Fossilized Mollusks used to determine Cenozoic climate and elevation of the Himalayan-Tibetan Plateau

Clumped isotope thermometry of modern and fossil snail shells from the Himalayan-Tibetan Plateau: Implications for paleoclimate and Paleo-elevation reconstruction

Yang Wang, Benjamin Passey, Rupsa Roy, Tao Deng, Shijun Jiang, Chance Hannold, Xiaoming Wang, Eric Lochner, and Aradhna Tripati

Summarized by Brynn Crocker, pursuing a master’s in teaching at Binghamton University with a bachelors in Geology. 

What data were used: Both fossilized and modern aragonite mollusk shells were collected from seven different lakes within the Tibetan Plateau. The fossils collected from these sites were dated to be of Cenozoic age. Clumps of carbon 13 and oxygen 18 (isotopes of carbon and oxygen) were measured to determine paleo-temperatures. The formation of the Himalayan Mountains is thought to have had a large impact on the regional climate during the time. Mollusk fossils are great archives for determining paleoclimate.

Methods: This study used X-ray diffraction to determine the values of C13 and 18O bonds (clumps) within the shells. These clumps help determine paleo temperatures and elevations. Modern shells both alive and dead were collected from the lakes in the Tibetan Plateau. The fossil mollusks were collected from fine grained sandstone, indicating that they were not transported there but lived in the freshwater lakes. These shells were then analyzed to find their clump values, which were then compared to modern temperatures. Intact Cenozoic fossil shells were then collected and analyzed to find their clump values. Intact shells were used to avoid using shells that have gone through any diagenetic alteration (changes to the fossils through heat,  pressure, and chemistry). Shells that contain calcite indicate diagenesis. Trace amounts of calcite yield temperatures of an average ~10º C lower than those with no calcite from the same strata. Shells were cleaned using HCl (hydrochloric acid) solution and then rinsed with distilled water. Modern shells were soaked in 30% H2O2 (hydrogen peroxide) to remove any organic matter. The isotope clump data was reduced using both the Henkes calibration and the Eagle calibration.

Black and white map showing the location of the study areas.
This figure shows the region of study and the basins within the area.

 

Results: After analyzing the 13C-18O clumps it was determined that southwest Tibet was warmer 4-5 Ma than today and paleo-elevation was similar to today. Using the Henkes calibration of temperatures calculated from the clump values, the temperature of the Himalayan-Tibetan Plateau ranges from 1ºC to 17ºC, with a mean of 10ºC. Using Eagles calibration, the temperature values range from 8ºC to 21ºC, averaging 16ºC. The Henkes calibration is better used for freshwater shells. There were no former long term temperature records for the lakes within the Tibetan plateau. The difference in the modern shell clump values and the fossil clump values can be explained by a change in global climate. The temperature difference between fossil shells and modern shells, after adjusting for temperature change due to sampling elevation difference, is similar to the change in the global mean temperature since the Pliocene warm period. This result tells us that the elevation during the Cenozoic was similar to today. These findings have important implications for paleoclimate and paleo-elevation reconstructions using clumped isotope data from aragonite fossil shells.

Why is this study important? This study provides additional paleo-temperature data that can be used for future paleoclimate research. The affect that tectonic events have on our climate can be significant and the significance of the Himalayan Orogeny on the climate is still disputed. This study can provide more insight on the temperatures of the surrounding areas during that time. Understanding the paleoclimate of our planet can help us better understand how it will react to things in the future.

Chart with water oxygen 18 values on the y-axis and study sites on the x-axis.
This figure represents the calculated d18O values using the Henkes calibration vs the Eagles calibration vs the actual d18O values of the water from the lake sites. The error bars indicate 1 standard deviation.

Citation: Wang, Y., Passey, B., Roy, R., Deng, T., Jiang, S., Hannold, C., … & Tripati, A. (2021). Clumped isotope thermometry of modern and fossil snail shells from the Himalayan-Tibetan Plateau: Implications for paleoclimate and paleoelevation reconstructions. GSA Bulletin133(7-8), 1370-1380.

Anoxic Conditions in the Northern Gulf of Mexico Predicted to Increase as Climate Change Continues

Climate change projected to exacerbate impacts of coastal eutrophication in the northern Gulf of Mexico

Arnaud Laurent, Katja Fennel, Dong S. Ko, John Lehrter

Summarized by Kristina Welsh, who is currently a junior at Binghamton University pursuing a B.S. in Environmental Science with a concentration in Natural Resources and a minor in GIS. Kristina hopes to pursue a job involving field work and travel opportunities. In her free time, Kristina enjoys camping, biking, and hanging out with her dog, Bailey.

What data were used: This study uses data from past published articles to compare present and future conditions intheGulf of Mexico. A present condition model was created using data from the Intra-Americas SeaNowcast-Forecast System. The future model was constructed using data from MPI-ESMRPC 8.5.

Methods: This study uses two 6-year physical-biogeochemical model simulations from the Regional Ocean Modeling System to represent present and future conditions in the northern Gulf of Mexico. Initial and open boundary conditions, river discharge, atmospheric temperature and pCO2 (atmospheric carbon dioxide) were variable in both models; all other factors were kept constant. The present simulation, which covers the period of 2005-2010, uses data from the Intra-Americas Sea Nowcast-Forecast System. The future simulation represents a 6-year period at the end of the century. The future model parameters were set with a 10% increased discharge from the Mississippi River, an air temperature increase of 3 ºC, and an atmospheric pCO2 increase to 935.85 µatm. Although conditions of river nutrient load were kept the same, the increased river discharge in the future model will dilute nutrient concentration results.

Four models (present on left, future on right) that show modeling results.
This figure illustrates the pH decrease in bottom waters that is predicted to occur in the future simulation. The bottom row shows how oxygen concentrations are expected to decrease.

