Academy of Natural Science - Research Day, December 5, 2024
"Methods Comparison for Assessing Ocean Acidification Through Pteropods"
Type of Presentation: Talk-style? I presented on stage at the Academy's auditorium
Opening
Thank you, ____. My name is Maven Mercado, and I am a fourth-year environmental science student here at Drexel. I am here to talk about some of the research I am involved in at the Invertebrate Paleontology department.
Introduction
One of the effects of climate change is ocean acidification. Our oceans absorb about a third of all anthropogenic carbon dioxide, so an increase in carbon dioxide in the atmosphere leads to an increase in carbon dioxide absorbed. This reduces the pH of the ocean and reduces calcification rates in calcifying organisms, such as mollusks and corals. These organisms use calcium carbonate to build their skeletal structures. Two species of calcium carbonate are aragonite and calcite. The former is the more soluble of the two, making organisms that utilize aragonite over calcite more vulnerable to the effects of ocean acidification and thus more valuable as bioindicators of ocean acidification. One of these aragonite-dependent organisms are pteropods, which are teeny tiny mollusks that are known as “sea butterflies”. Pteropods are commonly used as bioindicators of ocean acidification since they will display symptoms earlier than most other organisms. While there are many studies that use them for this purpose, there are few studies that look at the efficacy of different dissolution analysis methods. This research looks at dissolution trends among three species of pteropods from different ocean systems to increase accessibility of this work to groups with less funding availability and more time constraints.
Dissolution Analysis Methods
We looked at three commonly used metrics for analyzing pteropod shells: the Limacina Dissolution Index (or LDX), the Scanning Electron Microscopy (or SEM) Dissolution Index, and micro-Computed Tomography (or CT) thickness heatmaps. LDX is a semi-quantitative method that places pteropods shells on a scale of 0-4 based on their luster and opacity, where 0 is pristine and 4 is highly dissolved. It requires the least amount of training, time, and money to use effectively. This scale can be seen here, where the shells in this image get more dissolved as we move from left to right. SEM is a fully quantitative method that ranks shells on similar sort of scale based on the surface layer and the underlying shell layer. This scale is represented at the bottom of this slide, where patches of dissolution become increasingly severe moving from left to right. CT data was used to create heat maps that visualized shell thickness, with the idea that more dissolved areas may be thinner than pristine areas. In the graphic at the upper right, blue represents the thickest shell material and red represents the thinnest shell material.
These three methods vary drastically in terms of their costs. LDX would technically add no additional equipment costs since all that is needed to utilize this scale is a standard light microscope, which facilities that undergo this kind of monitoring would already have. The other two methods rely on higher resolution technology (scanning electron microscopy and computed tomography) that would have a hefty cost per specimen examined, as well as the possible licensing costs for the relevant 3D visualization software used to create thickness heat maps.
Prevailing Methods
We found that LDX and SEM are highly correlated, which means that LDX can be used as a more cost- and time-effective substitute. This is in the graphs, where each species showed a strong relationship between what percentage pristine shell is present and what LDX rank that shell was given. However, due to its high resolution, we do recommend using SEM to analyze minor and very specific areas of a shell. In the figure on the left, the blue arrows indicate dissolution that is seen throughout all methods, while the red arrows indicate dissolution that does not show up in the thickness heat map. Due to this, CT wasn’t found to be an effective method to look at pteropod shell dissolution since it only presented extreme dissolution. However, in other studies, CT has been found to be effective at looking at other impacts of ocean acidification on pteropod shells, such as rate of calcification.
Conclusions, Future Work, & Acknowledgements
This table summarizes the cost and time per specimen we found for each analysis tool. This is ongoing work. Ultimately, we would like to promote these methods to make this kind of ocean monitoring more accessible to people who aren’t pteropod specialists. Some of our future work includes developing a manual that can be used to visually compare pteropod dissolution state, looking into more quantitative methods that would be as accessible as LDX, and expanding our sample size to further analyze SEM best practices.
And that’s all I have. I would like to thank everyone on this list who has helped on various aspects of this research. I am happy to take questions if there are any, thank you.
