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Antarctic foraminifera and their implications on paleoclimate

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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. bartrami–P. 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

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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.

New Late Cretaceous Shark found in North America

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A new large Late Cretaceous lamniform shark from North America, with comments on the taxonomy, paleoecology, and evolution of the genus Cretodus

by: Kenshu Shimada, Micheal J. Everhart

Summarized by: Baron Hoffmeister

What data were used? : This study examined a partial skeleton of the Late Cretaceous shark, Cretodus, collected from the Blue Hill Shale in north-central Kansas, U.S.A. It had unique teeth not present in any other species of Cretodus. 

Methods: This study used a taxonomic analysis of the fossilized remains found and compared them to other members of the Cretodus genus. 

Results: The study found that the species of the fossilized partial shark skeleton found does not share enough similar features with any of the other four known species within the genus Cretodus. Therefore it has been listed as a new species, C. houghtonorum. Researchers found that it had a unique tooth size and pattern that didn’t match any previously discovered species (figure 1). Its calcified cartilage scales along with the inference that this shark had a large girth due to its bone structure that was preserved, indicated that this organism was likely a sluggish shark that lived in a nearshore environment. This study examined growth bands in its vertebral column and found that this shark had a lifespan of around 51 years. 

Image of many shark teeth from various angles to showcase how many different types of teeth exist for sharks
These are the 115 well-preserved teeth of C. houghtonorum. Sharks shed their teeth over their lifespan, and have several rows of teeth in both their upper and lower jaws. As one tooth falls out, it is replaced by the one in the row behind it. Each species of shark has unique teeth and jaw structures.

Why is this study important? Aside from discovering a new species, this study recognizes the fact that the evolutionary relationships of several shark families is still relatively unknown. However, this new finding provides data linking it with other members at the genus level. Without understanding these relationships, it’s difficult to understand the distribution of these organisms, how they changed over time, and why they went extinct. 

The big picture: Overall, this study is useful in determining possible links between extant and extinct shark species. This study provides data that can rework our understanding of evolutionary traits between extinct and modern-day sharks as well. The skeletal and dental data found in this study can be useful for other studies incorporating evolutionary trends, prehistoric ecology, and the taxonomic differences within the genus Cretodus.

Citation:  Shimada, K., & Everhart, M. J. (2019). A new large Late Cretaceous lamniform shark from North America, with comments on the taxonomy, paleoecology, and evolution of the genus Cretodus. Journal of Vertebrate Paleontology, 39(4). doi: 10.1080/02724634.2019.1673399

Sauropods of the Mahajanga Formation, and Changing Lifestyles of the Middle Jurassic

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Sauropod Teeth from the Middle Jurassic of Madagascar, and the Oldest Record of Titanosauriformes

Gabriele Bindellini and Cristiano Dal Sasso

Summarized by Reynolds Hansen. Reynolds Hansen is an undergraduate geography major / geology minor at the University of South Florida. With a lifelong passion for paleontology instilled from an early age, Reynolds always knew the academic path ahead had a singular destination. Along the way, he picked up equal affinities for history and geography, and by the time he was in college, he worried he might have to choose one over the others. With the help of the university’s esteemed academic professionals and resources, he shifted focus with the goal of becoming a science communicator, telling the story of our world from the formation of the earth to the modern day as an interconnected narrative. Reynolds is set to graduate in the spring of 2021, after which he wishes to seek a post-graduate degree in paleontology, and a career as an educator. His academic focus is utilizing GIS to research paleoecological phenomena.

Data used:  The 31 fossil sauropod (the group including long neck dinosaurs) teeth described in this work are all from the Mahajanga Formation of Madagascar. The teeth are often the only recoverable remains for these animals, as intense weathering typically reduces most other bones to a powder-like state.

