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Julie Granger, Associate Professor

Julie studied biology as an undergraduate at McGill University, where she graduated with Honours in Biology, with a focus on marine ecology. She stayed at McGill to pursued a Masters’ degree, during which she conducted research on iron-siderophore production and acquisition by heterotrophic marine bacteria in the laboratory of Dr. Neil Price. She then worked at Princeton University  as a research technician in the laboratory of Dr. Bess Ward, doing research on metal requirements of denitrifying bacteria. She returned to Canada for to pursue her doctorate, in the laboratory of Dr. Philippe Tortell at the University of British Columbia. There, she engaged in a collaboration with Dr. Daniel Sigman at Princeton University, to investigate patterns in nitrate N and O isotope fractionation during nitrate consumption by marine plankton. She returned to Princeton to conduct research as a post-doctoral fellow in Sigman’s lab, where I investigate nitrogen biogoechemical cycling on the eastern Bering Sea shelf. She became an assistant professor at the University of Connecticut in the fall of 2011, where she obtained tenure in 2017.

Current members

Michael Mathuri, Ph.D. candidate

Michael is a second year student here at UConn. He obtained an undergraduate degree in Biochemistry at Kenyatta University in Kenya and later joined M.S. Program in Geological Sciences at the University of Texas at El Paso, where he worked in Dr. Benjamin Brunner’s lab. For his master’s thesis, he used 34S and 18O isotopes to investigate sulfur cycling in marine sediments. Currently, Michael will use stable nitrogen isotopes to study the process of ammonium assimilation in cultures of marine phytoplankton.

Mengyang Zhou, Ph.D. candidate


Mengyang graduated from Nanjing University, China in July 2018 with a B.S. in Marine Sciences. During his undergraduate, he worked with Dr. Chendong Ge; using the morphology of fluid inclusions in quartz in the Yangtze River surface sediments to study sediments’ provenance. Mengyang joined the lab in August 0f 2018 and is studying the contribution of N2 fixation to new and exported production in the North Pacific Subtropical Gyre.

Veronica Rollinson, M.S. student

Veronica graduated from UConn Avery Point in May 2012 with a B.S. in Marine Science. Veronica has worked in the Marine Science Department since 2011 under Dr. Craig Tobias as a research specialist where she has assisted graduate students in field research including sampling of Niantic River Estuary, Long Island Sound, New River Estuary North Carolina, and Cape Cod Aquafer. She has lead analysis of stable isotopic composition of algal samples from St. John U.S. Virgin Islands. For her master’s project she will be studying nitrogen cycling through stable isotopic tracers for the Pawcatuck River and Little Narragansett Bay in order understand the relationship to invasive macroalgeal populations in the river. 


Josie Mottram, M.S. student


Josie graduated from St. Olaf College in May 2021 with a B.A. in biology. While at St. Olaf she work for Dr. Anne Gothmann's lab conducting a culture experiment to study the nitrogen isotopic offset between coral diet and tissue. This work brought her to UConn in the fall of 2021 where she continues to study nitrogen isotopes in corals in an effort to improve the use of corals as paleoclimate proxies.

Lija Treibergs, Research Technician,  M.S. student (2015)

Lija obtained an undergraduate degree in Geosciences at Princeton University, at which time she completed an Honors Thesis in the laboratory of Danny Sigman, conducting research on N assimilation by surface plankton at the Bermuda Atlantic Time Series (Treibergs et al. 2014). For her master’s research at UConn, Lija investigated the enzymatic isotope effects of assimilatory and dissimilatory reductases, availed commercially or isolated from model organisms. She uncovered characteristic patterns in nitrate N and O isotope fractionation shared among reductase functional groups, and further demonstrated that the amplitude of the enzymatic isotope effect varies in response to substrate and reductant concentrations (Treibergs 2015). After finishing her thesis, Lija was employed as a technical research staff at the Cory Lab at University of Michigan working on photochemical and iron redox processes impacting organic carbon degradation in arctic lakes, streams and soilwaters. Although she loved the Arctic, she missed nitrogen, the sea, and troubleshooting the IRMS, so she returned to the Granger Lab in April of 2019 after a brief stint working for the McMurdo Dry Valleys LTER in Antarctica.  