Results: The future models predict a summer surface and bottom water temperature increase by 2.69ºCand 2.23ºC, respectively. The salinity of surface waters decreases by 0.48 due to an increase in freshwater river discharge in the model. As salinity in bottom waters is controlled by the saltier offshore water, only a decrease of 0.02 was observed. The reduced density of the warmer and fresher water lead to an increased stratification in summers by +12.35 J m^-3. These warmer waters cause lower oxygen saturation levels and thus lower oxygen concentrations, with summer surface oxygen concentrations 3.4% lower than the present average. The decrease in surface water oxygen saturation leads to a 9.4% decrease in oxygen concentrations in bottom waters. 60-74% of the decrease in oxygen concentration is a result of saturation-dependent effects, while the other 26-40% is a result of changes in biological rates and stratification. Lower oxygen concentrations in the Gulf of Mexico leads to an increase in extent and duration of future hypoxia conditions. Hypoxic areas increase by 26% and volume increases by 39%, resulting in more frequent anoxic surface and bottom waters. The future model increased surface pCO2 and alkalinity, causing a decrease in bottom water pH range of 0.37-7.58, with large spatial and temporal variability. Hypoxic waters in the Gulf predict an average pH 7.39. Present and future conditions vary year to year due to different along shore wind directions, upwelling, and river discharge, but overall follow the same trend.

Why is this study important? This study implies how human-induced climate change will exacerbate hypoxic conditions and eutrophication-driven acidification in the northern Gulf of Mexico by the end of the century. Future hypoxic conditions will create growth and reproductive impairment to many sensitive species living in the Gulf. Changes in atmospheric CO2 can influence ocean pH and air temperatures, producing other negative effects on water chemistry, and plant, and animal life, creating a positive feedback system that will exacerbate these changes. 

The big picture: This study adds to our understanding of the risks of climate change. As this model interprets the impacts of climate change on nature and human sustainability, we can visibly see how the Earth’s oceans will change globally as well as locally. This article gives us evidence as to why we need to take action now so these changes do not occur.

Citation: Laurent, A., Fennel, K., Ko, D. S., & Lehrter, J. (2018). Climate change projected to exacerbate impacts of coastal eutrophication in the northern Gulf of Mexico. Journal of Geophysical Research: Oceans, 123(5), 3408–3426. https://doi.org/10.1002/2017jc013583

Colonization and Sea Level Rise Effects on Carbon Storage in Freshwater Wetlands of Southeastern United States

The Impact of Late Holocene Land Use Change, Climate Variability, and Sea
Level Rise on Carbon Storage in Tidal Freshwater Wetlands on the Southeastern United States Coastal Plain

Miriam C. Jones, Christopher E. Bernhardt, Ken W. Krauss, Gregory B. Noe

Summarized by James Myers who is a graduate student at Binghamton University earning his masters in teaching for earth science. As an undergraduate he majored in environmental
chemistry. Not long after he decided he wanted to become an educator and work towards
creating the next generation of environmental scientists. In his downtime he enjoys playing
guitar, camping, and watching hockey.

What data were used: Sediment cores were collected along the Waccamaw River in South Carolina and the Savannah River in Georgia. The sites were chosen because they have similar landscapes, ranging from freshwater, to moderate salinity, and oligohaline marsh. Four piston core samples were taken from the Waccamaw River, one that was found in freshwater, one in moderately salt-impacted water, and two from the Sampit River, one from a heavily salt-impacted area and one from an oligohaline marsh. Four other cores were collected along the Savannah River using a peat corer. These core sites were also from freshwater, moderately salinated, highly salinated, and an oligohaline marsh.

Three maps of the Savannah river, Waccamaw River, and an inset map showing the location of both rivers along the southeastern United States.
Maps designating the locations of the sites sampled. The sites are roughly 150 km away from each other, along the southeastern coastline of the United States. The Savannah River sites are found further upstream compared to the Waccamaw River sites. The cores at both locations were assigned numbers from one to four. The lower numbers are further upstream and are lower in salinity.

Methods: The cores were dated using radiocarbon analysis on macrofossils and bulk sediment which helped determine which samples were from the colonial era. Time scales were reported with calibrated years before present from 1950. Core compression was apparent within the samples, and bulk density (weight of sediment in a given volume) and accretion rates (how fast sediment accumulates) were adjusted to account for this. Carbon content was calculated using the loss on ignition method. Carbon accumulation rates were calculated by multiplying the percent carbon by the bulk density and accretion rate determined from an age-depth model. Pollen analyses were run to understand which plant species lived at these sites over time, as this method revealed what the environment must have been like if certain plants and trees were able to survive.