Methods: Researchers took qualitative and quantitative measurements of the teeth to reconstruct the amount of physical wear and abrasion to record observations of physical wear or abrasion, and determine possible diet according to tooth features, positioning in relation to neighboring teeth, and evolutionary derivation. Measurements were obtained via the use of digital calipers on targeted areas of interest on the teeth, specifically, from four regions around the crown of the tooth. The results of these measurements grouped teeth into one of four categories: heart-shaped teeth, spatulate teeth, compressed cone-chisel teeth, and pencil-shaped teeth (or peg-like teeth; fig.1). Finally, these measurements were compared against known sauropod species tooth dimensions to come to conclusions on species taxonomy and ecology (fig. 2). 

Figure 1: The four tooth types outlined in the findings of the paper and labeled respectively. Notice the progression from left to right, where enamel wrinkling decreases and tooth becomes more peg-like. This spectrum is also representative of the progression in sauropod tooth morphology seen over time.

Results: With the methods described above, the researchers were able to categorize the 31 teeth into eight morphotypes, or broad shapes. They were then able to categorize these morphotypes further into four possible taxa (species), based on a number of factors including comparative analysis of tooth features, knowledge of local species (or lack thereof), and a combination of these two points against the total current knowledge of sauropod tooth shape. Most of the morphotypes are tentatively assigned to two possible species: Bothriospondylus madagascariensis, or Lapparentosaurus madagascariensis (taxa A and B). Scientists don’t yet understand the relationships of taxon A to other sauropods yet, but taxon B may be related to groups like brachiosaurs or titanosaurs. Two morphotypes (taxon C) are tentatively assigned to Archaeodontosaurus descouensi., which is classified as an ‘eusauropod’; a designation that remains somewhat flexible, but typically refers to animals making the transition from Triassic prosauropods and late Jurassic-Cretaceous ‘neosauropods’. The last remaining morphotype is set into a taxon of its own (D), although the identity is largely unknown, and only tentatively proposed to be a diplodocid or basal titanosaur of some kind. It has characteristics unlike any yet seen in this formation, having a mostly peg-like shape while all other teeth are stouter with some enamel wrinkling.

Figure 2: Sauropod teeth plotted chronologically and according to dimensions measured according to figure 1. Taxa proposed in this study are shown in larger colored points and highlighted at temporal location by light blue bar.

Why is this study important? The findings in this paper imply that titanosaurs may have been around just as long as other successful groups of sauropods, like brachiosaurs and diplodocids, and that the roots of titanosaurs extends into the middle Jurassic, a time where fossils are less commonly known. Discoveries like these from this time period provide valuable insight into the changing global climate that led to the late Jurassic boom in sauropod diversity. In this case, we see the partly bipedal Triassic prosauropods slowly evolving into the large, quadrupedal animals we are more familiar with. This change is highlighted here in the shifting tooth morphology: narrower, increasingly peg-like teeth are seen as an evolutionary deviation from the more multi-purpose, wrinkled teeth associated with prosauropods. Since most later sauropods have virtually pencil-shaped teeth associated with branch-stripping and gut-digesting rather than chewing and oral-processing, the appearance of traits leaning in this direction gives us evidence that these evolutionary changes may have been propelled by competition between species and niche-filling. Accessing higher vegetation borne from trees presents pioneering animals with an untapped resource. However, trees also present challenges in the form of tough branches and leaves that are harder to digest and also often less nutritious. The transition from wider, wrinkled teeth for processing and chewing, to peg-like teeth that strip leaves from branches, allows animals to acquire more food in less time and with higher efficiency. This also translates most or all of the digestion to the stomach, which passively grinds food with the aid of gastroliths (swallowed stones), further allowing for the animal to continually take-in food and remain on the move.

The Big Picture: Special attention should be awarded to those locales which are already underrepresented in the fossil record. If one could extract new taxonomic information from less than three dozen teeth, especially from a time without significant fossil representation, then it leads one to wonder what could be found with further excavation, and the insight of local knowledge, interest, and investment. That is not to say that every sparsely researched locale is a treasure trove awaiting plentiful fossil discovery, but the matter of the Mahajanga Formation is such that its potential for producing Middle Jurassic materials should certainly not be overlooked, and is mostly untapped. The teeth used in this study were not exclusively extracted for the research of this paper. Instead, they were found as a result of a field survey conducted in tandem by an Italian institution (Museo di Storia Naturale di Milano), and a couple of Malagasy geological ministries in the early 2000s. It is only recently, in 2019 that the teeth were pulled from archives for analysis. This means that this the geological deposits near Ambondromamy, Madagascar, likely have much yet to show us.   

