Projects
Paleoceanography of Deep-sea Corals
Some corals live for hundreds to thousands of years and preserve biogeochemical information in seasonal growth rings. Compound-specific isotope analysis of individual amino acids in the proteinaceous skeletons of corals can be used to reveal shifts in plankton community structure over time. Primary production in surface waters exports nutrients to the deep ocean, in a process termed the biological pump.
For further reading: PNAS Sherwood 2010, Nature Sherwood 2013, Science McMahon 2015
Paleoceanography in the Gulf of Maine and Scotian Shelf
Marine sediment cores provide a long-term poxy for paleoceanographic changes on millennial timescales and preserve biogeochemical information in organic matter. We will use amino acid specific analysis of stable carbon and nitrogen isotopes (δ13CAA & δ15NAA) to disentangle changes in water mass influx in the Gulf of Maine and Scotian Shelf over geological timescales. This region is located at the boundary of two fundamentally different ecosystems (the nutrient-rich Gulf Stream and nutrient-poor Labrador Current derived waters) and, thus, highly sensitive to North Atlantic basin-scale climate forcing. This novel set of proxies can overcome the limitations of bulk isotope analysis and disentangle not only C and N sources but also constrain biogeochemical processes way beyond observational records.
Arctic Sea Ice Algae Fingerprinting
Stable carbon isotopes of amino acidss (δ13C-AA) reflect primary producer phylogenetic origins of fixed carbon. However, existing δ13C-AA data of marine primary producers are relatively scarce and mostly derived from laboratory cultures. This project is currently working on fingerprinting the δ13C-AA patterns of sea ice algae collected from the Arctic oceans to explore the potential to estimate their contribution to Arctic export production. Sea ice algae and phytoplankton are collected during summer expeditions to the Arctic on CCGS Amundsen. To our knowledge, this is the first study of amino acid isotope analysis of Arctic sea ice algae and phytoplankton.
Quantifying Sewage δ15N at Different Stages of Wastewater Treatment
This research project investigates the stable nitrogen isotope (δ15N) composition of sewage wastewaters. As one of the main contributors of point-source pollution to coastal marine environments, the harmful ecological effects of wastewater pollution are well known. Elevated δ15N compositions of marine organisms living downstream of wastewater treatment facilities is often used to identify sources of sewage contamination in aquatic environments (e.g. Costanzo et al. 2001; Lapointe et al. 2005). However, very few studies have actually quantified the δ15N of sewage wastewater directly, which leave discrepancies in the assessment of wastewater pollution. Therefore, the objective of this project is to measure the δ15N in dissolved and particulate forms of wastewater nitrogen at various stages of treatment, from raw sewage to tertiary treatment, in wastewater treatment plants operated by Halifax Water. In so doing, we will contribute to a better understanding of isotope fractionation associated with key steps during the transformation of sewage nitrogen.
Quantifying Impacts of Sample Preparation Techniques
Amino acids (AA) require derivatization in order to become volatile for gas chromatography, and cation exchange chromatography (CEC) and phosphate buffered saline (P-Buffer) are also regularly used to remove sample impurities prior to GC-IRMS. These techniques are common practice in sample preparation for compound-specific isotope analysis of AA (CSIA-AA), but their relative impact on CSIA-AA results is uncertain. This project applies three treatments (i. derivatization, ii. derivatization and CEC, iii. derivatization, CEC and P-Buffer) to AA standards and algae and sediment samples to assess the relative impacts on δ13C and δ15N chromatography, permille values, and reproducibility, as well as GC column ware.
Groundwater Methane in Nova Scotia (GaSP) and Colorado (AirWaterGas)
The Gas Seepage Project (GaSP) is a multi-phase collaborative research initiative aiming to mitigate methane emissions from the fossil fuel sector (oil, gas, coal) in the Canadian Maritimes. The project team includes Eastern Canadian academic and industry partners, and our particular contribution to the project has been to study groundwater methane. Read Kim's blog here.
We also mine the Colorado Oil & Gas Conservation Commission database of well water methane to study baseline data, contamination, and remediation, as part of the National Science Foundation Sustainability Research Network AirWaterGas Project.
Mobile Methane in the Denver-Julesburg and San Juan Basins (AirWaterGas)
We are currently working on a research paper in collaboration with NOAA, INSTAAR, and St. Francis Xavier University to isolate, attribute and measure methane emissions from various anthropogenic sources in Colorado's DJ Basin.
Developing Isoscapes of Antarctic Plankton
We are working with researchers at the Universidad de la República Uruguay to analyze compound-specific isotopes in samples of particulate organic matter collected in Antarctic waters. To our knowledge, the project is novel in that it is the first study of amino acid isotopes in southern ocean plankton.