Results: The core samples from the Waccamaw river dated between the last 1,100-4,200 years. The oldest sample was the heavily salt-impacted site, which began as a back swamp environment, where fine silts and clays settle after flooding which create a marsh-like landscape. This was determined from the presence of Nyssa, Taxodium, and Poaceae pollen. The accumulation rates are low, but still higher than the freshwater sites. Upper freshwater and oligohaline sites were also found to have been back swamps due to the presence of Alnus in the freshwater core, and Liriodendron tulipifera seeds found at the oligohaline marsh site, as well as Nyssa, Taxodium and Alnus pollen found at both sites. The accretion and accumulation rates are similar to the heavily salt-impacted site. Freshwater environments are characterized by low accretion and carbon accumulation. Higher accretion and carbon accumulation rates are found around 1700-1400 calibrated years before present, and can be seen in the cores with a decrease in hardwoods and increasing Nyssa, Taxodium, and Liriodendron evidence. The largest observed changes happened around 400 years ago, the same time of colonization and the increase in agriculture within the regions. The changes are marked in the cores by large increases in accretion, organic matter, and carbon accumulation. Another indicator of this is the increase of Poaceae, while evidence of Nyssa, hardwoods, and Taxodium diminish. Poaceae pollen and the presence of Scirpus and Carex seeds suggests a change to oligohaline marsh in relation to the increase of land use in the area. Reforestation efforts over the last 100 years show a decrease in accretion and carbon accumulation in all sites. The Savannah River cores were found to be roughly five to six thousand years old. The results from the cores along the Savannah River were found to be very similar to those from the Waccamaw River.
The study revealed that the same zones were also back swamps and that the freshwater core showed low accretion and carbon accumulation. The presence of Alnus designated this back swamp environment. Around 2,000 calibrated years before present, the sites show various changes in biota, but very little change in accretion and carbon accumulation rates. The largest change in the Savannah samples are found around 400 years ago, as was seen in the Waccamaw cores. All sites showed a decline in Nyssa, and an
increase in Poaceae, and what the researchers call weedier taxa, such as Scirpus, Sagittaria, and Polyganum. Both the Savannah River and the Waccamaw River both show stark increases in carbon accumulation and accretion rates right at the start of when colonization and agriculture increased in these regions dramatically, as well as when sea-level rise began to increase during the Holocene. The lowest accretion rates were found further inland, which is tied to an expansion of the marsh. Reforestation efforts coincided with lowered accretion rates, which increased the vulnerability with a rise in sea level. The tidal freshwater forested wetlands are vulnerable to the smallest of salinity changes.
Why this study is important? Wetlands like the ones studied in this research, are important for coastal communities because they help mitigate flooding and support many organisms, as well as fisheries, which provide millions of dollars in commercial and environmental goods and services. Wetlands are also important carbon sinks and help control the amount of CO2 in the atmosphere. Sea level rise today will affect these ecosystems and the people living near them. The results of this research are important for understanding the future long-term resilience of these ecosystems and what measures will be best suited to support these environments.
The big picture: The paper looked at evidence within sediment cores to understand the changes in carbon accumulation and accretion within two southeastern United States rivers. Core evidence indicated that there were increases in accretion and carbon accumulation rates with the emergence of colonization and agriculture in the area. Reforestation efforts in the last 100 years showed a decrease in accretion. The findings were then compared to sea level rise data to show that these environments become more vulnerable with increased sea level rises over the last 200-100 years. This research will be helpful in understanding the effects sea level rise in the future will have on this environment and the surrounding communities.
Citation: Jones, M. C., Bernhardt, C. E., Krauss, K. W., & Noe, G. B. (2017). The impact of late Holocene land use change, climate variability, and sea level rise on carbon storage in tidal freshwater wetlands on the southeastern United States coastal plain. Journal of Geophysical Research: Biogeosciences, 122(12), 3126–3141. https://doi.org/10.1002/2017jg004015

How global warming is changing the ecosystem in the Alps and Apennine Mountains

Assessment of climate change effects on mountain ecosystems through a cross-site analysis in the Alps and Apennines

Rogora M., Frate L., Carranza M.L., Freppaz M., Stanisci A., Bertani I., Bottarin R., Brambilla A., Canullo R., Carbognani M., Cerrato C., Chelli S., Cremonese E., Cutini M., DiMusciano M., Erschbamer B., Gogone D., Iocchi M., Isabellon M., Magnani A., Mazzola L., Morra di Cella U., Pauli H., Petey M., Petriccione B., Porro F., Psenner R., Rossetti G., Scotti A., Sommaruga R., Tappeiner U., Theurillat J.-P., Tomaselli M., Viglietti D., Viterbi R., Vittoz P., Winkler M., and Matteucci G.

Summarized by Agnes Wasielewski, who is an MAT Earth Science Graduate student at Binghamton University. She loves Geology so much that she decided to share her passion with middle and high school students by becoming a teacher. When she’s not studying Geology or the psychology of teenagers; she spends a lot of time with her husband, three children, and three dogs. When free time becomes available, she loves to read, hike, drink tea, and take naps with her dogs.

What data were used? Researchers collected data from twenty research sites across the Alps (Italy, Switzerland, and Austria) and Apennines Mountains (Italy). All sites were located between 1300 and 3212 meters above sea level. Fourteen sites are in forests, grasslands, alpine tundra, and snow-covered areas. Six sites are in lakes and rivers. All sites considered for the paper experienced an increase in air temperature over the past two decades (1991-2015) compared to a base period of 1961-1990. A combination of data analysis on already existing datasets, projects, and new collection of data to determine results.

Methods: Temperatures taken in June were used to determine snow melting rates, the timing of the beginning of the growing season, and timing of ice-break in lakes and rivers. To analyze regional snow cover duration, data loggers combined with thermistors (special resistors used  for temperature measurements) were placed at a soil depth of 10 cm and measured hourly. If the temperatures measured remained within a certain range, the day was considered a “snow cover day”. On days where the daily mean soil temperature dropped below and rose above 0 degrees Celsius, they were labeled as a freeze/thaw cycle. The snow melting date is identified by counting the days since October 1st to the start of the freeze/thaw cycle or melting period. Soil samples were collected in September at the end of the growing season and tests are run to determine water content, carbon content, and nitrate concentrations. 

Changes in vegetation cover were calculated by estimating the percentage of each plant species in permanent grids over time. These estimates are used as a proxy for above-ground biomass. Biomass is positive when vegetation cover increases and negative when cover decreases. 

Surface water samples for chemical analysis were obtained from lakes in late summer/early autumn. May to October is considered open water season, and water temperatures combined with chlorophyll-a concentrations and zooplankton abundance are recorded. Weather stations were used to collect average air temperatures. Biologic samples were analyzed from rivers at varying distances downriver of melting glaciers to correlate community composition and diversity.

Location of research sites where data was collected throughout the Alps and Apennine mountains in central and northern Italy, southern Switzerland, eastern and central Austria.
Location of research sites used for analysis within Italy, Switzerland, and Austria. Degree of temperature change from the baseline reflecting global warming.

Results: At lower altitudes (~1500 meters above sea level) and latitudes (Lat. 41 degrees N), there are shorter snow cover duration (less than 100 days/year) and snow starts to melt earlier in the year. At higher altitudes (~2800 meters above sea level) and latitudes (Lat. 46 degrees N), there are longer snow cover duration periods (~250 days) and snow starts to melt later in the year. Less snow-covered days allow for increased soil temperatures and more areas for plants to grow and thrive. When more plants can grow and thrive, there are more resources available to local wildlife such as the Alpine ibex (mountain goat) and helps support their population growth. Overall, increased air temperatures and soil temperatures showed a general tendency towards increased vegetation cover for treeline, subalpine, and alpine belts but not in the snow (nival) belts. Over the last fifteen years, it is noted that plant species have been migrating from lower elevations to higher elevations in a process called thermophilization.

An increase in nitrogen deposition has positive effects on tree growth and promotes carbon sequestration (the process of capturing and storing atmospheric carbon dioxide). However, reduction in rainfall can override the positive effects. In the forests tested, a significant increase in the growing season length and a general increase in the annual net carbon sequestration was detected.

During warm and dry years, alpine streams transport concentrated solutes into the lakes and in the runoff water. Over the past decade, there has been a common trend in decreasing nitrate concentrations. Nitrogen uptake in the lake catchments has increased due to the increase in primary productivity (algae and vegetation growth). There has an overall negative trend in NO3 concentration level in rivers and lakes due to decreasing Nitrogen deposition. 

Changes in water mineral and chemical concentrations also affect the diversity and population of algae and plankton that live and thrive in mountain lakes and streams.

Why is this study important? Climate warming effects, changes in rainfall seasonality, and water availability have proven to be important for ecosystem productivity. Snow cover duration affects soil carbon and nitrogen cycling and Alpine ibex population dynamics. Warming climate change has shown to lead to an increase in vegetation cover in grasslands and carbon uptake in forests which helps remove CO2 from the atmosphere. Climate drives changes in water chemistry, lake thermal dynamics and plankton phenology can inform us of the health of the water ecosystems. High-elevation ecosystems may also be affected by extreme climatic events such as heat waves, droughts, heavy rainfall, and floods. Both long-term and short-term (extreme) events can affect mountain ecosystems. Mountain ecosystems, if properly studied and monitored, can serve as early indicators of global changes.

The big picture: Global warming affects high mountain ecosystems by increases in temperature, early snowmelt, and a prolonged growing season. With ecosystem productivity, more plant growth helps reduce global climate change by reducing the amount of carbon dioxide in the atmosphere. In mountain ecosystems, carbon sequestration depends on both water availability (precipitation) and air temperature. The understanding of hydro-ecological relationships is essential for the development of effective conservation strategies for alpine rivers. Long-term observations on benthic communities help with the assessment of the potential impacts of global change on stream ecosystems. There is a great need for strong partnerships in mountain ecosystem observation and research for multidisciplinary approaches, encompassing the distinction between different types of ecosystems. There is great potential for further scientific advances that rely on international collaboration and integration.

Citation: Rogora, M., Frate, L., Carranza, M. L., Freppaz, M., Stanisci, A., Bertani, I., Bottarin, R., Brambilla, A., Canullo, R., Carbognani, M., Cerrato, C., Chelli, S., Cremonese, E., Cutini, M., Di Musciano, M., Erschbamer, B., Godone, D., Iocchi, M., Isabellon, M., … Matteucci, G. (2018). Assessment of climate change effects on mountain ecosystems through a cross-site analysis in the Alps and Apennines. The Science of the Total Environment624, 1429–1442. https://doi.org/10.1016/j.scitotenv.2017.12.155

Echinoderm Morphological Disparity

Echinoderm Morphological Disparity: Methods, Patterns, and Possibilities

Bradley Deline

Summarized by Whitney Lapic,  a Time Scavengers collaborator and graduate student in paleontology. Whitney studies the paleoecology of extinct echinoderms including blastozoans. Outside of research and class time, Whitney is with her cat, Quartz, and can be found tending to her numerous houseplants. 

This paper serves as a review of different approaches for and the importance of studying morphological disparity, or varying expressions of physical characteristics across a group of organisms. Since the 1960s, the importance of examining morphological disparity among organisms has become increasingly apparent. Early studies observed disparity at varying taxonomic ranks (e.g., the diversity in a phylum, like Mollusca, the group including snails and clams) while others applied numerical approaches to quantify morphological disparity. Regardless of a quantitative or a taxon–based approach, there is a need for developing some metric to quantify disparity.  

What data were used?: While this article does not collect new data, it synthesizes a collection of studies done on echinoderm disparity. Echinoderms, the group including sea stars and sea urchins, offer an opportunity as a model organism for studying morphological disparity. Echinoderms are highly skeletonized and can be abundant and well preserved in the fossil record. Additionally, they present a wide variety of morphologies and are both ecologically and taxonomically diverse. While studying disparity among echinoderm morphologies has significantly helped address some gaps in our knowledge, studying disparity still offers opportunities to explore echinoderm evolution. 

Methods: This study reports multiple methodologies and discusses them in depth with their applications, benefits, and caveats. These methodologies include morphometric approaches using landmark-based geometric morphometrics, as well as discrete character-based approaches. Landmark based morphometrics involves the identification of easily recognizable features, such as the point of contact between two plates that can be measured across individual organisms. Landmark based approaches can assist in differentiating species, studying the growth of a species throughout its ontogeny (growth and development), and can help in studying the disparity of a group through time. 

Alternatively, character-based methods are often used when fossils are too damaged to do landmark analysis. When continuous measurements of characters cannot be obtained, the expression of a character is divided into categories into which individuals may be placed. This approach presents as a coded matrix in which expressions of a morphological feature would be coded as, for example, 0, 1, 2, etc. as a means of using discrete categories. Realistically, a combination of the two are used in these types of studies. We want to utilize as many approaches as possible. When we obtain comparable results using multiple methods, this is vital in our understanding of and interpretation of potential evolutionary trends. 