Citation: Bindellini, G. and Dal Sasso, C. (2021), Sauropod teeth from the Middle Jurassic of Madagascar, and the oldest record of Titanosauriformes. Pap Palaeontol, 7: 137-161. https://doi.org/10.1002/spp2.1282

Will NASA’s Dragonfly Mission Encounter Dust Devils on Titan?

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Dust Devils on Titan

Brian Jackson, Ralph D. Lorenz, Jason W. Barnes, and Michelle Szurgot

Summarized by Lisette Melendez

What data were used? In 2019, NASA announced a brand-new mission: Dragonfly. The objective? To visit Titan, the largest moon of Saturn and the only place in our universe (besides Earth) where distinct evidence of surface liquid has been discovered. Titan’s environment is very similar to that of very early Earth, with a nitrogen-rich atmosphere and volcanic activity. By studying Titan’s chemistry, scientists can discover more about the origin of life itself. It’s a very exciting mission, but it’s important for scientists to prepare for all the different obstacles the rotorcraft will encounter on Titan’s surface, including hazardous weather phenomena like dust devils.

An illustration of NASA’s Dragonfly rotorcraft-lander approaching the dunes on Saturn’s exotic moon: Titan. Credits: NASA/JHU-APL

We’ve learned more about weather patterns on Titan through NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017. This study focuses on how dust storms are identified on other celestial bodies and what implications they hold for the Dragonfly mission. Cassini identified three regional dust storms within the equator near the “Shangri-La” dune fields that were chosen as Dragonfly’s landing spot. The study of these dust storms in Titan’s unique environment (with clouds and rain of methane!) can help us learn more about how they operate and life dust in the first place. This study also draws from observations by the Huygens probe for information on Titan’s temperatures and atmosphere.

Methods: In order to determine the weather conditions necessary for a dust storm on Titan, scientists need data on various atmospheric circumstances, such as temperature, elevation, and pressure. By analyzing the images and observations collected by Cassini and Huygens and combining these findings with data collected by observing dust devils here on Earth, scientists were able to model the surface conditions that were suitable for dust devil formation as well as the size of these storms. The study focused on dust devils on the equator because that’s where we have the most data available about Titan’s weather conditions.

An illustration of the Cassini-Huygens space-research mission, which was a collaboration between NASA, the European Space Agency (ESA), and the Italian Space Agency (ISA) to study Saturn and its many moons. Credit: NASA/JPL

Results: Many of the atmosphere conditions identified on Titan are favorable for the formation of dust devils. On Earth, dust devils are generally hindered by the presence of liquid because the increased particle cohesion (i.e., how sticky the particles are to one another) prevents wind from being able to lift the dust particles. Observations show that the equator of Titan is very arid and dry, with methane downpours only occurring in areas once every 10 Earth years. By looking at surface humidity levels measured by Huygens, it shows that the surface is too dry for even cloud formation. The abundance of dunes and dust storms provides further evidence that Titan has the ideal environment for dust devils.

An image of a dust devil in Kansas. Credit: The Thunderbolts Project

However, there are some surface conditions on Titan that may reduce the occurrence of dust devils, including the possibility of insufficient wind speeds. Additional work is required to model typical speeds on Titan’s surface.

Why is this study important? This study is important because it helps predict the occurrence of dust devils on Titan when Dragonfly is scheduled to arrive in 2034. This study outlines what remains unknown about the formation of dust devils and how Dragonfly presents the opportunity to study wind-related phenomena in a novel environment.

The big picture: After analyzing the environment on the surface of Titan based on the data currently available, it is concluded that the dust devils will most likely not pose a threat to the Dragonfly rovercraft (since they are too slow in the given conditions). Nevertheless, the mission can provide crucial insight to the creation of dust devils and how frequently they occur on other celestial bodies. Dragonfly provides us the opportunity to learn so much more about extraterrestrial worlds, and we’re all very excited for its departure!

