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A few years ago, I was studying the effects of salinity on soil greenhouse gas production and denitrification rates in coastal wetlands of Louisiana. Meanwhile, I did not know there was a saltwater intrusion (SWI) problem facing coastal agricultural systems, especially in the Lower Eastern of Maryland (LES). Saltwater intrusion occurs when saltwater moves further inland, often leaving farmlands unproductive, and possibly displacing nutrients into downstream waters (Ardón et al. 2013; Ardón et al. 2017; Tully et al. 2019). Kate Tully’s lab, among others, are looking to tackle this environmental challenge head-on. I had the pleasure of working as a research technician on this project for 8 months.
During my first day of fieldwork in the summer of 2018, I met Kate Tully and Elizabeth de la Reguera at our rental van, packed up, and drove 3 hours to the LES of Maryland for a day of plant germination and survival counting. It was about 90°F with oppressive humidity and a constant threat of mosquito and tick bites. This does not compare to latter days in the summer, with heat indexes rising closer to 106°F. Here are a few other technician duties that I typically performed:
Research Technicians play an important role in large-scale, long-term, and interdisciplinary projects like this one. I am lucky to have been able to work with such an impressive team and be in charge of coordinating the biogeochemistry analyses for an important environmental challenge. I am definitely looking back on the Good Ol’ Days with rose-colored glasses! References Ardón M, Helton AM, Scheuerell MD, Bernhardt ES (2017). Fertilizer legacies meet saltwater incursion : challenges and constraints for coastal plain wetland restoration. Elementa: Science of the Anthropocene 5:41. Ardón M, Morse JL, Colman BP, Bernhardt ES (2013). Drought-induced saltwater incursion leads to increased wetland nitrogen export. Global Change Biology 19:2976–2985. Tully KL, Weissman D, Wyner WJ, Miller J (2019). Soils in transition : saltwater intrusion alters soil chemistry in agricultural fields. Biogeochemistry. -By Natalie Ceresnak
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When we appreciate the brilliant blue of the Chesapeake Bay, salted water silently invades lands that we live on due to global warming. This phenomenon is referred as saltwater intrusion (SWI), when saline water moves into fresh aquifers and surface water. New research is showing that SWI can disrupt nutrient cycling in coastal regions (Ardón et al 2013; Ardón et al 2017). In the Lower Eastern Shore of Maryland along the Chesapeake Bay, coastal farmland is subject to severe SWI and extensive agricultural areas will be lost in the coming decades (Shepard et al 2013). These coastal farmlands and adjacent areas (i.e. forests and marshes) provide important economic, social, and environmental functions in the region (Tully et al 2019).
Don’t worry, we researchers in AgroEcoLab, are here to investigate and solve this pressing problem! My work with Dani Weissman this semester is to further investigate the impact of saltwater intrusion on nutrients (i.e. nitrogen and phosphate) in active farm fields on the Lower Eastern Shore of Maryland. By reading all research papers provided by Dani, I learned that the saltwater includes rich ionic components (i.e. sulfate, sodium, etc.) that can bind to iron in soils stimulate the release of nutrients into soil porewater and surface water (Chambers and Odum 1990). It inspired me to develop an independent summer study on answering how the ionic components of saltwater affect nutrients in soils. Thanks for this great opportunity offered by AgroEcoLab, I can experience working in a professional laboratory and apply my chemistry knowledge in practice. Until now, I have helped with sample preparation, experiment set-ups and data analysis. I still remembered the exciting moment when I obtained a perfect calibration for pipets (Figure 1); the cheerful moment when Dani and I finally resolved the instrumental issues (Figure 2). Participating in this saltwater intrusion projects not only provides me joys and self-fulfilling but also helps me develop professional research skills and enhances my understanding of environmental knowledge. My time in the AgroEcoLab is giving me an important foundation for me to attend