Leena's Blog

Blog Post #1

I am really excited to return as an intern for a second summer with Professor Dunbar's lab group! I am continuing to work with two graduate students - Neil Tangri and Sverre LeRoy - in the Stable Isotope Geochemistry Lab.

"Sverre, Neil, and I - taking a photo break with the mass spectrometers: "

Sverre studies climate change in the mid to high latitudes of the Southern Hemisphere. She analyzes the O, C, and N isotopes from lake sediment cores from Patagonia to try to reconstruct the environmental conditions around and within the lake (e.g., wind patterns, biological productivity, etc.) over the past 10,000 years. Neil uses isotopic data from coral cores from American Samoa to determine climate conditions over the past few hundred years. Both Sverre's and Neil's research have a parallel - they use paleoclimatology, the study of changes in the past climate through the use of natural proxies that contain climate records. In Sverre's case, the sediment cores function as proxies, because they contain isotopic data at each layer, recording geochemical conditions for thousands of years. Similarly, Neil's coral cores are climate proxies. I continue to find it fascinating how isotopes, a topic I studied in my chemistry honors class last year, can be used to generate knowledge about our planet's history. Due to their differences in atomic mass, isotopes of the same element pass through physical and chemical processes at different rates - resulting in a quantifiable fractionation of the isotopes. By comparing their samples' ratios to a standard ratio, Sverre and Neil can predict environmental conditions at the time the samples formed, such as the amount of evaporation, precipitation, and organic/inorganic productivity.

Last year, I primarily worked with Sverre, helping collect isotope data from some of the sediment cores. My previous work in the lab centered on cutting samples of sediment from the core, grinding the sediment, preparing samples for the mass spectrometers, and entering data into Sverre's large spreadsheets. In addition to developing a first-hand understanding of the tedious, yet essential, process of scientific data collection, I read and discussed scientific papers with Sverre and other interns in our lab to gain a broad understanding of the field of Earth Sciences. I also enjoyed observing and experiencing the life of grad students, attending a few dissertation defenses, and participating in grad student "hunts" for free food.

Though I will continue to assist Sverre with her research this summer, I will mainly be working with Neil, who is developing an age model for coral cores. Though coral grows in annual bands that are usually distinct under UV light, it is not always possible to accurately determine the age of samples by counting the bands, which appear vague in certain areas. Neil will combine oxygen, carbon, and annual density band data to develop an age model for the coral core. I look forward to using R, a statistical programming language, and SMAK, an analysis toolkit, to analyze the isotope data!

From the papers I have read over the past two weeks, the interpretation of isotope data to reconstruct climate conditions seems relatively complicated - it's all very well to understand what each isotopic ratio "might" signify, but piecing together all the information from different sources requires more than a purely geochemical understanding. In addition, a scientist's data rarely comes out in a perfect line exhibiting the trend he or she expects to observe. Both Neil and Sverre's data are a collection of jagged lines with some distinct peaks and troughs. I am beginning to see the prominent role that statistics and modeling has to play in interpreting various sources of data and finding correlations. This summer, I am looking forward to developing a deeper understanding of scientific modeling and data analysis.

Apart from my work in the lab, I am looking forward to the intern activities this summer. Our visit to Hoover Tower was really fun, as were our Wednesday meetings. It was interesting to hear the experiences of the two graduate students who came to speak about their research and steps leading up to grad school. I look forward to learning about the other interns' experiences.

Blog Post #2

The past few weeks of the internship have gone by quickly! A highlight was our field trip to the Hopkins Marine Station. At the tide pools we examined a variety of organisms, including turban snails, mussels, green anemones, barnacles, sea urchins, and shore crabs. We were there as the tide was rising and observed the water levels gradually submerging tide pools at various altitudes. After an engaging lecture by Professor Francis about his research on nitrogen cycling, we got to tour the facility and see some of the labs.

My work in the geochemistry lab is progressing as a project focused on the analysis of a lake sediment core from Lago Sarmiento, located in Torres del Paine National Park in Patagonia. This region, the primary land mass located in the path of the Southern Westerly Winds, is important for paleoclimate studies. Past research in the lab has included isotopic tests on the carbonate in the bulk sediment samples of this core. The composition of the bulk sediment consists of two sources – authigenic and biogenic material, differentiable by particle size. Authigenic sedimentation occurs largely as a result of hydrological factors such as evaporation and precipitation. Biogenic material in carbonate comes primarily from the skeletal remains of organisms and is impacted by vital effects of the organisms, in addition to the hydrological conditions of the time. I will be collaborating with another intern, Tom, to compare and analyze the isotopic data from the authigenic, biogenic, and bulk sediment, to reconstruct the environmental conditions of the area since the beginning of the Holocene Era.

The lab work for this project involves many steps – I have to first separate the authigenic and biogenic sediment samples from the bulk sediment and then run tests on the samples. Our challenge last week was designing the sieving process to separate the bulk sediment. The sediment was spread on a micron sieve mesh and washed with nanopure water. Sediment was sieved at 63 microns to obtain authigenic sediment and 150 microns to obtain biogenic sediment. The resulting sediment samples were placed in the oven to allow the water to evaporate. I look forward to using the mass spectrometers to analyze these samples.

"Stages of sample preparation include cutting core samples at each cm of depth, freeze-drying the bagged samples, sieving, and drying in the oven: "

"Mass Spectrometer: "

Blog Post #3

This blog post is a reflection of the last few weeks of the internship.

The very last week has been the most exciting one. A highlight was giving a tour of Professor Dunbar’s Stable Isotope Biogeochemistry Lab to the rest of the interns, viewing the labs the other interns worked in over this summer, and taking a tour of the farm where some interns had their projects. It was interesting to see the different environments and learn about the projects that others had been engaged in.

Me giving a lab tour to other interns:

As I completed my laboratory tasks, I worked in parallel on completing a scientific poster to broadly outline Sverre’s research and my summer involvement and learning on this project. I presented the research and my internship experience to the other interns and internship supervisors at the final event on August 5^th. I plan to present this poster to the Environmental Club at my high school in the coming year to motivate other students with STEM research interests to explore this program.

This summer, I learned about the challenges that interest Earth Science researchers, I participated in the process of scientific research, and I engaged in the life of scholars in an academic institution. I observed, from the talks by various professors and graduate students, how a multi-disciplinary area of study addresses a wide range of problems by applying chemistry, physics, biology, mathematics, computer science, and economics to generate scientific knowledge and engineer solutions.

My work in the lab taught me that precision, repetition, patience, and resilience are necessary to be a successful researcher. I saw first-hand the difficulties in working with complex machines. A few of our mass spectrometers were malfunctioning over this summer, a source of great stress (and emotional bonding) among the graduate students who were dependent on the machines. Lab lunches, paper discussions, and analysis of data with Sverre and Neil made me feel like a part of their research group. Sverre also introduced me to the book Paleolimnology by Professor Andrew Cohen, as well as various scientific articles, which gave me a deeper understanding of her research area.

While I do not yet know which specific field of scientific problems I will work on in the future, I end this summer motivated to study STEM and contribute to scientific knowledge that can be applied to multi-disciplinary efforts to solve the problems that face our world.

I thank Jenny and Megan for making this summer program an invaluable learning and social experience. I am grateful to Sverre, Neil, and Dave for welcoming me back into their research group for a second summer and spending time supervising and educating me. The other Earth Science Interns made this summer fun and memorable – thank you all!

My research poster: