell with mother of pearl preservation (that’s the pretty iridescent part that is enlarged). (B) Shows how the large amount of specimens were oriented in the rock and the inferred direction of flow estimated from the rock and fossils at the site. (C) Photograph taken in the field showing the tightly packed fish, fossilized in a clear orientation. This is figure 7 in the paper, click here to see the other figures.

Much of the sedimentology can be related to other aspects of the Hell Creek Formation in southwestern North Dakota that is an ancient river deposit that has some marine influence. In the Cretaceous period, central North America’s topography was very low which allowed for a seaway to form. This was called the Western Interior Seaway, and was home to a diverse number of animals such as plesiosaurs, mososaurs, large sharks, and ammonites. Several rivers likely drained into the Western Interior Seaway, much like the Mississippi River drains into the Gulf of Mexico today.

From studying the characteristics of the rocks within the Tanis site, the authors of the study concluded that this site was part of one of the rivers that drained into the Western Interior Seaway long ago. When the impactor struck Earth in the Yucatan Peninsula, it send huge waves (tsunamis) into the Western Interior Seaway and into the rivers that drained into the seaway. These huge waves pushed fish, ammonites, and other creatures into the seaway and into the rivers. The Tanis site is one such place where these animals that were pushed into the rivers were deposited and preserved. But not only were marine animals preserved at the site, but also land plants, such as tree limbs and flowers.

The fossils found in the Tanis deposits are all oriented in the same direction, indicating that they have been aligned by flowing water. The abundance and remarkable preservation of these fossil fishes and tree limbs suggest a very rapid burial event (the best preserved fossils are often the ones that experience very quick burial after death). The orientation of the fossils at the site along with the mix of marine and terrestrial life further supports that these fossils were deposited from very large waves from the asteroid impact disturbed this region.

Within the Tanis deposit there are also ejecta spherules, microkrystites, shocked minerals, and unaltered impact-melt glass. These are features that are commonly associated with the Chicxulub Impactor. When the impactor struck Earth, it was so hot it melted the underlying rock, sending tiny bits of molten rock into the atmosphere. These bits of molten rock quickly cooled and eventually fell back down to Earth, where today they are found all over the world. Today, these ejecta spherules and impact melt-glass all mark the huge end-Cretaceous mass extinction event that occurred 66 million years ago.

Why is this study important?

The Cretaceous-Paleogene (K/Pg) extinction event is one of the ‘Big Five’ mass extinction events (click here to read more about extinction). Like many extinction events, it is often difficult to determine the specific causes of mass destruction. However, the K/Pg extinction event is unique because scientists have many lines of evidence that a huge impactor struck Earth, sending clouds of ash and gas into Earth’s atmosphere. The new Tanis site that the authors uncovered preserves a snapshot into this catastrophic event.

This finding is very important because scientists know better understand what happened directly after the impactor hit Earth. In addition, several new species of fish have been discovered at the Tanis site, which will be important for additional studies about fish evolution through time.

Citation:

DePalma, R.A., Smit, J., Burnham, D.A., Kuiper, K., Manning, P.L., Oleinik, A., Larson, P., Maurrasse, F.J., Vellekoop, J., Richards, M.A., Gurche, L., and Alvarez, W. 2019. A seismically induced onshore surge deposit at the KPg boundary, North Dakota. Proceedings of the National Academy of Sciences (PNAS), doi: 10.1073/pnas.1817407116

What’s all the commotion about?

It’s not every day that paleontologists make the national news, but this paper and the article written about it in the New Yorker (click here) caused a lot of commotion within the paleontological world. This is a great and potentially groundbreaking find, however, what caused the commotion was the sensationalist attitude of the New Yorker piece that left a lot of paleontologists uncomfortable. So what’s the big deal here? We break down a few (not all) of the issues with this article:

1. Breaking of Embargo

Although the published study is very exciting and will add greatly to our knowledge about the end-Cretaceous mass extinction event, the media hype around the study was handled very poorly for several reasons. All published studies go through peer review. This is when a paper is sent out to multiple other scientists who read the article and make sure that it is scientifically sound and is a good piece of science based upon other good science. During this waiting period while the paper is going through peer review or being finalized with publishers, the authors should avoid talking with popular media or publicizing their paper. When publishing in academia there is a period of time (embargo) where access to the findings of a paper is not allowed to the public. This is for a variety of reasons, having to do with copyright transfer, finances to support the journal or publisher, and more.

