My lab’s research focuses on environmental geochemistry, specifically integrated organismal system responses to environmental change. Our current and future research interests can be linked by three strands. Each one is independent but dynamically connected to the others through the theme of environmental geochemistry.
Bioinorganic geochemistryThe first strand, bioinorganic geochemistry, is directly linked to integrated organismal system responses to environmental change. Our previous research in this area has centered on the environmental life history reconstructions of fish using otolith (ear stone) trace element chemistry. Otoliths are 98% aragonite; their chemistry records, at most times faithfully, the chemistry of the environment in which the fish lived. Since a new layer of material is deposited each day of their lives, it is possible to retrospectively sample the trace element chemistry of each layer using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). This record allows us to develop a life history of movement for individuals, and when pooled across stocks, for populations.
The aragonite is deposited on a web of protein, otolin-1. Based on our most research measurements of the metal chemistry of EDTA insoluble protein in otoliths from marine and freshwater fish, Otolin-1 appears to be a metalloprotein. Structural metalloproteins, as well as the inorganic deposition of calcium carbonate, occurs not only in fish otolith but in shellfish.
My most recent interests, and those of two of my PhD students (Bryanna Broadaway and Eric Freeburg), center on the impact of ocean acidification on biomineralization. By taking a first order look at the mineralogy and inorganic chemistry of the selected biominerals, we are looking to detect impacts on structure and function under conditions of increased pCO2 in ocean waters. We intend to extend these efforts to include not only structural changes but chemical and behavioral changes that, when examined together, allow us to better understand the impact of ocean acidification on communities. Additional research on other climate change impacts such as ocean freshening and temperature increase will also be completed. We seek collaborations for this work with biochemists and geneticists who can assist us in translating our results along the biological continuum to understand the impact of these environmental changes on the up and down regulation of genes and the impact on protein function.
Paleoenvironmental reconstructionA second strand of our research is paleoenvironmental reconstruction via isotopic and trace element chemistry of black shales. Black shales dominate over 30% of exposed sedimentary rock and are common at major mass extinction boundaries. We are working specifically on the Permo-Triassic boundary extinction and the reconstruction of paleoenvironments in marine boundary records. PhD students in my lab, such as Jeremy Williams, are integrating previous under-studied strata into the global chemostratigraphy. Through this work we seek to evaluate the role of ocean acidification, in combination with other environmental changes, in the deposition of these sequences and ultimately in the extinction event itself.
Other students are linking black shale related research to the effects of modern weathering of these metal-rich sediments on modern ocean chemistry. Weathering of these rocks has had a clear and demonstrable effect on global carbon cycles and oceanic isotopic composition (e.g., Os). Global environmental change alters, at variable temporal and spatial scales, chemical and mechanical weathering rates. These changes, combined with human-land surface interactions and anthropogenic inputs, impact global biogeochemical cycles. How these changes subtly impact the biogeochemical cycles of metals is, in many cases, poorly constrained by the gaps in our understanding of organometal fate and transport. The input of potentially toxic organometal species from black shale weathering could have profound impact on water and sediment quality and ultimately on ecosystem function. It is therefore vital that the linkages between black shales and organometal geochemistry be explored, and gaps in our understanding of the global cycling of these species be filled.
Interactions between groundwater and surface waterThe third strand of our research leverages trace element, isotopic and molecular tracers of water to evaluate the interactions between groundwater and surface water in geological and climatically dynamic environments.
Dr. Tom Darrah (post-doc) and students working with him are investigating the groundwater-surface water interactions on Nantucket Island where rapid recharge minimizes groundwater-rock interactions and enables groundwater discharge to the ocean with minimum fractionation of trace elements and isotopes. This work informs the role of groundwater discharge of coastal ocean chemistry. Dr. Darrah and students are also working on Lake Kivu in the Democratic Republic of Congo where the volcanic system of Nyiragongo and the high CO2 input into Lake Kivu present not only a unique laboratory to understand groundwater-surface water interactions but also to study the potential human health implications.
A PhD student, Alex Eisen-Cuadra, and colleagues in EEOS (Dr. Allen Gontz, Dr. Tom Darrah), Biology (Dr. Alan Christian), and Haiti (Dr. Emmanis Dorval) are exploring the interactions between the groundwater and Lac Azuie (EtangSaumatre), an evaporitic saline lake on the border of Haiti and the Dominican Republic. Combining helium/tritium isotope tracing, stable isotopes, trace elements, and SF6 Alex and the team are establishing the linkages between the groundwater and surface water in this region in order to answer basic science questions about the use of these tracers in dynamic settings, as well as to assist the local population in managing and sustaining its freshwater resources.
Dr. Cascade Sorte (post-doc) is working with a team of researchers from EEOS (Dr. Meng Zhou, Dr. Zong-Guo Xia, Dr. Mingshun Jiang, Dr. Robert Bowen) and Computer Science (Dr. Wei Ding) to develop a geospatial data network for the coastal watersheds of Massachusetts Bay that integrates human, geological, and ecological data and provides platforms for modeling transport and ecological – environment interactions.
Note to prospective students: The research done in our lab is analytically intensive; in addition all work has a field component. Graduate students and post-docs are expected to publish their research and to actively seek funding to support their work through applications to fellowships and the submission of grant proposals in collaboration with their advisor.
Undergraduates are also welcome! Please contact me about available research positions.