Citation: Jackson, B., Lorenz, R. D., Barnes, J.W., & Szurgot, M. (2020). Dust devils on Titan. Journal of Geophysical Research: Planets, 125, e2019JE006238. https://doi.org/10.1029/2019JE006238

Climate Change and Encephalitis

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The potential impact of climate change on the transmission risk of tick-borne encephalitis in Hungary

Kyeongah Nah, Ákos Bede-Fazekas, Attila János Trájer, and Jianhong Wu

Summarized by Kailey McCain

What data were used? The data collected for this study includes the monthly average temperature values in Hungary from the years 1961-1990. Specifically, for the past climate data,researchers used the CarpatClim-Hu database. For future climate predictions, the researchers used two distinct climate models: ALADIN-Climate 4.5 and RegCM 3.1. Additionally, previously established models for Tick-borne Encephalitis virus (i.e., a human viral infectious disease) transmission was used. Models help us hypothesize how different scenarios will look, by allowing us to input a lot of different types of data to understand large future patterns, like the one in this article! 

Methodology: By using the previous climate data for the years 1961-1990, the researchers established a predictive warming model for the years 2021-2050 and 2071-2100 in Hungary. This data was then compared to the tick-borne encephalitis virus (TBEV) transmission model to establish correlations between the data sets. This model broke down the transmission into various factors: reproduction numbers, duration of infestation, and density. The dynamics of transmission can be visualized in figure 1.

Figure 1: This figure shows an extensive diagram of how an infected tick spreads the disease to humans, livestock, and other animals. The inner circle represents the stages from larva, to nymph, to mature tick; then it branches to external transmission.

Results: The predictive climate model showed a steady increase in temperature for the age ranges 2021-2050 and 2071-2100, and the TBEV model resulted in an increase in tick population and transmission. These increases can be positively correlated (linked) to warming climate because previous data shows that a higher temperature speeds up the rate of sexual maturity in ticks; meaning, this allows the tick to reproduce at an increased rate. Moreover, research has shown that a warming climate leads to the elongation of tick questing season; which increases the chance for transmission. When a tick is questing (shown in figure 2), it is strategically placed on vegetation in order to grab a hold of by passers. 

Figure 2: This image represents a questing tick sitting on the edge of a lead with their legs spread out, and ready for attachment.

Why is this study important? This study is important because it shows the dynamic effects climate change has on global health. It also conveys an important message that the prevention of climate change is not only a biological and geological problem, but a public health problem, too. This means that solutions for reducing the impacts of climate change have to be creative and have to be from a lot of different types of researchers! 

The big picture: This study helps us understand the ways in which infectious diseases, (e.g., Tick-Borne Encephalitis Virus) are affected by climate change. As well as giving a glimpse into the future of what disease transmission will look like if prevention protocols are not put in place.

Citation: Kyeongah Nah, Ákos Bede-Fazekas, Attila János Trájer, & Jianhong Wu. (2020). The potential impact of climate change on the transmission risk of tick-borne encephalitis in Hungary. BMC Infectious Diseases, 20(1), 1–10. https://doi.org/10.1186/s12879-019-4734-4

How Climate Change in Serbia is Impacting the Rate of Cancer and Infectious Diseases

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Assessment of climate change impact on the malaria vector Anopheles hyrcanus, West Nile disease, and incidence of melanoma in the Vojvodina Province (Serbia) using data from a regional climate model 

By: Dragutin T. Mihailović, Dusan Petrić, Tamas Petrović, Ivana Hrnjaković- Cvjetković, Vladimir Djurdjevic, Emilija Nikolić-Đoric, Ilija Arsenić, Mina PetrićID, Gordan Mimić, Aleksandra Ignjatović-Cupina 

Summarized by: Kailey McCain

What data were used? Researchers assessed climate change and UV radiation (UVR) and compared it to data collected over ten years from mosquito field collections at over 166 sites across Serbia. Additionally, public health records for the circulation of vector-borne disease (I.e., illnesses spread by mosquitoes and ticks), specifically the West Nile Virus, and the incidence of melanoma (i.e., a serious form of skin cancer) were collected and compared.