The New Yorker press article was released almost an entire week before being available for the community to examine. This means that the embargo was violated.

The reason embargos exist is to give journalists and the researchers they talk to some time to look at fresh findings and determine what the story is, whether it’s worth telling, and if there’s anything suspicious about what’s presented. – Riley Black (Slate article)

2. Paleontologists as Rough-and-Tough Dudes (and Unusual Folks)

The New Yorker article was also controversial because it framed paleontologists as belonging to a narrow demographic (read: white men who love the outdoors). Not all of us in paleontology are men, not all of us are white, and not all of us came into geology loving the outdoors (see the great diversity of folks working in paleontology on our ‘Meet the Scientist’ blog). Paleontologists have had to work very hard to break through the stereotypical conception of what we do and who we are, and this article did not help to address the great diversity of scientists working in the field of paleontology.

In addition, the New Yorker article only quoted and interviewed other male scientists, many of whom have been working in the field for decades. The article left out the voices of women and early-career researchers who have made valuable contributions to the field of paleontology. For more on this, read the Slate article by science writer, Riley Black “It’s Time for the Heroic Male Paleontologist Trope to Go Extinct”.

This article also reinforces the “lone-wolf” stereotype of geologists and paleontologists-a man going out west, few to no other people around, and spending his days looking for paleontological treasure. This image is perpetuated through the article because the author chose to continually highlight the privacy and secrecy asked by the De Palma. While this is certainly an attitude held by some paleontologists, the reality is that the majority of us work in teams. Time Scavengers is run by a large team of people and so is our research! Like working in any field, we all have our strengths and better science happens when we invite people to work with us who have different strengths and can help us.

Lastly, the article frames paleontologists in a not-so-flattering light. In one paragraph, the article states “…I thought that he was likely exaggerating, or that he might even be crazy. (Paleontology has more than its share of unusual people).” Firstly, what does unusual even mean? The STEM (Science, Technology, Engineering, Maths) fields are full of intelligent, diverse, and colorful folks from all walks of life. To imply that any one branch of science has ‘its share of unusual people’ is unfair and regressive.

3. Dinosaurs as the Star of the Show

Paleontology is not just diverse in terms of the people who work in the field, but also in terms of the different types of life that we work with. For example, our Time Scavengers team, we have folks who work with fossil plankton and echinoderms. In fact, most paleontologists work with invertebrates- animals that do not have backbones, or any bones at all. Some of the most foundational findings in paleontology are based on the fossil record of invertebrates and early vertebrates. Regardless, most of the public’s fascination lies with dinosaurs (we understand, they were gigantic, ferocious, and unlike anything that’s alive today).

However, this fascination with dinosaurs can lead to over exaggeration of studies and sensationalizing, which is exactly what happened with this article. The published study of the Tanis site only mentions one dinosaur bone out of all the fossils found. The real story here is about the wonderful assortment of fish, tree, and flower fossils, some of which are completely new to paleontologists.

Another article by Riley Black that gives more of a spotlight to the amazing fish found at the locality, “Fossil Site May Capture the Dinosaur-Killing Impact, but It’s Only the Beginning of the Story.”

Dr. Steve Bursatte, Paleontologist at University of Edinburgh commented on both the New Yorker article and the PNAS article on his Twitter account, click here to read more. He comments on the broken embargo and how the New Yorker article sensationalized the ‘dinosaur’ side of the story.

4. Proper Handling of Museum-Quality Specimens

The article that was published in the New Yorker raised a lot of concerns within the paleontology community regarding the handling and storage of the fossils that were found at the Tanis site. It is clear from the article that DePalma had a bad experience early on with fossils that he had loaned a museum not being returned to him, however, by maintaining control over the management of his specimens, it undermines those people working in museums who have degrees and years of experience handling fossil and other specimen collections. Anyone who has borrowed specimens from a museum knows the immense amount of paperwork that goes in on all ends to make sure the specimens leave a well documented trail.

