ABOUT OUR LAB
The development of our research group has benefited from the programs in geochemistry and hydrologic sciences at UMD to build a research program supported by NSF, NASA, EPA, Maryland Sea Grant, Chesapeake Bay Trust, and other funding sources. Our research focuses on the ecology and biogeochemistry of watersheds and aquatic ecosystems, primarily through long-term studies. Our research has focused on two overarching themes: (1) how do human interactions with land use, climate, and watershed geology transform the chemistry of inland waters (e.g., freshwater salinization, human-accelerated weathering, and eutrophication)? and (2) how can we evaluate and enhance watershed restoration strategies to reduce water pollution (e.g., storm and wastewater management)?
In our laboratory, water samples from long-term monitoring sites are filtered, preserved, and archived. The water is analyzed for biogenic elements such as carbon, nitrogen, sulfur, phosphorus, calcium, magnesium, potassium, silicon, iron, manganese, and others. Analysis of stable isotopes of carbon, nitrogen, and water provide important clues regarding identification of the sources, fluxes, and transformations of chemicals in natural environments through space and time. In the field, we measure in siturates of microbial and ecosystem process, and deploy and analyze sensor data for complementary measurements of oxygen availability, temperature, conductivity, and other water quality parameters.
In the future, we plan to build on current projects exploring the effects of the Freshwater Salinization Syndrome and human-accelerated weathering on the chemistry of inland waters, expanding our studies of the interactive effects of land use, climate, and geological change, and participating in long-term research networks and synthesizing data at regional and national scales through continued service in working groups and panels.
Freshwater Salinization Syndrome, Warming Rivers, and Human-Accelerated Weathering
Our research has shown that there have been long-term increasing trends in salinization, warming, and human-accelerated weathering and alkalinization of fresh water across North America (e.g., Kaushal et al. 2005, Kaushal et al. 2010, Kaushal et al. 2013, Kaushal et al. 2017, Kaushal et al. 2018). We coined the term "human-accelerated weathering" to describe how human activities have altered weathering rates and weathering products in rivers (Kaushal et al. 2013, Kaushal et al. 2017). We then coined the term "Freshwater Salinization Syndrome" to conceptualize the suite of synergistic effects that freshwater salinization has on multiple biogeochemical cycles and water quality (Kaushal et al. 2018). Elevated major ion concentrations have important consequences for drinking water quality, corrosion of infrastructure, contaminant mobilization, and regulating ecosystem processes. Our ongoing work on long-term changes in the chemistry of inland waters has been disseminated to the public in popular articles in outlets such as Science, Scientific American, the Atlantic, Nature Climate Change, US News and World Report, National Geographic, Natural History, The New York Times, Science News, and National Public Radio. These papers have also stimulated discussions regarding salt pollution, which is currently unregulated in many regions of the world.
The Urban Watershed Continuum, the Urban Karst, and Urban Evolution
We have made contributions to the nascent fields of urban ecosystem ecology, urban hydrology, and urban geochemistry through the development of conceptual models and empirical studies evaluating relationships between infrastructure and ecohydrological and geochemical processes. We developed "the urban watershed continuum" concept, and it is an ISI Web of Science highly cited paper (Kaushal and Belt 2012). Typically, watersheds are defined along topographic boundaries, and we showed that urban watersheds have much more dynamic boundaries across space and time due to the expanded role of infrastructure in the water cycle. We also expanded the definition of "urban karst" to include the widespread easily weathered impervious surfaces in urban watersheds, which can influence pH, buffering capacity, toxicity of metals, and water quality. Typically, geologic materials and geologic processes are underappreciated in many ecosystem studies, even though weathering plays an important role in regulating soil and water chemistry. We also developed the concept of urban evolution, where geological, biological, and chemical cycles evolve over time in the built environment based on adapting infrastructure and management decisions (Kaushal et al. 2014a, Kaushal et al. 2015). This collective work in urban ecology led to a special issue of Biogeochemistry, where I was the lead guest editor. In addition it led to speaking invitations and participations in working groups as part of the American Water Resources Association, American Geophysical Union, and W.M. Keck Foundation. It also led to an interview on National Public Radio's "Science Friday" https://www.sciencefriday.com/segments/understanding-the-urban-ecosystem/.
Land use and climate amplify watershed 'pulses' in chemical transport and transformation
Many streams and rivers now receive large loads of carbon and nutrients from human-dominated land use. Our work has shown that streams and rivers shift between chemical “transporters” that reflect anthropogenic changes in the landscape and atmospheric deposition, to chemical “transformers” that actively change the forms and ecological effects of elements delivered further downstream. We have shown that dynamic interactions between the natural and human components of the urbanizing landscape amplify storage and transport of various chemicals in watersheds including greenhouse gases (Kaushal et al. 2008, Kaushal et al. 2014b, Pennino et al. 2016, Smith et al. 2017). We are expanding global comparisons of nutrient transformations and the role of climate variability as a regulator in streams and rivers as part of a National Center for Ecological Analysis and Synthesis (NCEAS) working group. In addition, we are also now expanding to look at pulses of organic contaminants to drinking water supplies.
Evaluating Watershed Restoration Strategies
While nonpoint source pollution has increased over decades, the capacity of many suburban and urban streams to retain nutrients has been greatly impaired due to channel degradation from increased runoff, and decreased hydrological connectivity between streams and floodplain wetlands. We have been investigating stream restoration strategies to reduce river nutrient loads. Our contributions to the field of ecosystem restoration include empirical studies evaluating the effects of restoration on denitrification rates (Kaushal et al. 2008). We also conducted a global review of stream restoration studies (Newcomer Johnson et al. 2016), and a series of studies investigating the potential for coupling stormwater management and stream restoration approaches. We have also investigated the impacts of different geological substrates used in stream restoration on unintended consequences in water quality (Duan et al. 2018). I also worked with a group of other scientists and watershed managers supported by the U.S. Environmental Protection Agency to draft protocols for guiding stream restoration strategies to reduce nutrients in the Chesapeake Bay watershed, which have been previously missing. We also use stable isotope approaches to identify nonpoint source nitrogen pollution for prioritizing more effective nutrient reduction strategies in watersheds in the Western and Eastern U.S. (Kaushal et al. 2006, Kaushal et al. 2011, Pennino et al. 2016 a,b). We have been working with state agencies to use these approaches to prioritize and target pollution sources to drinking water supplies and coastal waters.