Research
Research Interests
I study biogeochemistry of aquatic systems focusing on elements C, N, P, S, Fe and Mn. I am interested in understanding how aquatic biogeochemical cycles response to changing environmental conditions. I investigate the dynamics/variability of elemental fluxes and reaction rates, trace sources and transformations of elements, and study the interactions between geochemistry and biological activities. I use multiple approaches including field surveys, chemical analyses, laboratory experiments, stable isotopes, and diagenetic modeling.
My study sites include the Laurentian Great Lakes (Lakes Superior, Michigan, Huron, and Ontario), tropical Lake Malawi (East African), Lake of the woods (USA/Canada), the Chesapeake Bay, and Cape Cod Aquifer.
Directions and projects
Invasive mussels impacting sediment geochemistry in Lakes Michigan and Huron:
Recent invasion of the Laurentian Great Lakes by dreissenid mussels (zebra mussels and quagga mussels) has caused dramatic changes in the ecology and water chemistry of the lakes. The impacts of mussels on sediments have been hypothesized to play a key role, but the mechanisms remain unclear. We survey the lake floor of upper Great Lakes (Lakes Superior, Michigan, and Huron) on coverage of invasive mussels, characterize the sediment geochemistry, conduct benthic fluxes experiments to understand the impacts of mussels on biogeochemical transformations and exchanges of elements at the sediment-water interface. Using the results from sediment geochemistry and mussel physiology, we develop a whole-system mass-balance model to investigate the mussels' impact on nutrient dynamics in the water column.
This is an ongoing project collaborated by a group of geochemists and biologists at the Large Lakes Observatory (LLO). Learn more about our recent cruise on Lakes Superior, Michigan and Huron!
Polyphosphate (polyP) metabolism and dynamics in aquatic systems:
PolyP is a long-chain polymer of 3 to hundreds of orthophosphate (PO4) units linked by high energy bounds. It has been found in cells of many living organisms including aquatic primary producers (algae and cyanobacteria), considered to an important intracellular P reserve to survive low nutrient conditions. However its metabolism responding to nutrient levels and roles in P cycling in aquatic systems remain largely unknown. My work in polyP includes 1) Lab-controlled experiments on polyP metabolism in cyanobacteria responding to nutrient levels; 2) polyP in plankton in the eutrophic waters of coastal Lake Ontario responding to seasonal nutrient dynamics, and 3) the roles of polyP in P cycling in the upper Great Lakes (Lakes Superior, Michigan, and Huron).
Read more about our findings!
Manuscripts submitted and in preparation: - Li, J. and M. Dittrich. 2019. Dynamic polyphosphate metabolism in cyanobacteria responding to phosphorus availability. Environmental Microbiology (Accepted; PDF). - Li, J., A. Zastepa, S. Watson, and M. Dittrich. Polyphosphate in picoplankton responses strongly to phosphorus excess and deficiency in the dynamic coastal Lake Ontario (In preparation).
Phosphorus sources and turnover in the Chesapeake Bay:
Phosphorus is one of the limiting nutrients in the Chesapeake Bay, one of the most eutrophic systems in the world that suffered from algal blooms and summer hypoxia. Understanding P availability and its control on eutrophication is complicated by the multiple P sources and the dynamic P forms transformed by biogeochemical reactions. We characterized the form of particulate P in the water column using chemical extractions and 1D and 2D Nuclear Magnetic Resonance (NMR), traced the P sources, transformations, biological turnover using phosphate oxygen isotope ratios.
Publications: - Li, J., P. Reardon, J. P. McKinley, Y. Bai, S. Joshi, K. Bear, and D. P. Jaisi. 2017. Water column particulate matter a key contributor to phosphorus regeneration in coastal eutrophic environments, the Chesapeake Bay. Journal of Geophysical Research – Biogeosciences. 122: 737- 752 (Link)- Li, J., Y. Bai, K. Bear, S. Joshi, and D. P. Jaisi. 2017. Phosphorus availability and turnover in the Chesapeake Bay: Insights from nutrient stoichiometry and phosphate oxygen isotope ratios. Journal of Geophysical Research – Biogeosciences. 122: 811- 824 (Link)
Sediment diagenesis, geochemical cycles and budgets in Lake Superior:
This is part of my PhD Thesis project characterizing the sediment geochemistry of Lake Superior, the world's largest freshwater lake by area, and one of the most oligotrophic freshwater lakes! The work covered 13 locations in the lake with multi-year, multi-season field surveys, quantified diagenetic rates and fluxes (of C, N, P, Fe, and S), and investigate their temporal and spatial heterogeneity.
This work has generated multiple exciting findings including 1) Deep oxygen penetration and strong oxygen dynamics in carbon-poor sediments responding to bottom oxygen levels and carbon fluxes, 2) shifting directions of nitrogen fluxes (from flux into sediments nearshore to effluxes offshore) and low denitrification rates explain the accumulation of nitrate in Lake Superior, 3) Anammox (anaerobic ammonium oxidation) contributes significantly to nitrogen loss in the lake, 4) organic sulfur supports sulfate reduction in low-sulfate environments, important implications for ancient oceans, and 5) phosphorus fluxes in deeply oxygenated sediments controlled by organic matter mineralization.
Read more our findings in this largest freshwater lake in the world!
Publications: - Li, J., Y. Zhang, and S. Katsev. 2018. Phosphorous recycling in deeply oxygenated sediments in Lake Superior controlled by organic matter mineralization. Limnology and Oceanography. 63: 1372- 1385 (link)- Fakhraee, M., J. Li and S. Katsev. 2017. Significant role of organic sulfur in supporting sedimentary sulfate reduction in low-sulfate environments. Geochimica et Cosmochimica Acta. 213: 502-516 (link)- Crowe, S. A., A. H. Treusch, M. Forth, J. Li, C. Magen, D. E. Canfield, B. Thamdrup, S. Katsev. 2017. Novel anammox bacteria and nitrogen loss from Lake Superior. Scientific Reports. 7: 13757 (PDF)- Li, J., and S. Katsev. 2014. Nitrogen cycling in deeply oxygenated sediments: Results in Lake Superior and implication to marine sediments. Limnol. Oceanogr. 59 (2): 465–481 (link)- Li, J. S. A. Crowe, D. Miklesh, M. Kistner, D. E. Canfield, and S. Katsev. 2012. Carbon mineralization and oxygen dynamics in sediments with deep oxygen penetration, Lake Superior. Limnol. Oceanogr. 57:1634-1650 (link)
This is part of my PhD Thesis project characterizing the sediment geochemistry of Lake Malawi, one of the East African Great Lakes. The merometic tropical Lake Malawi is permanently stratified and remain anoxic below 200 meters, with its biogeochemical functioning differs substantially from temperate lakes. The work characterized the carbon, nitrogen, and phosphorus cycling in the water column and sediments and compiling whole-lake geochemical budgets.
Publications: - Li, J., E. T. Brown, S. A. Crowe, and S. Katsev. 2018. Sediment geochemistry and contributions to carbon and nutrient cycling in a deep meromictic tropical lake: Lake Malawi (East Africa). Journal of Great Lakes Research: https://doi.org/10.1016/j.jglr.2017.12.001 (link)- Katsev S., Verburg P., Lliros M., Minor E., Kruger B., and Li J.. 2017. Tropical meromictic lakes: Specifics of meromixis and case studies of Lakes Tanganyika, Malawi, and Matano. In Ecology of Meromictic Lakes, edited by R. Gulati, A. Degermendzhy, and E. Zadereev. Springer. (PDF)
Internal phosphorus loading in Lake of the Woods:
This is a project leaded by Master student Blandine Barthod, co-advised by Jiying and Dr. Maria Dittrich. In this work we characterize the sediment geochemistry in Lake of the Woods and quantify the internal loading of phosphorus from the sediment into the water column.
Let's look forward to Blandine's thesis and papers!
Tracing the sources and cycling of P in Cape Cod Aquifer:
Groundwater is the major source of freshwater in Cape Cod. A wastewater treatment plant built in the 1920s had stopped discharging into the infiltration beds since the 1990s. However, monitor work shows that a contaminant plume remains active, with high concentrations of C. N, and P even after 30 years. Using phosphate oxygen isotopes, we identified the sources of P to be reductive dissolution of Fe-P.
Read more about this work.
Manuscript in preparation:
- Li, J., S. Joshi, K. Bear, Y. Bai, D. LeBlanc and Deb Jaisi. The sources of the persistent ground-water phosphorus plume in the Cape Cod aquifer: a phosphate oxygen isotope study (In preparation).