Jess Miller-Camp, Paleontology Collections Manager and Digitization Project Coordinator at Indiana University commented on the New Yorker article and addressed her concerns as a museum professional, click here to read her Twitter thread. She comments on the process of loaning specimens to and from museums and proper ettiqute. Read her thread to learn more about this and why museums should be asked to comment.

In 1997, a T. rex nicknamed Sue was sold at a Sotheby’s auction, to the Field Museum of Natural History, in Chicago, for more than $8.3 million.

This quote is misleading. No museum would have adequate funds to secure Sue. The California State University system, Walt Disney Parks and Resorts, McDonald’s, Ronald McDonald House Charities, and other individual donors aided in purchasing Sue for the Field Museum. The Field Museum rallied resources to ensure this valuable specimen remained in a public institution.

In addition to proper storage and archiving of fossils, one of the key tenets of any kind of scientific research is reproducibility– how well can other scientists replicate the results that you got. In paleontology, being able to look at the exact same fossils that another scientists looked at is a key part to reproducibility, as well as allowing the science of paleontology to advance. Whenever a paleontologist finds something they think is “new” to science, or is a really important find (special preservation, currently undocumented here, etc.) if you want to publish a paper on that fossil, the fossil needs to be placed in a public institution like a museum or a similarly accredited fossil repository. This way, future scientists are able to track down that fossil you published on and continue working on understanding it, or using it in other studies. Keeping fossils that are published on in museums is also critical because it ensures that that fossil has a safe place to be stored after being worked on and is less likely to be lost in an office or lab space!

5. Respecting the Land and Indigenous People

In the field of paleontology, people, who are more often than not white, venture into another country or a part of the ‘wilderness’ to find fossils and sites that are completely new and never-before-discovered or seen. These lands that contain fossils were owned by indigenous people long before Europeans arrived in North America, and were likely known about centuries before. Often, when sensational popular science paleontology articles are published, the authors leave out the voices of indigenous people and respect for their land. In the New Yorker article, there was no mention of the indigenous people that lived in the Dakotas, or how their ancestors perceived the dinosaur and fish fossils in the area. To frame amazing paleontological finds as being in desolate wastelands is harmful and erases the narratives of people who have lived in these lands for centuries.

For a more thorough discussion on this topic, click here to read the Twitter thread by Dr. Katherine Crocker.

 

Click here to read a article written by Dr. Roy Plotnick in Medium that also summarizes the issues and causes of commotion surrounding this astounding find.

Teaching Science Communication to Biology students

Adriane here-

This semester, I was given the opportunity to do something new: lecture to an undergraduate Biology writing class about how to communicate science to non-scientists! I was invited to speak to this class because the professor knew about my education outreach and blogging experiences with Time Scavengers.

One assignments the class had to do was summarize a published scientific paper for the general public. So I thought it would be a good idea to put together a short slide show for the students about who I am, how I got involved in science communication, and an overview of Time Scavengers. I also told the students about some of the lessons I’ve learned as a science communicator, and some best practices. Although there are several tips and tricks for writing for the general public, here are the four I chose to focus on:

  • Science writing for the public should be the opposite of formal scientific paper.
  • Explain figures in the figure caption, even if it is repetitive with the text
  • Use figures that are simple, labeled, and not too overwhelming
  • Reduce the jargon- include explanations and define any jargon words that are used
The students working on their summaries.

The paper the students summarized was about the amount of microplastics, or very small pieces of plastics, that are found in the southern part of the Marianas Trench. The paper and it’s findings are very important because it highlights the fact that our plastic waste is making it into the farthest reaches of our oceans, into the food chain, and affecting our wildlife. So it was a great paper for the undergrads to practice their science communication skills. There was only one catch: they could only use the ‘ten hundred’ most common words from the English language to write their summaries, thus ensuring they couldn’t use any science jargon words. This was done on the Up-Goer Five Text Editor, which allows you to type text directly into a word box, but notifies you if you use a word that is not part of the 1,000 most common words.

When we began the activity, the students were a bit frustrated at first, as words such as ‘ocean’, ‘Earth’, and ‘salt’ aren’t words they could use! But then, they got creative and began coming up with ways to explain some of the more difficult concepts!

Needless to say, this was a really fun activity that resulted in quite a few laughs! I was impressed at how well the students’ summaries really captured the messages in the paper they were summarizing. This activity really highlighted the fact that we (scientists) don’t have to use large jargon-y words to get across important messages!

Below are some of the students’ summaries:

“Lots of small pieces of things you would find all around you are in deep water where they are hurting animals. Deep water animals are hurt when they eat things that they should not eat. People put these man made things in the water and they break down into small pieces that shouldn’t be eaten. There are lots of different things that can break down, and they’re in bags, computers, phones, clothes, and food packs in stores. The small pieces are all around the animals, and they are eating them all the time. People are worried and are finding lots of truth saying that this is going to make the animals die and hurt how they act with each other and what they eat. It also makes them sick because they can’t get bad things in their body out, and can’t make important things that help the brain and body talk to each other. People lost a lot of the bad things that are in the water, and we have now found them in the really deep water, and it is hurting animals in both deep and upper water now.”

“The fine pieces thrown away by human after using are getting into the deep water and hurting the animals that live in the deep water. Many kinds of these used pieces are found in different places of the water, even in the deepest part. This is because that the pieces on the top of the water would go deeper when the land shakes or water moves. Studying these piece can help us better understand them and clean them from the water, keeping animals save in their home.”

“Humans use a lot of stuff that eventually finds its way into the water. These small pieces of stuff start on land and eventually move to the water where it takes a lot of time to break down. Eventually this bad human stuff finds it’s way to the deep parts of the water where it is not supposed to be. Animals living in the water can easily be hurt and get sick by this bad human stuff. With this stuff in the water it will be very hard to take away. In order to keep a lot of life, humans must do something to clean the water. Clean water will help human life as well.”

“We studied problems in bodies of water like bad things on the ground under water. Further down we go, more build up of the bad things is seen. The deeper down in the water, the worse the problem is. Many pieces of bottles and other man made things sit and bother surrounding life. Another problem that was presented in the reading was the ground taking in the man made things-which makes it harder for animals to eat, breathe, and live. The changes that have happened because of the man made things are still not known and being looked into.”

“A big problem that is growing is making the bodies of water, and what lives there, sick. These bad things are small and can be found more in deep water. Humans are bad because they are not safe with throwing away these things so it hurts water animals by making them sick. The well-being of water and animals needs to be helped by humans. Cleaning up water is good, as well as watching what is put into water to stop the problem before it happens. Water is very important to human and animal life, so bad things being put into bodies of water needs to stop. ”

“Lots of small pieces of things you would find all around you are in deep water where they are hurting animals. Deep water animals are hurt when they eat things that they should not eat. People put these man made things in the water and they break down into small pieces that shouldn’t be eaten. There are lots of different things that can break down, and they’re in bags, computers, phones, clothes, and food packs in stores. The small pieces are all around the animals, and they are eating them all the time. People are worried and are finding lots of truth saying that this is going to make the animals die and hurt how they act with each other and what they eat. It also makes them sick because they can’t get bad things in their body out, and can’t make important things that help the brain and body talk to each other. People lost a lot of the bad things that are in the water, and we have now found them in the really deep water, and it is hurting animals in both deep and upper water now.”

Humans placed too many bad things like bags and bottles in the deep water. This, in the end, hurts the tiny animals living in the water. If this goes on, it will even hurt our entire home later on. We first thought that the bad things were only near the top of the water, however it seems that the bad things are even in the deepest parts of the water as well. The people who study this are explaining how they found this out in this paper.