graduate school in the future. References: Ardón M, Helton AM, Scheuerell MD, Bernhardt ES (2017) Fertilizer legacies meet saltwater incursion : challenges and constraints for coastal plain wetland restoration. Elementa: Science of the Anthropocene 5:41. doi:10.1525/elementa.236 Ardón M, Morse JL, Colman BP, Bernhardt ES (2013) Drought-induced saltwater incursion leads to increased wetland nitrogen export. Global Change Biology 19:2976–2985. doi:10.1111/gcb.12287 Chambers RM, Odum WE (1990) Porewater oxidation, dissolved phosphate and the iron curtain- Iron-phosphorus relations in tidal freshwater marshes. Biogeochemistry 10:37–52. doi:10.1007/BF00000891 Shepard A, Curson D, Patton K, Dubois N (2013) Sea-level Rise Is for the Birds: Landscape-level Conservation Planning to Protect Communities, Coastal Wetlands and Salt Marsh Birds. 20. Tully KL, Weissman D, Wyner WJ, Miller J (2019) Soils in transition : saltwater intrusion alters soil chemistry in agricultural fields. Biogeochemistry. doi:10.1007/s10533-019-00538-9 - By Tia Ouyang  Elizabeth with Toby On an uncharacteristically warm couple of days in early February, Kate, Elizabeth, and Dani attended the first annual Marsh Resilience Summit hosted by the Virginia Institute of Marine Science (VIMS) in Williamsburg, Virginia. This event was organized to bring together researchers, non-profit groups, wetland restoration practitioners, and other stakeholders to address issues related to coastal marsh restoration in the face of climate change. There was so much interest in the summit that VIMS had to move it off their campus to a nearby hotel to accommodate all the attendees. Over 200 people were present! A large portion of the event was dedicated to discussing the Chesapeake Bay Sentinel Site Cooperative. Sentinel sites are research stations where scientists measure changes in coastal ecosystems throughout the Bay. The summit was in part organized by Keryn Gedan, Assistant Professor of Biology at George Washington University and one of our very close project collaborators!
Kate gave a wonderful talk entitled Agroecosystems in transition: sea level rise and saltwater intrusion alter biogeochemical cycling in coastal farmlands and Dani and Elizabeth presented posters on their current research. Dani’s poster was on her three summers of work collecting water sample data from coastal farms, marshes, and forests. Elizabeth’s poster was on carbon fractions on farm fields undergoing saltwater intrusion. (Shout out—she won the Outstanding Student Presentation Award for her talk, based on this poster, at the annual American Geophysical Union conference). There she is below with her awesome poster and the newest little ecologist—Toby Gedan! Of course, Toby told us that he loved all of the wetland talks that Keryn took him to during the conference. The summit included many discussion-stimulating talks related to marsh migration, opportunities to enhance conservation policies, coastal community resilience, wetland ecosystem services, management and restoration techniques, dredge materials, living shorelines, and relationships between marshes, agriculture and industry. Though this summit wont be held for another few years, it certainly sparked a great amount of sharing of ideas and collaboration between people interested in protecting the marshes, in the Chesapeake Bay and worldwide! -By Dani Weissman and Elizabeth de la Reguera  Check out the new article in Civil Eats on saltwater intrusion and nutrient release from coastal farmlands.
Check out the latest publication by the AgroEcoLab! In this paper we look at the effects of sea-level rise and associated saltwater intrusion on soil chemistry in coastal farm lands. We show that saltwater intrusion dramatically alters soil chemistry, with consequences for carbon and phosphorus retention and loss. Check it out here.  This semester I’ve had the pleasure of working with Elizabeth de la Reguera and Natalie Ceresnak on different projects under the saltwater intrusion (SWI) research umbrella. Saltwater intrusion is the movement of seawater onto land and into freshwater aquifers. This phenomenon is occurring in many coastal regions, including the Maryland Eastern Shore, and can have detrimental effects on agriculture. Thankfully, researchers like Elizabeth and Natalie (and by assisting them, me) are investigating this pressing problem!