The variable morphologies and the differences among them can help us explore the morphospace of echinoderms. Morphospace is a graphical representation of all forms of physical characteristics that a particular group can present with. Understanding the morphospace of taxa, and specific regions of a taxon’s morphospace can provide insight into its resiliency and susceptibility to extinction and diversification. For example, we can consider the variable morphologies of echinoderms and how very different morphologies can assist in their survival in different environments. 

A figure with a black background and white text has high resolution, black and white photos of six echinoderms labelled A through F with their respective scale bars. In the first of two rows, starting on the left: specimen A) an oblong, non-radial form of echinoderm next to a scale bar of 1mm. The outer plates of the echinoderm are large, and rectangular while the inside is comprised of smaller plates. To the right, B) a misshapen, circular edrioasteroid with apparent 2-1-2 symmetry seen in the ambulacra. Plates of many sizes can be seen around the ambulacra which form almost a star shape. The scale bar for this specimen is on the bottom left and reads 5 mm. Specimen C) shows a circular, mobile echinoid. The echinoid is crushed, but may show some short spines. Scale bar is located on the bottom left and reads 5 mm. On the second row, from left to right: D) a branching, stalked, crinoid with the calyx, or central part of the body, oriented downward. Scale bar is 5mm. E) a relatively circular diploporitan echinoderm. Five slightly curved ambulacra can be visible. Scale bar is 5 mm. On the bottom right, specimen F) a stalked eocrinoid. The stem is oriented downward with the theca, or body, showing a complex series of circular structures. From the theca, there are five arms extending from the top of the theca and outward. The scale bar is 5 mm and is at the bottom left of the image.
Figure 1: Six echinoderms from the early Paleozoic. The six specimens show a range of body plans that can be found among Cambrian and Ordovician echinoderms. Figure from Deline et al., 2020. A) Ctenocystis showing the non-radial form of a ctenocystoid. B) Edrioaster, an attached pentaradial edrioasteroid. C) The mobile echinoid, Bramidechinus. D) Anomalocrinus, a pentradial stalked crinoid. E) Gomphocystites, a pentaradial stalked diploporitan. F) Sineocrinus, a pentaradial stalked eocrinoid. Image from Deline et al. (2020).

Why is this study important?: This paper addresses the ways in which echinoderm morphologies and their disparity can be used to further investigate echinoderm evolution. There has been a rich history of utilizing disparity and morphological approaches to study echinoderm evolution, however, there are several opportunities for further study. This paper highlights the need for combining both phylogenetic study and morphologies to gain further insight into evolutionary processes, both those including, and beyond, echinoderms.

The big picture: Understanding disparity is critical to our interpretations of trends in evolution, as well as to the development of methods to test hypotheses regarding the relationship between disparity and extinction events. By quantifying variation in morphologies, we are able to both provide a metric for understanding the degree of change in morphology during the evolution of a lineage and to explore selection towards particular morphologies surrounding extinction events.

References: 

Deline, B. (2021). Echinoderm Morphological Disparity: Methods, Patterns, and Possibilities. Elements of Paleontology, Cambridge.

Deline, B., Thompson, J. R., Smith, N. S., Zamora, S., Rahman, I. A., Sheffield, S. L., Ausich, W. I., Kammer, T. W., Sumrall, C. D. (2020). Evolution and Development at the Origin of a Phylum. Current Biology, 30, 1672-1679.

Combining our past life with our present improves the foundation and deeper understanding of our evolutionary tree

Fossils improve phylogenetic analyses of morphological characters

Nicolás Mongiardino, Russel J Garwood, Luke A. Perry.                                                         

Summarized by Sadira Jenarine, a senior at The University of South Florida. She is a geology major and plans on attending graduate school following graduation in the summer. Once she earns her degree, she hopes to work along the lines of environmental conservation and preservation or become a professor. When she’s not looking at rocks, you can usually find her at the local Starbucks making a latte or in the town’s own “Lettuce Lake Conservation Park”.     

What data were used: The authors conducted a simulation of 250 evolutionary trees, also called phylogenies, which were used to determine the most accurate method of creating phylogenetic trees. Programs were designed to account for species’ traits, including strengths and weaknesses as well as their ability and likeliness to survive natural disaster, such as mass extinction events, and/or predation.     

Methods: This study was completed by testing different phylogenetic inference methods: maximum parsimony (MP), Bayesian inference (BI) and tip-dating. MP is essentially the path of least resistance in evolution; the fewer branches you must jump on “the tree of life”, the more closely related a species likely is. Bayesian inference, combined with tip-dating is a method of dating fossils by analysis that gives a numerical age of the specimen, and then tests whether it is statistically accurate using an equation called Bayes Theorem. These methods differ from a more common technique, ‘node dating’ which determines the age through age constraints that are formed by the first and last seen specimen in the fossil record. These new forms of analysis were tested based on the 250 trees as well as over 11,000 different traits that these organisms share. 

Results: This experiment was conducted by testing the results of the length of the simulated evolutionary trees. The graph (Figure 1) measures the accuracy of the placement of the species on the tree among all inference methods performed by testing different accuracy measures, which are measured by using the number of nodes (i.e., the branching point on an evolutionary tree). We see that even with accounting for missing data (i.e., when species don’t have the entire suite of characters used in a phylogenetic analysis), one type of accuracy, quartet-based accuracy, increases proportional to the fossil sample. In turn, bipartition-based accuracy shows a difference in accuracy when there is missing data. This effect is mostly seen when examining tip-dated inference which uses multiple morphological (body shape) and molecular (DNA) data from fossils themselves. Tip-dating is a newer method of inference and should therefore be used with caution, as it is sensitive to missing data, something very common when using fossils. 