Peter Ruffino, Technical Assistant

Peter manages, maintains, and repairs our isotope ratio mass spectrometer (IRMS). He joined our lab in 2018 and spends his time split between our mass spec and Dr. Craig Tobias's.  Peter is also a Master's student in the Tobias Lab.

Reide Jacksin, Undergraduate Research Technician

Reide is a third-year undergraduate student at UConn Storrs pursuing a degree in chemistry. With that degree, she hopes to teach high school chemistry or pursue a graduate degree in atmospheric or environmental chemistry. Her main duties in the lab are sample preparation and lab maintenance.


Clare Schlink, Undergraduate Research Technician

Clare finished her courses for her undergraduate degree in Marine Science at Avery Point, she is currently working on finishing classes for a dule major in Chemistry and Marine Science. She joined the lab in the summer of 2018 under a SURF grant working on the inpact of nitrogen sediment cycling in support of the Pawcatuck River research project through CT Sea Grant.

Past Members

Lindsey Potts, Research Technician

Lindsey graduated from UCONN in May 2017 with a Bachelor's of Science in Marine Sciences. As an undergraduate, she participated in two independent studies. The first focused on potential storm-driven water temperature oscillations during the spring and summer months near the U.S Virgin Islands, under the guidance of Dr. Melanie Fewings. The second, which was advised by Dr. Claudia Koerting, explored the role of organic nitrogens, particularly urea, in macroalgae growth (Cladophora sp.) and coastal eutrophication using samples from Wequetequock Cove - a local area suffering from overwhelming blooms of Cladophora sp. In May 2017 she began work in the Granger Lab, where she is currently analyzing the nitrogen and oxygen isotope ratios of nitrate from samples taken in the Atlantic Gulf Stream to determine the contribution of nitrogen fixation in that portion of the North Atlantic Gyre.  Lindsey is also in the process of researching and developing adaptations to current methodologies for the measurement of dissolved nitrogen gas isotopes using Membrane Introduction Mass Spectrometry (MIMS). Lindsay left the Granger Lab in the fall of 2019 to pursue a Master's degree at McGill University.

Holly Westbrook, Research Technician

Holly graduated from UConn Avery Point with a B.S. in Marine Science with a minor in Chemistry in May of 2017. During her time as an undergrad she participated in a SEA Semester, which was a transatlantic crossing focusing on climate change and the global carbon cycle. She began working in the Granger lab in May 2017, where her duties involved maintenance of in situ equipment in Wequetequock Cove and sampling in the Pawcatuck River over the summer of 2017. She also currently working on an experiment regarding the δ18O to δ15N relationship during nitrate consumption in different aquatic environments, which she presented on a poster at Ocean Sciences 2018.  Holly left the Granger lab in the spring of 2019 to start a Master's in the lab of Dr. Annie Bourbonnais at the University of South Carolina.

Danielle Boshers, M.S. student (2017), Research Technician

Danielle obtained an honors B.S. in Earth and Environmental Sciences at the Univesity of Michigan, at which time she completed an Honors Thesis in Dr. Gregory Dick’s lab, conducting research on a novel Mn oxidizing bacteria. For her master’s thesis work here at UConn, Danielle is studying how the oxygen isotope composition of ambient water influences the 18O/16O of nitrate produced by nitrification, in cultures of model organisms and in freshwater environments. During her time at UConn, Danielle has conducted field work at an experimental aquifer in Cape Cod, gone on an oceanographic cruise on the RV Endeavor, and presented her research at AGU in San Francisco and Goldschmidt in Paris, France. Danielle now works as a Research Assistant at USGS Great Lakes Science Center and the University to Michigan, studying microbial symbiosis in native and non-native Phragmites.

Richard Dabundo, M.S. student (2014), Research Technician

Rich studied Geosciences at Penn State University and became interested in Geobiology. At UConn, Rich began studying N2-fixation by heterotrophic bacteria, which led him to discover that some commercial 15N2 stocks, typically used to measure N2-fixation rates, are highly contaminated with 15N-ammonium and nitrate (Dabundo et al. 2014). Following some initial despair, Rich percevered and began investingating environmental controls on the denitrification isotope effect in cultures of model organisms. He demonstrated that the isotope effect is sensitive to modulations in active cellular nitrate transport, which, in turn, appears to responds to changes in the redox state of the bacterial membrane. The redox state of the membrane can be influenced by carbon substrates, and by trace oxygenation in the medium (Dabundo 2014). Following his thesis, Rich worked as a research technician in the laboratory, and is now a mass spectrometry technician at the University of Pittsburgh.

Visiting Students and Scholars

Tanya Marshall, visiting student, Ph.D. candidate (University of Cape Town)

Tanya is a Ph.D. student supervised Dr. Sarah Fawcett at the University of Cape Town. Her research explores the nitrogen budget, including supply, removal and recycling processes across the subtropical South Atlantic Ocean. Her current focus is on the Southern and Northern Benguela water masses as well as a dataset collected from the Agulhas Current south of South Africa.

Dan Yu, visiting student, Ph.D. candidate (Xiamen University)

Dan is a Ph.D. student supervised by Prof. Huasheng Hong and Nengwang Chen in the College of the Environment and Ecology in Xiamen University in China and currently works as a visiting PhD student in Tobias’ Lab. She got her bachelor’s degree in Environment Engineering in Sichuan University in China in 2011. She then went to Xiamen University and finished her master’s thesis on greenhouse gases emissions from mangrove forest sediments in June 2014. After that she started her current Ph.D. program majoring in Environment Science. Her current research focuses on ammonium nitrogen transformation and export across the river-estuary interface, taking a subtropic estuary–Jiulong River estuary in southeast China as example.


Nadine Lehman, visiting student, Ph.D. candidate (Dalhousie University)

Nadine is a doctoral candidate at Dalhousie University in Markus Kienast’s laboratory. Nadine is measuring nitrate N and O isotope ratios in the Granger laboratory as part of the Canadian Arctic GEOTRACES program, a research project on marine biogeochemical cycles of trace elements and their isotopes. The focus of her work is the cycling of nitrogen and the geochemical modification of waters as they flow from the Pacific to the Labrador Sea. Nadine is interested in using the N and O isotopic composition of nitrate as a geochemical tracer to describe both nutrient cycling and water mass distributions in the Ocean.

Raquel Flynn, visiting student, University of Cape Town

Raquel attained a B.Sc. in Marine Biology, Oceanography and Religious Studies at the University of Cape Town. It was during her undergraduate where she discovered the world of Oceanography and started to become fascinated with the way in which the ocean works. Her Honours project focused on the rates of net primary production (NPP) and carbon export in the southern Benguela Upwelling region during the autumn of 2016. For her master's project, she is working on understanding the nitrogen cycling in the southern Benguela Upwelling region on a seasonal basis using the stable isotope of nitrate (nitrogen and oxygen).  She visited the Granger lab at the University of Connecticut to measure nitrate isotope ratios in her samples in late summer and fall of 2017.

Jason Smith, Visiting post-doctoral scholar

Jason is a rogue scientist, interested in N cycling in upwelling systems. Jason has visited the lab at UConn numerous times to make measurements of the 15N/14N of N pools in the California Upwelling, including exacting measurements of the 15N/14N of ammonium, which exists at very low concentrations at the surface ocean. His measurements are providing novel insights into seasonal N cycling, revealing an important role of nitrification in regenerating nitrate at the sea surface.

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