My main work with the Agroecology lab revolved around Elizabeth’s carbon fractionation work, which investigates carbon storage across a spectrum of salt concentrations and soil depths. In soils, carbon binds to other soil constituents, such as minerals and salts, to create stable assemblages within large and small soil aggregates (von Lutzow et al., 2007). Where carbon is stored plays an important role in salt-damaged farm fields because understanding the effect of sea salts on the storage and stability of carbon can help determine if these transitioning tidal wetlands on the Eastern Shore would be more valuable (in terms of carbon sequestration) than growing crops. I’ve been able to assist Elizabeth with this research by entering sample data into a massive spreadsheet, and I’ve also helped organize her 1,500 soil sample envelopes based on a certain site name, soil depth, AND particle size. My work with Natalie was also related to SWI and its impacts on soil biogeochemistry. Her research investigates how different cropping treatments affect nutrient accumulation and losses on saltwater intruded fields before, during, and after field trials. Seawater cations can compete with and replace nutrient ions (like ammonium) by binding to soil particles, and fields inundated with saltwater can thus lose these nutrients (Steinmuller & Chambers, 2018). Using samples from the same sites as Elizabeth’s, a colorimeter will soon be used to measure nitrate, ammonium, and phosphate to see if this is occurring on the Eastern Shore. Electrical conductivity (as a proxy for salinity) will also be measured to see where in the field and at what depth we find to be saltiest. When I started working in the Agroecology lab, I had only a general idea about saltwater intrusion, but I now have a better understanding of how serious a problem it is for agriculture. From working with both of these projects, I’ve learned that SWI can affect all aspects of soil chemistry and crop health in ag fields right here on our coasts. My work in the lab has helped hone my organizational skills and has taught me that soils research requires careful and precise work. It’s been a great opportunity to work in the Agroecology lab and to be a part of such important ag research! - By Taylor Brinks References Steinmuller, H., & Chambers, L. (2018). Can Saltwater Intrusion Accelerate Nutrient Export from Freshwater Wetland Soils? An Experimental Approach. Soil Science Society of America Journal,82(1). von Lützow, M., Kögel-Knabner, I., Ekschmitt, K., Flessa, H., Guggenberger, G., Matzner, E., & Marschner, B. (2007). SOM fractionation methods: relevance to functional pools and to stabilization mechanisms. Soil Biology and Biochemistry, 39(9), 2183-2207.
This fall I started working in the Agroecology lab, helping with Elizabeth de la Reguera’s study investigating the effects of saltwater intrusion on agricultural land. Hundreds of soil samples were acquired, before my time, from sites located on the Lower Eastern Shore of Maryland to test for carbon storage potential. These field samples were separated into aggregate size classes by sequentially wet sieving, a process called carbon fractionation (Six et al., 2000). The samples were then ready to be oven dried for several days.
After oven drying the aggregate sizes, I began to work with the samples. My first weeks in the lab revolved around scraping the dried soil from their tins into coin envelopes to be used later. If you saw me in the lab around this point in time you would’ve saw a seemingly never-ending mountain of tins that I’d be chipping away at, needless to say I never had to worry about having nothing to do. In addition to scraping the tins, I eventually began to prepare and measure a small amount of soil from these coin envelopes to be used for carbon and nitrogen analysis. In a broader context, I learned from this study that not only is the amount of carbon in soil important for agricultural purposes, but where that carbon is located is just as important. I found that carbon inside of macroaggregates, which is broken down easier, tends to be more labile and can be used by crops more readily than carbon located in microaggregates (John et al., 2005). Most days I would work individually in the lab, but that does not mean that there is no team chemistry on this project. Elizabeth communicates with me on a regular basis to ensure that I understand what is currently going on. Additionally, Dr. Tully and others in the Agroecology lab encourage me to come forward if I have any questions. This individualistic yet team-rooted environment is one of my favorite things about working in the lab and makes me excited to continue learning new things and helping on this project! - By Zach Johnson References John, B., Yamashita, T., Ludwig, B., & Flessa, H. (2005). Storage of organic carbon in aggregate and density fractions of silty soils under different types of land use. Geoderma, 128(1-2), 63-79. Six, J., Paustian, K., Elliott, E. T., & Combrink, C. (2000). Soil structure and organic matter I. Distribution of aggregate-size classes and aggregate-associated carbon. Soil Science Society of America Journal, 64(2), 681-689.  Filtering porewater collected from a salt-intruded field before chemical analysis. Saltwater – it belongs in the ocean, right? Well, sort of. Saltwater can move inland through flooding during high tides or through the shallow groundwater table. This phenomenon is known as saltwater intrusion, is increasing in frequency as sea levels rise. This can cause big issues in areas like Maryland’s Eastern Shore communities, where farms line the coasts. These farms grow crops which can only handle so much salt, but as more saltwater silently creeps into these fields, these crop’s tolerances are exceeded, killing them. This salt-death can be caused by the drying out of plant roots (Ardón et al, 2017). In the Agroecology lab we want to tackle the issues saltwater intrusion causes on these coastal farms. Cover crops are crops planted during the off-season that cycle nutrients found in the soil, preventing them from leaching away through rainwater. Cover crops can be used to lessen the amount of nutrients that escape these agricultural systems, combating the impacts saltwater intrusion may have on coastal farms (Gómez et al, 2009). Through the proper planting of select cover crops, farms in places like the Eastern Shore may stay in business longer, but it’s going to take some research to figure out the secret formula.