Graph in top left measures the topological accuracy of bipartitions based on the proportion of missing fossils in maximum parsimony (MP), Bayesian inference (BI) and tip-dating (clock). No missing data concludes a higher accuracy in all 3 inferences with the most outstanding in clock dating. Even amongst high levels of missing data, the topological accuracy for clock dating is outstanding in comparison to other methods. The bottom left graph measures the same variables however with quartet-based analysis. This graph remains the same even with different levels of missing data. The graphs to the right measures the topological precision. In MP precision decreases as more levels of missing data are introduced, same with BI and clock, however not as outstanding. In quartet-based analysis all three inference methods maintain similar precision even amongst missing data.
Figure 1. The graph shows both topological accuracy (left) and topological precision (right) using both forms of measurement; bipartitions (top) and quartet (bottom). Colors indicated in the graph account for the levels of missing data. Amongst all methods, we see increased accuracy than that of parsimony. Issues arise with the tip-dating (clock) method when levels of missing data are high.

Why is this study important? Using complete morphological and/or molecular data of fossils, as well as data from living organisms, provides the most accurate evolutionary tree reconstruction. This shows us that tip-dating, which is the inclusion of fossils into the construction of the evolutionary tree, creates a more accurate and precise tree. This study compares its results to those from previous analyses and examines a new angle: accounting for missing data. This is beneficial, because this study helps us understand the limitations of a number of methods, which can help us create more realistic phylogenies. 

The big picture: Here, we are learning that using fossils along with modern species, when many studies use just modern species or just fossil species, really gives us a more accurate representation of how life on Earth has evolved through time. Because some of these methods of inference are newer, like tip-dating, there is much room for progress and development. By no means does it mean that new methods should be immediately widely accepted, but that it is our duty to continue to study this new form of inference dating. By understanding how what we have, what we had, and what we lost, we can get a better grasp of the evolutionary tree that we are working to perfect.   

Citation: Mongiardino Koch, Nicolás, et al. “Fossils Improve Phylogenetic Analyses of Morphological Characters.” Proceedings of the Royal Society B: Biological Sciences, vol. 288, no. 1950, 2021, https://doi.org/10.1098/rspb.2021.0044. 

Paleocene-Eocene thermal maximum (PETM): a potential foresight into the future of ocean life

Shallow marine ecosystem collapse and recovery during the Paleocene-Eocene Thermal Maximum

Skye Yunshu Tian, Moriaki Yasuhara, Huai-Hsuan M. Huang, Fabien L. Condamine, Marci Robinson

Summarized by Mathew Burgos, University of South Florida undergraduate geology student. Interested fields of study include solar radiation, hydrology, hydrogeology, hydroelectricity, geochemistry, and environmental sustainability.

What data were used? Rich fossil records of ostracod arthropods (the group that also includes spiders, trilobites, and insects), extracted from a Salisbury embayment (i.e., a recessed coastal body where there is a direct connection to a larger body of water) near the coast of Maryland, eastern United States. Ostracods inhabit nearly all aquatic environments on earth; their tiny shells make them look like “seed shrimp”, and they were among the only marine invertebrate fossils with a strong enough fossil record to reconstruct the group’s response to the PETM (Paleocene-Eocene thermal maximum), a time on Earth where the global temperatures skyrocketed for a geologically short period of time. A core sample was utilized to study the ostracods; a core is a cylindrical section of the Earth where the sediments, rocks, and organisms within are removed from the subsurface for analyzation. 

Methods: A sediment core was dug from the ground in the embayment, and the ostracod content within the core was analyzed for carbon-13 isotope values, to later determine the survival rate of the species during and post-PETM. Studying fossil records of creatures that existed during that time may lead to future impacts on marine life and our oceans future health. Carbon-13 isotopes can indicate periods or events of warmer temperatures when the values trend negatively, so the isotope values here helped identify the stages of the PETM alongside the fossils. The PETM (Paleocene-Eocene Thermal Maximum) is an event that occurred roughly 56 million years ago, and it was a climatic event similar to the current global warming crisis because of prolonged greenhouse climate conditions; however, the current crisis is happening at a much faster rate.

Four panel image with differences described in caption. Each panel represents a time slice to show the changes in environment that is tracked by marine species.
Top left, Pre-PETM setting: regular oceanic conditions for marine life above the oxygen minimum zone (OMZ).
Top right, During peak PETM: shallow marine migrating upslope for survival. Deep low oxygen species also moving upslope and separating from their fellow deep marine species that are adapted to low oxygen.
Bottom left, Recovery phase I: Species that survived the PETM returning to pre-event locale above OMZ.
Bottom Right, Recovery phase II: Mixing of potentially new warm adapted species and shallow marine species.

Results: Analysis of the ostracod abundance illustrated a substantial elimination of the shrimp just before the thermal maximum event, followed by a recovery and diversification of the species once the ocean temperature normalized a couple of million years later. Potential detriments of the thermal maximum are the irreversible impact that climate change had on the marine life, primarily due increased temperature and deoxygenation of the water. As deoxygenation spread (Figure 1), only species who were able to move into different areas of the water column were able to survive; those who could not went extinct. Some species nearly went extinct during the PETM but were able to recover and diversify after the event, even potentially returning to a healthy population. 

Why is this study important? This study made connections between the PETM and modern climate change that is human-driven, which is extremely harmful to marine life, as the PETM is likely the best analog to the current climate crisis. Effects of modern-day climate change are like the happenings of the Paleocene-Eocene Thermal Maximum. This is an indicator of the importance of the impact humans could possibly have on the ocean in a short period of time, relative to the Paleocene and Eocene Epochs.