Methods: The climate change and UVR doses were collected by using EBU-POM model (a type of regional climate model) for the time periods: 1961-2000 and 2001-2030. As for the collection of the mosquito data, two different dry-ice baited traps (dry-ice is a solid form of carbon dioxide, which is a natural attractive substance for mosquitos) were used. The various sites were chosen by entomologists (i.e., scientists who study insects) to obtain a diverse data set. The mosquitoes collected were then anesthetised, separated by location, species, sex, and then tested for a specific RNA (I.e., a single stranded molecule) strand that would indicate the mosquito was carrying the West Nile Virus.

Furthermore, the researchers measured the rate of melanoma incidences in Serbia by using two different indicators: new number of cases versus time and number of new cases versus population size. The defined time period for data collection was 10 years (1995-2004). With this data, the researchers compared the rate of incidence to the climate data previously collected.

Fig 1: This diagram shows the linear trend in annual temperature fluctuations throughout Serbia from the time period 1990-2030; as well as depicts the mosquito prevalence found at the various collection sites.

Results: From the data collected via the regional climate model, a linear upwards trend in temperature in Serbia was recorded. The prevalence of mosquitoes was also found to increase linearly throughout the time period. The culmination of these results can be seen in figure 1.

As for the melanoma data, the researchers found a linear increase in UVR doses for the time period. This data was found to be correlated to an increase in melanoma incidences throughout Serbia and this data can be visualized in figure 2.

Why is this study important? Disease prevalence and distribution have always been difficult to predict due to the varying ecological factors that play important roles. Research like this is especially important because it allows scientists to simulate future spreads of vector-borne diseases within European countries. This can eventually lead to the development of public health surveillance technology and overall prevention.

Fig 2: Diagram (a) depicts the increased temperature rates throughout Serbia, and diagram (b) depicts the UV radiation doses on the various provinces throughout Serbia. Diagram (c) shows the linear relationship of UV doses versus the time period 1990-2030. The data shows a clear increase in “hot days” (HD) and “warm days” (WD) through time. Diagram (d) shows a linear relationship between UVR dose versus melanoma incidence rate from 1995-2004.

The big picture: This study aimed to correlate changes in temperature and UV radiation to the spread of diseases and cancer. With vector-borne diseases being the most sensitive to ecological conditions, researchers chose the West Nile Virus to act as a proxy to all mosquito transmitted diseases. As expected, the data supports the claim that increased temperatures trigger an enhanced risk for not only infectious diseases, but certain cancers as well.

Citation: Mihailović, D. T., Petrić, D., Petrović, T., Hrnjaković-Cvjetković, I., Djurdjevic, V., Nikolić-Đorić, E., Arsenić, I., Petrić, M., Mimić, G., & Ignjatović-Ćupina, A. (2020). Assessment of climate change impact on the malaria vector Anopheles hyrcanus, West Nile disease, and incidence of melanoma in the Vojvodina Province (Serbia) using data from a regional climate model. PLoS ONE, 15(1), 1–17. https://doi.org/10.1371/journal.pone.0227679

How coastal wetlands can help reduce property damage from storm surge and sea level rise

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Valuing natural habitats for enhancing coastal resilience: Wetlands reduce property damage from storm surge and sea level rise

by: Ali Mohammad Rezaie, Jarrod Loerzel, Celso M. Ferreira

Summarized by: Mckenna Dyjak

What data were used?: This study used coastal storm surge modeling and an economic analysis to estimate the monetary value of wetland ecosystem services (positive benefits of natural communities to people). One of the ecosystem services provided by wetlands is that  they are great at controlling flooding; their flood protection value was estimated using the protected coastal wetlands and marshes near the Jacques Cousteau National Estuarine Research Reserve (JCNERR) in New Jersey. 

Methods: Storm surge flooding was determined for historical storms (e.g., Hurricane Sandy in 2012) and future storms that account for habitat migration and sea level rise. Each storm had modelled flooding scenarios for both the presence and absence of the coastal wetland/marsh. The model also incorporated ways to account for monetary value of physical damage by using property values.

Results:  This study found that coastal wetlands and marshes can reduce flood depth/damage by 14% which can save up to $13.1 to $32.1 million in property damage costs. The results suggest that one square kilometer (~0.4 square miles) of natural coastal wetland habitats have a flood protection value of $7,000 to $138,000 under future conditions (Figure 1).

Figure 1. This graph shows the estimated monetary value of coastal marshes flood protection in different storm scenarios per square kilometer. A “25 year Storm” or “50 year Storm” is a storm event that occurs once on average in the time span given.

Why is this study important?: Natural coastal wetlands and marshes contribute many vital ecosystem services such as providing habitats for wildlife, helping protect against coastal erosion, and purifying water. Assigning a monetary value to these natural habitats for their flood protection can highlight another aspect of their importance and urge people to protect these important coastal communities. The results from this study can allow the public and private sectors to develop and practice sustainable methods to preserve the ecosystems.

The bigger picture: Storm events, such as hurricanes, are predicted to become more frequent and more severe due to climate change. As the oceans continue to warm (an estimated increase of 1-4 degrees Celsius in mean global temperatures by 2100) hurricanes are predicted to intensify in wind speed and precipitation. Storm surge is known to be the most dangerous aspect of hurricanes and causes deadly flooding. As sea levels rise and ocean water expands due to warming, storm surges will become more severe during major storm events. This study has shown that coastal wetlands and marshes are considered our “first line of defense” in these circumstances. We must take care of and protect our natural habitats because they provide us with many services that we are unaware and likely unappreciative of.

Citation: Rezaie AM, Loerzel J, Ferreira CM (2020) Valuing natural habitats for enhancing coastal resilience: Wetlands reduce property damage from storm surge and sea level rise. 

How fossil collection methods can affect paleoecological datasets

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The influence of collection method on paleoecological datasets: In-place versus surface-collected fossil samples in the Pennsylvanian Finis Shale, Texas, USA

Frank L. Forcino, Emily S. Stafford

Summarized by Mckenna Dyjak

What data were used?: Two different fossil collecting methods were compared using the Pennsylvanian marine invertebrate assemblages of the Finis Shale in Texas. In-place bulk-sediment methods and surface sampling methods were used to see how these different methods could influence taxonomic (groups of animals) samples. 

Methods: The bulk-sediment sampling method involves removing a mass of sediment and later washing and sieving the material to retrieve the fossil samples; surface sampling is a simpler method in which the top layer of sediment is removed and the exposed fossils are collected by hand. The samples were collected in the Finis Shale in Texas at stratigraphically equivalent (layers of rock deposited at the same time) locations to ensure continuity in the two methods. The bulk-sediment and surface pick-up samples were analyzed for differences in composition and abundance of fossil species (i.e., paleocommunities) using PERMANOVA (a type of analysis used to test if samples differ significantly from each other).

Results: The study found that the bulk-collected samples differed from the surface-collected samples. The relative abundance of the major taxonomic groups (brachiopods and mollusks), composition, and distribution varied considerably in both collecting methods. For example, there was a higher relative abundance of brachiopods in the bulk-collected samples and a higher relative abundance of gastropods in the surface-collected samples.

Figure 1. Comparison of relative abundance of fossil groups between in-place and surface samples. Note the different abundances from each of the collection methods.
(SpE = Spillway East outcrop, SpW = Spillway West outcrop, CW = Causeway Road outcrop)

Why is this study important?: Bulk-sediment sampling and surface sampling methods produce significantly different results, which would end up affecting the overall interpretation of the history of the site. The surface-collected fossils may be influenced by stratigraphic mixing (mixing of materials from different rock layers), collector bias (which can influence a fossil’s potential to be found and collected; for example, larger fossils are more likely to be collected), and destruction of fossils due to weathering. Bulk-sediment sampling will likely have a more accurate representation of the ancient community, because the fossils likely experienced the least amount of alteration during the process of the organism becoming a fossil (also known as taphonomy).

The bigger picture: The amount of things that have to go right in order for an organism to become a fossil is a lengthy list (read more about the fossilization process here). There are many biases that can contribute to the incompleteness of the fossil record such as environments that favor preservation (e.g., low oxygen), as well as poor preservation value of soft tissues, like skin. Scientists must do what they can in order to collect accurate data of the fossil record since there are already so many natural biases. Knowing which fossil collecting methods produce the most accurate results is important when advocating for the paleocommunity.

Citation: Forcino FL, Stafford ES (2020) The influence of collection method on paleoecological datasets: In-place versus surface-collected fossil samples in the Pennsylvanian Finis Shale, Texas, USA. PLoS ONE 15(2): e0228944. https://doi.org/10.1371/journal.pone.0228944

Organic carbon stored in Florida lakes

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Organic carbon sequestration in sediments of subtropical Florida lakes

Matthew N. Waters, William F. Kenney, Mark Brenner, Benjamin C. Webster

Summarized by Mckenna Dyjak

What data were used? A broad range of Florida lakes were chosen based on size, nutrient concentrations (nitrogen and phosphorus), trophic state (amount of biologic activity that takes place), and location. The lakes were surveyed using soft sediment samples to identify the best drilling sites for sediment cores. After drilling, the cores were dated and the organic carbon (OC) content and burial rates were calculated. Organic carbon can be stored in sediments and buried, which temporarily removes it from the atmosphere.

Methods: The sediment cores were taken using a piston corer commonly used to retrieve soft sediments. Each core was dated using ²¹⁰Pb which is a common radioactive isotope found in lake environments and can be used to date sediments up to 100 years. Radioactive isotopes can be used to date rocks and sediments based on their natural decay rate (half-life). The organic carbon content of the cores was measured using a Carlo-Erba NA-1500 Elemental Analyzer which is an instrument that can determine the total carbon present in a sediment sample. To calculate the organic carbon deposition rates, the accumulation of sediment rates were multiplied by the proportion of OC found in the sediment. A recent increase of eutrophication (high amount of nutrients present in lakes) needed to be taken into account when calculating the OC deposition rate, so the sediments were divided into pre-1950 and post-1950 deposits to depict the change in industrial activity and agriculture. 

Results: The OC burial rate was highest in the shallower lakes and decreased as the depths increased (can be seen in Figure 1). This is different from the rates for temperate (mild temperatures) bodies of water, where OC burial rates decreased as the lakes got bigger. They found a 51% increase in OC burial rates in the post-1950 deposits which corresponds to the increase in eutrophication in the lakes.

Figure 1. Graph showing the correlation between depth and organic carbon (OC) burial rate. The OC burial rate increases as the depth decreases in meters.

Why is this study important? Cultural eutrophication is caused by an increase of nutrients in waterways such as phosphorus and nitrogen (commonly found in lawn fertilizers) which cause harmful algal blooms; these algal blooms remove oxygen from the water and can mess up the entire ecosystem. The lack of oxygen and harmful algal blooms can lead to habitat loss and loss of biodiversity. This study highlights the effects and severity of cultural eutrophication in Florida’s subtropical lakes.

The bigger picture: Managing carbon and removing it from the atmosphere (i.e., carbon sequestration) is an important aspect of climate mitigation. The carbon can be removed from the atmosphere and stored in places known as carbon sinks (natural environments that can absorb carbon dioxide from the atmosphere). This study shows that subtropical Florida lakes are effective carbon sinks for organic carbon that deserve to be protected from nutrient runoff that causes eutrophication.

Citation: Walters, M. N., Kenney, W. F., Brenner, M., and Webster, B. C. (2019). Organic carbon sequestration in sediments of subtropical Florida lakes. PLoS OnE 14(12), e0226273. doi: 10.1371/journal.pone.0226273