Observing cover crop impact requires lab work. For me, this means working in two places, the greenhouse and the Plant Sciences building. While at the greenhouse, I sort and filter porewater samples. Porewater is water that is found between the small spaces between soil particles, which have been collected from farm soils on the Lower Eastern Shore of Maryland that may be influenced by saltwater intrusion. At the Plant Sciences building, Dani Weissman and Natalie Ceresnak run filtered samples on a colorimeter to detect nitrogen and phosphorus levels, while another sample is used to measure pH, salinity, and conductivity. Soil chemistry plays a direct role in the development of planted crops, and by studying the chemical content of these samples we can find how to properly mitigate the impacts of saltwater intrusion. References Ardón, M., Helton, A. M., Scheuerell, M. D., & Bernhardt, E. S. (2017). Fertilizer legacies meet saltwater incursion: Challenges and constraints for coastal plain wetland restoration. Elementa, 5(0), 41. doi:10.1525/elementa.236 Gómez, J. A., Guzmán, M., Giráldez, J. V., & Fereres, E. (2009). The influence of cover crops and tillage on water and sediment yield, and on nutrient, and organic matter losses in an olive orchard on a sandy loam soil. Soil and Tillage Research,106(1), 137-144. doi:10.1016/j.still.2009.04.008 - By Ethan Glaudemans  Preparing to run water samples for pH and electrical conductivity. If you have been in the lab over the past month when I’ve been working with Dani Weissman’s water samples from various agricultural plots along the Eastern Shore, you most likely walked into the awful smell of rotten eggs. This smell comes from bacteria that thrive in low oxygen environments and feed on small amounts of sulfur that is present within the water in places such as agricultural ditches. Although these samples are not necessarily pleasant to work with, they are important when considering the long-term project that Dani has been working on since 2016. We are analyzing these samples to examine the levels of nitrogen (N) and phosphorus (P) loading in the Chesapeake Bay estuary in response to saltwater intrusion. These studies of coastal agricultural communities are extremely important as they are the leading edge of climate change. The intrusion of saltwater from rising sea levels and coastal flooding can cause an unpredictable source of nutrients (N & P) to waterways along the Eastern Shore. Past applications of N and P on farms are remobilized by the intruding waters, which is the main source of the nutrients. The lab work that I am helping Dani with this semester, coupled with the past two years of data, will be used to help illustrate the effect of saltwater intrusion on our coastlines.
My experience in the lab so far this semester has been very informative and interesting. I have learned many things up to this point and anticipate learning many more. At the beginning of the semester, I measured out samples for dissolved organic phosphate, which Dani then ran on the flow-injection colorimeter. I’ve also learned how to run a standard curve and have had a chance to help run the atomic absorption spectrometer. As of late, I have been analyzing water samples for electrical conductivity and pH and preparing more samples for P measurements. This has all been valuable information that I will use in the future. As it is still rather early in the semester, there is plenty of time and opportunity to learn new things and to continue helping Dani with her project! - By Kenny Polk References Ardón, M., A. M. Helton, M. D. Scheuerell, and E. S. Bernhardt. 2017. Fertilizer legacies meet saltwater incursion: challenges and constraints for coastal plain wetland restoration. Elementa Science of the Anthropocene 5: 41. Hartzell, J. L., and T. E. Jordan. 2010. Shifts in the relative availability of phosphorus and nitrogen along estuarine salinity gradients. Biogeochemistry 107:489–500.  The AgroEcoLab is seeking a PhD student to work on our saltwater intrusion project! See all details and how to apply here.
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