The big picture: The recent global warming effects that humans have had on could prove to be detrimental to our existence. This study focuses on the PETM that occurred over a vastly longer time scale compared to the short duration of the current age of industrialization. Humans are essentially replicating an extreme thermal event, that would otherwise be relatively naturally occurring in Earth’s time, but at a rate which is exponentially smaller in timeframe. With the status of the Earth’s oceans warming, we could potentially see the ramifications of eliminated marine species within our time at an unprecedented rate.

Citation: S.Y. Tian, M. Yasuhara, H.-H.M. Huang, et al., Shallow marine ecosystem collapse and recovery during the Paleocene-Eocene Thermal Maximum, Global and Planetary Change (2018), https://doi.org/10.1016/j.gloplacha.2021.103649

An Important Look Back on the Unjust Past of Paleontology

Our past creates our present: a brief overview of racism and colonialism in Western paleontology

Summarized by Kaleb Smallwood, a junior undergraduate geology student at the University of South Florida who intends to use his degree to pursue a career in vertebrate paleontology. Outside of geology, his interests include video games, anime, and mythology.

Rather than a traditional scientific study using data and presenting results, here the authors attempt to unravel the racism, coverings, exclusion, and colonialism of paleontology’s past in order to better understand the racism present in the sciences today and how best to go about rooting this bias out. 

Since the inception of the discipline, paleontologists have extracted fossils, minerals, and fossil fuels from other lands, often without regard to the Indigenous peoples or otherwise residing there. This results in environmental destruction and displacement, as the scars left by this extraction tear up land and plants, leaving holes where digs occurred. On the topic of environmental devastation, the history of paleontology is also inextricably linked to the oil, coal, and gas industries. Paleontologists have served these industries in the location and extraction of nonrenewable resources in exchange for funding, job security, and support since they began to better understand how and where oil forms, implicating them in climate change. Another form of extraction exercised by paleontologists is that of biological specimens, both living and dead. For example, the several species of the finches (Figure 1) Darwin studied and extracted on his voyage on the HMS Beagle, such as the saffron-cowled blackbird and vampire finch, were pulled from their habitat and sent to Europe. Paleontologists have also participated in grave robbing, removing the remains of Native Americans and Black slaves to examine their cranial structures in an effort to further their racist views that these peoples are more closely related to primates than white people. Many of these remains of people are still held in storage and studied. While the loss of biodiversity from an ecosystem is a grave consequence of extraction of animals, the removal of humans from their lands is also an egregious crime of paleontologists. It is a flagrant act of disrespect to the culture and lives of the people from which they are taken. 

There is also the issue of the Myanmar amber trade, from which paleontologists have gained amber for examination in exchange for money that has been used to fund a decades-long civil war resulting in numerous deaths. Measures to limit and prohibit the publication and procurement of such amber have been put in place, but not all are ubiquitously accepted. Scientists are strictly forbidden, however, from publishing on Myanmar amber obtained after the most recent coup in February 2021.

Depicted are three type specimens of birds from Darwin’s voyage on the HMS Beagle. They appear as mockingbirds with light brown feathers on their underside and darker brown and white feathers on the wings. They are ordered by increasing size, with the smallest at the top of the image and the largest at the bottom. The eyes of the birds are missing, and they have tags tied around their feet displaying their taxonomic names. From top to bottom they are labeled as Orpheus parvulus, Orpheus melanotis, and Orpheus trifasciatus.
Figure 1. Specimens of birds from Darwin’s voyage on the HMS Beagle. From top to bottom they are labeled as Orpheus parvulus, Orpheus melanotis, and Orpheus trifasciatus. Image Credit: “Voyage of HMS Beagle (1831-1836).” Natural History Museum, Natural History Museum.

Returning to the topic of museums, scientists often take materials from other countries and peoples for the purpose of education and exhibition without asking, and this colonial way of obtaining their exhibits is cited as a cause for concern. Museums often refuse to acknowledge the methods by which they procure their items, do not credit the places they got them from, refuse to compensate these countries or return their property, have disproportionate wealth and resources compared to other museums, lack diversity in their staff, and pay their staff little for their work. Accountability, inclusion of the voices of the people whose history they display, and a willingness to return items would go a long way in correcting these flaws.

There are also injustices present in the teaching of paleontology. As the authors point out, textbooks and courses in the Americas tend to omit the ways in which scientists in the field have previously trampled upon Black and Native American people. For example, the erasure of their history and the fact that the first known fossils in the Americas were discovered by slaves is rarely mentioned. As is apparent, science has never been the unbiased and apolitical field students are led to believe it is. Furthermore, these courses are often taught by white men, further excluding other racial groups. The power system this creates makes it difficult for those with concerns to voice them for fear of reproach.

Why is this important/The big picture: Underscoring each point in this article is the constant reminder that the challenging task of acknowledging and reflecting on the past and current racially discriminatory of paleontology, the geosciences, and science as a whole, is a crucial first step in resolving those same issues. The writers call on paleontologists to consider whether the specimens they use come from Indigenous lands and ask who truly owns their specimens; they ask paleontologists to consider the people that their research may impact and their role in it, as giving proper credit to the right people without bias or exclusion is a crucial practice in any field, not just the sciences.

Monarrez, P., Zimmt, J., Clement, A., Gearty, W., Jacisin, J., Jenkins, K., . . . Thompson, C. (2021). Our past creates our present: A brief overview of racism and colonialism in Western paleontology. Paleobiology, 1-13. doi:10.1017/pab.2021.28 

Antarctic foraminifera and their implications on paleoclimate

Holocene foraminiferal assemblages from Firth of Tay, Antarctic Peninsula: Paleoclimate implications

By: Wojciech Majewski & John B. Anderson

Summarized by: Baron Hoffmeister

What data were used?: This study analyzed 166 sediment samples taken from sediment cores in the Antarctic Peninsula. 

Methods: This study used a quantitative analysis of foraminifera assemblages found in sediment cores to determine past environmental factors relating to climate change.  

