We have meddled with the primal forces of nature.
Humans, through the migration of populations, agricultural practices and fossil fuel consumption have interfered with the natural carbon cycle of the planet, yielding significant consequences. But it’s a complicated ebb and flow, a tidal gravity, and an ecological balance that is transforming the planet.
Environmental chemist Juliana D’Andrilli, Ph.D., is a researcher and Assistant Professor at the Louisiana Universities Marine Consortium in Chauvin at the edge of the Gulf of Mexico. Her goal is to understand the Earth’s carbon history, current status, and from there, forecast its future through the migration and transformation of carbon-based materials in the ecosphere.
“That’s a really important piece of a puzzle wherever you live on this planet, but it can also aid in understanding carbon materials on other planets,” she said.
Unlocking a lot of the mysteries of Earth's past can come from studying ice cores, and the time is now to understand our history before the ice sheets diminish completely. And as we think about the records stored and ice cores, we're not only interested in what the Earth was like in the past, but also how the ice is changing now, and what these records might help us understand in the future.
D'Andrilli at the Desert Research Institute, in Reno, Nevada, while working in the ice core melting freezer (-20 degrees C) within the laboratory of Dr. Joseph R. McConnell. The ice core contains a visual thick ash layer from a lot of volcanic activity. The ice core was cataloged at ~2700 meters below the ice surface and is dated ~27,000 years ago (D’Andrilli et al., 2017).[i]
Fluorescence spectroscopy has been instrumental in answering Earth history questions in her lab.
“Thankfully, fluorescence is really sensitive, so I can do a lot with a little, and I've been able to measure organics in ice from about 27,000 years ago using this technique,“ she said.
And the trends she’s uncovered in those ice samples, those historical chemical records, are revealing.
“I’ve seen trends of different types of carbon based materials being produced in different climate periods. So, this tells me that the Earth was functioning differently when the climate was different and as temperature changed, we have changes in carbon productivity over time, therefore different types of materials were interacting with the atmosphere in the past. These are the materials that get transported to the poles and get deposited on our ice sheets before they become encapsulated and preserved in our ice systems.”
Knowing the past gives us great insight into our current conditions and perhaps what’s to come. If we don’t know where we came from, we can’t know where we’re going, according to D'Andrilli.
We’re all made of carbon and all Earth’s organisms are carbon-based. So, thinking about what materials are produced, how they are transformed, and how the Earth cycles its materials is essential. As the Earth’s biosphere reservoirs are connected, she works with materials that cycle continuously to determine its role and fate in the environment.
When she says things like organic carbon recycling and transformations, she’s talking about measuring a starting material or organic compound and then following it to an end product from the transformation. Her research focuses on how microscopic organics are built in ecosystems, how it goes through different food webs, how microbes use it, how it gets oxidized by the sun, and then if it turns into greenhouse gases once transformed.
Organic cycling leads to inorganic carbon products like carbon dioxide, and while D'Andrilli focuses on characterizing the organic constituents first, she always ties in what products come out on the other end of the cycle.
A self-described eclectic environmental chemist, she doesn’t discriminate based on her surroundings.
“I conduct organic carbon surveys in ecosystems wherever I can,” she said. Her research spans polar environments, but she also studies aquatic and terrestrial ecosystems, at lower latitudes including rivers, lakes, marine waters, soils, and precipitation.
“I love to engulf myself in understanding the fundamental processes that govern carbon transformations or microscopic organic material in any ecosystem. That's going to tell us about how the Earth functions, but it also is going to provide an opportunity to catalog fluorescence carbon signatures worldwide that we can then use when surveying life on other planetary bodies.”
Like that happening now on Mars.
Fluorescence spectroscopy is a key component of D'Andrilli’s research. Tops on the list is its sensitivity when used for low carbon environments. She doesn’t always get large samples, particularly from ice cores. But because fluorescence is so sensitive, she only needs small sample volumes to conduct her research.