"Methods Comparison for Assessing Ocean Acidification Through Pteropods"
Type of Presentation: Talk-style? I presented on stage at the Academy's auditorium
Opening
Thank you, ____. My name is Maven Mercado, and I am a fourth-year environmental science student here at Drexel. I am here to talk about some of the research I am involved in at the Invertebrate Paleontology department.
Introduction
One of the effects of climate change is ocean acidification. Our oceans absorb about a third of all anthropogenic carbon dioxide, so an increase in carbon dioxide in the atmosphere leads to an increase in carbon dioxide absorbed. This reduces the pH of the ocean and reduces calcification rates in calcifying organisms, such as mollusks and corals. These organisms use calcium carbonate to build their skeletal structures. Two species of calcium carbonate are aragonite and calcite. The former is the more soluble of the two, making organisms that utilize aragonite over calcite more vulnerable to the effects of ocean acidification and thus more valuable as bioindicators of ocean acidification. One of these aragonite-dependent organisms are pteropods, which are teeny tiny mollusks that are known as “sea butterflies”. Pteropods are commonly used as bioindicators of ocean acidification since they will display symptoms earlier than most other organisms. While there are many studies that use them for this purpose, there are few studies that look at the efficacy of different dissolution analysis methods. This research looks at dissolution trends among three species of pteropods from different ocean systems to increase accessibility of this work to groups with less funding availability and more time constraints.
Dissolution Analysis Methods
We looked at three commonly used metrics for analyzing pteropod shells: the Limacina Dissolution Index (or LDX), the Scanning Electron Microscopy (or SEM) Dissolution Index, and micro-Computed Tomography (or CT) thickness heatmaps. LDX is a semi-quantitative method that places pteropods shells on a scale of 0-4 based on their luster and opacity, where 0 is pristine and 4 is highly dissolved. It requires the least amount of training, time, and money to use effectively. This scale can be seen here, where the shells in this image get more dissolved as we move from left to right. SEM is a fully quantitative method that ranks shells on similar sort of scale based on the surface layer and the underlying shell layer. This scale is represented at the bottom of this slide, where patches of dissolution become increasingly severe moving from left to right. CT data was used to create heat maps that visualized shell thickness, with the idea that more dissolved areas may be thinner than pristine areas. In the graphic at the upper right, blue represents the thickest shell material and red represents the thinnest shell material.
These three methods vary drastically in terms of their costs. LDX would technically add no additional equipment costs since all that is needed to utilize this scale is a standard light microscope, which facilities that undergo this kind of monitoring would already have. The other two methods rely on higher resolution technology (scanning electron microscopy and computed tomography) that would have a hefty cost per specimen examined, as well as the possible licensing costs for the relevant 3D visualization software used to create thickness heat maps.
Prevailing Methods
We found that LDX and SEM are highly correlated, which means that LDX can be used as a more cost- and time-effective substitute. This is in the graphs, where each species showed a strong relationship between what percentage pristine shell is present and what LDX rank that shell was given. However, due to its high resolution, we do recommend using SEM to analyze minor and very specific areas of a shell. In the figure on the left, the blue arrows indicate dissolution that is seen throughout all methods, while the red arrows indicate dissolution that does not show up in the thickness heat map. Due to this, CT wasn’t found to be an effective method to look at pteropod shell dissolution since it only presented extreme dissolution. However, in other studies, CT has been found to be effective at looking at other impacts of ocean acidification on pteropod shells, such as rate of calcification.
Conclusions, Future Work, & Acknowledgements
This table summarizes the cost and time per specimen we found for each analysis tool. This is ongoing work. Ultimately, we would like to promote these methods to make this kind of ocean monitoring more accessible to people who aren’t pteropod specialists. Some of our future work includes developing a manual that can be used to visually compare pteropod dissolution state, looking into more quantitative methods that would be as accessible as LDX, and expanding our sample size to further analyze SEM best practices.
And that’s all I have. I would like to thank everyone on this list who has helped on various aspects of this research. I am happy to take questions if there are any, thank you.