Preparing Samples for Stable Isotopic Measurements

Adriane here-

Recently, Andy and I have started to collaborate on a research project together. Well, the project is his, and I’ve agreed to do some lab analyses for him in exchange for being a co-author on the research paper. Being a co-author means that on a published journal article, I will have my name as one of the people who contributed to the science in the paper. My job for this project is to pick, weigh, and analyze foraminifera for stable isotope analyses. In this post, I’ll go over briefly how I do this!

Lucky for me, Andy had already picked the foraminifera he wanted to be analyzed from his sediment samples and put these into cardboard trays. Each tray is labeled so that it corresponds with the sediment sample from which it came, thus I know exactly which sample I’m working with. The first step is to take the cardboard tray and put it under the microscope. Using a paintbrush with water, I gently pick up the foraminifera specimens and place them in an aluminum tray. After I’ve filled up all 14 of my aluminum trays, I take these and weigh them on a microbalance, which is a fancy name for a scale that measures very small weights (in this case, micrograms). I want the samples to weigh between 180 to 220 micrograms, as this is the ideal mass needed to get a good measurement. After the samples are weighed, I then put them into a tall glass vial that is numbered. I have a spreadsheet on my computer where I keep track of which sample is in which vial.

The home-made device we use to pump helium into the vials and air out. We fill 10 vials at a time for about 4-5 minutes each.

After I have about 60-80 vials of weighed foraminifera, I can then begin the process of analyzing them for stable isotope measurements. In this case, we want to measure carbon and oxygen (see our ‘Isotopes‘ and ‘Carbon & Oxygen Isotopes‘ page for more details on what these data are used for). This process is a bit tedious and always makes me nervous, but it’s also kind of fun!

The acid is poured into a syringe with a needle, and then four drops of acid are inserted into each vial. It’s a very medical-like procedure for a geologic endeavor!

Analyzing foraminifera for stable isotopes means working with a mass spectrometer, a (very expensive) machine that, very simply put, measures the amount of carbon and oxygen that are within a gas. Notice that the mass spectrometer needs a gas, not a solid, to be able to take a measurement. This is where things get fun! The first step is to make sure all of the air is out of the glass vials. To work correctly, the mass spectrometer has helium constantly being pumped through it. No air is allowed into the system, as air contains oxygen, and oxygen is one of the elements we want to measure. If air gets into the mass spectrometer or into the vials, it’ll ruin the results of the analyses. To rid the vials of air, I put the vials on a contraption that continually pushes helium into the vials through one tube while letting air out of another small tube. I let the vials fill with helium for about 4 minutes each. After the vials are filled with helium, I then put acid into each vial. Four drops of 100% pure phosphoric acid is placed into each vial. This is done to turn the foraminifera, which are made of calcium carbonate, into gas (any acid placed on calcium carbonate, the material which seashells and foraminifera are made of, will cause them to dissolve). Because calcium carbonate is CaCO3, the resulting gas includes elements of both C (carbon) and O (oxygen).

Once all the vials are filled with acid, it’s then time to start the mass spectrometer! This is a very easy process considering the machine itself is complex and intimidating (well, at least to me). In short, I basically change the file names, make sure the machine knows how many samples its analyzing, and then I click the ‘Start’ button. Each sample takes ~12 minutes to analyze, so an entire run of 60 to 80 samples takes about 12 to 16 hours.

The last part of this process will be to take the results, put them into a spreadsheet, and give them to Andy. From there, Andy will have the hard but fun job of interpreting the data and writing the majority of the research paper (with help from us, when needed).

Antarctica’s Ice Sheet Sensitivity to Warming 23 to 14 Million Years Ago

Antarctic ice sheet sensitivity to atmospheric CO2 variations in the early to mid-Miocene

Richard LevyDavid HarwoodFabio FlorindoFrancesca SangiorgiRobert TripatiHilmar von EynattenEdward GassonGerhard KuhnAradhna TripatiRobert DeContoChristopher FieldingBrad FieldNicholas GolledgeRobert McKayTimothy NaishMatthew OlneyDavid PollardStefan SchoutenFranco TalaricoSophie WarnyVeronica WillmottGary ActonKurt PanterTimothy PaulsenMarco Taviani, and SMS Science Team