Results: This study found that different foraminifera and their physical attributes correlate with several different environmental conditions during the Holocene epoch, the geologic time unit that spans from nearly 11,000 years ago to present time ( figure 1). A time span between 9400 years and 7750 years before present time was correlated with having coarse (large) sediment and coarse foraminifera. This indicates a high influence from warming sea currents that melted glaciers and deposited coarse sediments. This was a period of glacial retreat and warming temperatures. From 7750 to 6000 years before the present, the elevated appearance of foraminifera species M. arenacea represents open water and conditions in which glaciers were spread out from each other. The foraminifera species M. arenacea is also known for its tolerance to cold corrosive bottom waters and high salinity fluctuations. The assemblage dominated by M. arenacea indicates that the bottom waters at this time dissolved other species of foraminifera, and M. arenacea was the dominant foraminifera species at this time. Foraminifera tests, (i.e., their shells) are made of calcium carbonate, and it dissolves in acidic conditions. Around 3500 years before the present time, it was found that due to an increase in abundance of foraminifera species P. bartramiP. antarctica is when the cooling trend of the mid-Holocene occurred. There weren’t any corresponding foraminifera assemblages found that correlate with warming over the last century. 

Image contains many examples of foraminifera at different angles to showcase the variation and how it can be employed as a tool to assess climate.
Different species of foraminifera can be used to identify different ecological conditions in which they existed. The physical properties of foraminifera, like roundness or angularity of their tests, can also determine transport history, depositional environments, and likely effects from environmental influences. This is a microscopic image of several different foraminifera species found in the core samples used for this study. The different shapes of this foraminifera and the textures observed were used to determine environmental conditions in the Antarctic peninsula.

Why is this study important?: The results of this study allow us to better understand how foraminifera can relate to changing environmental conditions. This study provides a more cohesive understanding of climate change and how glacier and ocean currents around the south pole respond to changes in climate. The data used in this study can be used in future studies regarding foraminifera assemblages and their implication on climate change. 

The big picture: Foraminifera are some of the most abundant shelled organisms in marine environments and can be used to reconstruct past climatic conditions. The importance of understanding how these organisms correlate to climate change can help link current-day climate trends to prehistoric climate events. This can be used to make predictions on how climate change is occurring currently, and what the effects of it might be worldwide. 

Citation: Majewski, W., & Anderson, J. B. (2009). Holocene foraminiferal assemblages from Firth of Tay, Antarctic Peninsula: Paleoclimate implications. Marine Micropaleontology, 73(3-4), 135-147. doi:10.1016/j.marmicro.2009.08.003

Paleoclimate implications from a sediment core taken in a frozen Antarctic lake

Limnological Investigation of Antarctic Lakes and their Paleoclimate Implications

By: Pawan Govil

Summarized by: Baron Hoffmeister 

What data were used?: A 78 cm sediment core from a freshwater lake in Larsemann Hills, East Antarctica was used to interpret historic climate patterns from the late Quaternary period. 

Methods: The sediment core was analyzed using grain size distribution, as well as biological productivity indicators such as organic carbon and biogenic silica. Biogenic silica makes up diatom cell walls and is commonly called opal. This study used radiocarbon dating to measure total organic carbon present, and the biogenic silica was also evaluated using a wet alkaline extraction. A wet alkaline extraction is a method that isolates plasmid DNA or RNA from bacteria. This was used to determine the biogeochemical attributes of this lake.

Results: Using radiocarbon dating, this study found that this core is from the Holocene Epoch, a time that began around 11,700 years ago. This core was dated to be 8,300 years old. Most of the material in the core was sand, and clay and silt were rarer (sand, clay, and silt are defined by grain size in geology- sand is the coarsest grain size in this example; figure 1)The silica content within this was very low, indicating a very low abundance of silicate microfossils. The total carbon was low or negligible in the lower part of the core, likely due to the high sedimentation rates of sand during this time. The area of the core that had the most organic carbon was the top of the core that contained the small amounts of clay and silt. This study showed that this was due to a build of algae. The particles of clay and silt prevented oxygen from  decomposing the organic matter. This indicates that during this time, approximately 4,000 years ago, there were low sedimentation rates and low oxygen levels in this lake. This algal mat at the top of the core indicates warming temperatures during this time, and that the lake had little interference with glacial ice. The fine grained sediments were deposited due to ice meltwater (as water slows down, fine grained sediments drop out of water suspension) and can be seen in the upper core. The lower portion of the core contains high sand content, which implies glacial river input (i.e.,fluvioglacial) before 6,000 ago. The overall paleoproductivity implications of the core are as follows.  From 8,300 ago to around 6,000 years ago there was a period of warming. Around 4,000 ago, the warm temperatures allowed the lake to be free of ice and exposed to sunlight, and therefore this was the highest level of productivity and can be reflected in the upper core’s higher total carbon content. 

Graph depicting age dating of a sediment core.
This is a chronological interpretation of the sediment core taken from this study. Sand dominated the core with low percentages of silt and clay. This graph shows records dating back to 8.22 thousand years ago (right) working its way to around 1 thousand years ago (left).

Why is this study important?: Antarctica and its surrounding oceans influence climate across the entire planet. Antarctica holds around 90% of the world’s ice and about 70% of the world’s freshwater trapped in ice. The ability to be able to interpret past climate conditions that influenced climate patterns in Antarctica can allow scientists to better predict current day climatic changes in Antarctica and its effects globally.  More information about Antarctica and its ice sheets can be found here

The big picture: Today, the ice sheets are melting at a rate that has never been seen before. The effects of this could be catastrophic to life on Earth. Studies like these can allow scientists to better understand current-day climate patterns that could potentially help reduce the impact of widespread climate change. 

Citation: Govil, P. (2019). Limnological Investigation of Antarctic Lakes and their Paleoclimatic Implications. Ministry of Earth Sciences, (24), 289-303. Retrieved May 24, 2020.