“My favorite expression with fluorescence spectroscopy is doing a lot with a little, so having small sample volumes and having a very specific, sensitive instrument that can target different types of chemical constituents gives me the most bang for my buck,” she said. “I can start teasing apart chemicals, species, and characteristic organic components at that level, using an instrument that doesn't ask a lot. I don't have to load 10-30 liters of water into a container and haul it somewhere else to do the measurements.”
“It also means my work can be highly collaborative. For example, ice core research. We have to do a lot with a little because we only get certain pieces of the main ice core drilled, and we're sharing it with laboratories from around the world. Everybody's given a piece, everybody wants to ask a question, and we are all given a finite amount. A lot of ice core researchers ask, ‘What can you do with small sample volumes?’ I respond with, I'm going to shine some light through it, and I’ll see what types of chemical signatures can be discerned from the data. Once all the data is collected, patterns begin to emerge, and the story comes together. Even having a few milliliters of sample can reveal an enormous amount of carbon data.”
Plus, with fluorescence spectroscopy characterizing aquatic carbon materials through signatures on this planet, then we have created a catalog of signatures to use for comparison on Mars, and perhaps one day the ocean covered Jupiter moon of Europa. We might find the same chemical species that we’ve catalogued through research like D'Andrilli’s. And it will better inform us on what types of chemistries exist on other heavenly bodies.
D'Andrilli focuses on dissolved organic matter (DOM), because it is the largest reactive pool of carbon on the planet. DOM is microscopic, and exists at the bottom of the food chain, i.e., the smallest size of material that can undergo carbon transformations while providing energy to organisms. However, it plays an integral role that can feed higher structures in our ecosystems.
For example, DOM provides energy to certain microorganisms that then influence other organisms and processes higher and higher up the food chain to fish communities and humans.
“It basically feeds everything on this planet,” she said. “We cannot live without organic materials. So, the thesis of existence begins at the dissolved level.”
D'Andrilli began her career working with the FluoroMax-4, which is still her favorite version of Horiba’s fluorescence instruments developed to generate Excitation Emission Matrices.
“The FluoroMax-4, I love, because it’s the most sensitive for low carbon environmental work,” she said.
She currently has an Aqualog in her lab, a smaller benchtop spectrofluorometer that can be taken to research field sites. The Aqualog produces results in seconds, using proprietary A-TEEM ― Absorbance, transmission, fluorescence excitation emission matrixes ― in one measurement, correcting for the inner filter effect and producing more accurate results than without the correction.
Her research program in Louisiana focuses on developing relationships with environments that aren’t easily accessed and bringing education to local communities
“Everybody in Louisiana knows that sea level is rising,” she says. “We walk out our back doors in Louisiana and see the Gulf of Mexico rising each day.”
Her job is to connect what's happening in distant environments connected through ocean water movements with what people experience locally. The carbon materials released from the ice sheets in the Arctic may follow two mechanisms that lead to changes in the environment. One involves reacting, in which its chemistry is changed through biotic or abiotic processes and the other is movement pathways, in which materials may sink to the bottom of the ocean and settle in the sediments or flow through the global conveyor belt of the ocean. Through these processes, we have a great opportunity to connect to the materials that meets us at our back doors.
“What types of organics are these ice sheets and waters?” she asks. “And what are they going to do?”
To understand the effect of organic carbon on the carbon cycle from ice sheets to our backdoors, we have to know what materials are being released (melting) in the Arctic, how they transform, whom they affect, and where they are going.
There's a down slope gradient on Arctic ice sheets. Newly melted materials are going to flow into adjacent water bodies and then mix in coastal zones. Her headquarters in Louisiana is a coastal ecosystem that eventually receives recycled and transported materials from distant environments. The ice sheets have their own coastal ecosystems. It’s a long journey. The same materials that melted at the ice sheet surfaces are not necessarily the ones that persist in the ocean or meet us at lower latitudes. It’s the products of the carbon transformations on the ice, during its journey to the coast that will shape what happens in local marine waters and then the products of subsequent transformations in those waters that determine what happens to it next.
“If we track the types of transformations that are occurring at these different stages, then we can understand how the next ecosystems will be influenced and what end products of those processes will make it through our global conveyor belt and meet us at our back door,” she noted. This is true in both polar regions as ocean water cycles its way around the world.
Different types of carbon species are going to affect different microbial communities and other organisms along the way. The melting/calving of the ice sheets and subsequent depositing of carbon materials in the oceans and transformation products released to the atmosphere have consequences, some lead to dramatic changes in the environment.
“If we know what kind of carbon is going to be transformed and what those end-products are, then we can predict how they're going to influence their adjacent ecosystems,” she said.
A lot of people think the dissolved organic material we can’t see as humans are recalcitrant and never going to react in the environment. But as temperatures rise with climate warming, ecosystems change, thus creating different speeds or mechanisms of transformation when dissolved carbon species reach a new environment. For example, carbon dioxide (CO2) concentrations may increase if more materials are available for transformation, i.e., something that didn’t regularly transform in its current state, gets processed as its ecosystem changes (like ice sheet carbon reacting as it melts).
These are natural processes, and although increases in CO2 concentrations in the atmosphere is changing conditions on the planet, it’s all part of a transforming ecological balance.
“Carbon cycling is a natural process,” she emphasized. “Exacerbated cycling from harmful activities, such as the burning of fossil fuels creates an entirely other component of studying carbon cycling. The burning of fossil fuels are changing our ecosystems drastically; as temperatures rise with increasing CO2 concentrations in the atmosphere, we're headed towards irreversible change.”
The effects of temperature rise from the burning of fossil fuels can be seen as ice sheets continue to melt, shrink, and retreat without replacement. This means the climate is warming faster than the snowfall can continue to replenish the ice sheet systems. Studying CO2 outgassing from natural carbon processes, such as those described from organic matter released from ice sheets, is very important because as of yet, we don’t know how large a contribution it will be to our atmosphere. The time is now to study what types of organic materials may lead to pivotal impacts that are scalable across our large frozen Arctic and Antarctic reservoirs.
D’Andrilli’s research continues to focus on understanding microscopic carbon-based materials in a variety of ecosystems, using fluorescence to determine different organic matter origins and transformations that occur in aquatic networks. She makes connections across hydrologically linked aquatic ecosystems with changing variables such as, time, sunlight exposure, temperature, and moisture. Imagine following a raindrop or parcel of water throughout its journey in the Mississippi River Basin or that section of ice melted at the ice sheet surface and traveling to the ocean. Understanding the materials and how it changes or moves throughout aquatic, terrestrial, and/or atmospheric compartments is always the first step. The next step comes with understanding what happens as our ecosystems undergo irreversible changes, such as global temperature rise. This is an important next step as we make predictions for our future.
”I see increased carbon transformations over the next 10 to 20 years as temperatures rise,” she said. “I see ecosystems functioning, with higher productivity in warmer temperatures. We've been looking at historical trends of the Earth, how it worked in colder temperatures (> 20,000 years ago) through deglaciation to warmer temperatures (~12,000 years ago to today). We see signatures of more carbon productivity when the temperatures increased. I see that continuing as our greenhouse gases increase and warming continues on Earth. I see ice sheets diminishing and the oceans changing. I see river carbon production, surface ocean carbon production, and coastal zone carbon production increasing. Likely, our surface biospheres and atmosphere will be richer with organic carbon getting cycled throughout the world. Where it is going to go and what it is going to do when it gets there is what fascinates me. From my perspective, having the tools to measure and understand carbon changes is the key.”
Now, new research questions are forming with diminishing ice sheets. They have and continue to serve as records of our past, but with increasing temperatures, now, can be considered important reservoirs of potentially impactful carbon once they retreat. How will the oceans respond to their inputs? D’Andrilli is eager to learn, equipped with her Aqualog and 10-year catalog of fluorescence signatures acquired from around the world.
1 D'Andrilli J, Foreman CM, Sigl M, Priscu JC and McConnell JR (2017) A 21 000-year record of fluorescent organic matter markers in the WAIS Divide ice core. Climate of the Past, 13(5), 533-544 (doi:10.5194/cp-13-533-2017)
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