The Problem: The early to mid-Miocene (23 to 14 million years ago) is an interval of geologic time where atmospheric carbon dioxide (CO2) concentrations (about 280 to 500 parts per million) were similar to those that are projected for the coming decades under human-induced climate change. Thus, this interval of time is interesting for geologists because we can use the geologic record from this time to interpret how our oceans, atmosphere, and ice sheets ‘behave’ under warming scenarios. Understanding the extent to which the Earth will warm, weather patterns will change, and sea levels will rise in the coming decades can help scientists, the public, and policy makers prepare for our future. Related to sea level rises is understanding how much continental ice sheets, such as those on Greenland and Antarctica, will melt.

Map of Antarctica with a red dot denoting where the ANDRILL core was drilled.

In this study, geologists use several methods to determine how sensitive Antarctic ice sheets are to increases in atmospheric CO2 concentrations 23 to 14 million years ago. The results from this study are useful in that we can determine how much Antarctic ice may melt in the coming decades, which would add to sea level rise.

Methods: To interpret how sensitive Antarctic ice is to atmospheric warming (or increased average global warming), the scientists use sediments obtained in a drilled core from the coastal margin of Antarctica (an ideal location to study the melting and growth of ice sheets). The core was drilled in 2006 and 2007 as part of the ANDRILL (ANtarctic DRILLing Project) scientific drilling project from the McMurdo sector of Antarctica. The core is approximately 1,138 meters long, and contain sediments that are dated at over 20 million years old!

This study is very unique and fun because the scientists use several proxies (or naturally-occurring records) to interpret what the margin of Antarctica looked like through time. The presence and abundance (or numbers) of plankton (such as foraminifera) and pollen grains indicate when the margin of Antarctica was warmer, and ice sheets had melted back. For example, when the ice around Antarctica melted back, this allowed more room and soil for plants to grow. The lithology, or general characteristics of the sediments and rocks collected in the ANDRILL core, was also used as a clue to the changing environment of Antarctica through the study interval. Just knowing the different sediment types through time is a very powerful proxy itself!

Results: Using all the different methods and proxies, the geologists were able to interpret how Antarctic ice sheets melted and re-grew through the Miocene interval. They determined that several times from 23 to 14 million years ago, ice grew and retreated inland. They found that Antarctic ice becomes very sensitive to small changes in the amount of carbon dioxide in the atmosphere.

Four environmental motifs as defined by the authors of the study. The location of the ANDRILL core used in the study (A2A) is noted in each image. Notice how the ice sheet retreats from I to IV as the amount of carbon dioxide in the atmosphere increases through time.

To best illustrate their findings, the authors of this study created four ‘environmental motifs’. These are images of what the scientists think the Antarctic margin looked like through time. Note that there are only four motifs; these just capture the major environments that the scientists inferred from their data. There were likely other ‘in-between’ environments. But notice how dynamic the ice sheet around the Antarctic margin were: the ice melted and then re-grew quite a bit in response to warming and cooling events through the Miocene!

Why is this study important? This study highlights and solidifies the hypothesis that Antarctic ice sheets were very sensitive to changes in atmospheric carbon dioxide concentrations during the Miocene. The findings of the study also indicate that Antarctic ice will behave similarly under increased warming predicted for Earth’s future. Melting ice will have a huge impact on sea level, which will make living on coastal lands hard or impossible due to flooding.

Citation: Levy, R. H., Harwood, D., Florindo, F., Sangiorgio, F., Tripati, R., von Eynatten, H., Gasson, E., Kuhn, G., Tripati, A., DeConto, R., Fielding, C., Field, B., Golledge, N., McKay, R.,, Naish, T., Olney, M., Pollard, D., Schouten, S., Talarico, F., Warny, S., Willmott, V., Acton, G., Panter, K., Paulsen, T., Taviani, M., and the SMS Science Team, 2016. Antarctic ice sheet sensitivity to atmospheric CO2 variations in the early to mid-Miocene. PNAS 113(13), 3453-3458. doi: 10.1073/pnas.1516030113.