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This project utilizes modern lakes in Maine to study organic depositional processes that are applicable to the study of lacustrine petroleum source rocks.  Specifically, the research is designed to quantify the sources of particulate organic matter in the water column, identify diagenetic alteration of the organic matter during deposition, and examine regionally coherent patterns of organic matter fluxes to the sediment surface over past millennia. 

Since May 2009, this project has involved four undergraduate students as paid research assistants, and an additional six undergraduate students who have volunteered, utilized samples for their senior theses, or worked on the project through federal work study funds.  Over two field seasons, we have spent eight weeks collecting sediment cores, geophysical sub-bottom data, and water column chemistry data, as well as deploying and retrieving sediment traps to study seasonal sedimentation cycles.  Five senior theses associated with the project are underway, one presentation has been given at a regional meeting, and two additional abstracts have been accepted for the 2010 Geological Society of America meeting.  Four students have had the opportunity to travel to the Environmental Protection Agency’s RI lab to work with Dr. Mark Cantwell and analyze the stable carbon and nitrogen ratios from their sediment samples. Students associated with the grant have all benefited greatly from the field and laboratory experiences that they have had, and two of these students are currently applying for graduate degree programs to start Fall 2011.

Over 70 meters of sediment core have been collected, and analyses of the sediment are under way.  The samples collected during the 2009-10 field seasons are sufficient to answer the research questions posed, and will provide the PI with material for future senior theses associated with organic matter deposition in Maine lakes at a number of time scales through the Holocene.  Additionally, new equipment purchased with grant funds, such as core storage reefers, a Stratabox acoustic sub-bottom profiler, sediment traps, and a sediment freeze corer, are instrumental for the professional growth of this new investigator.

At the present time, we have made significant progress on each of the three research questions posed:

1. Filtered water samples have enabled the quantification of the geochemical signature of particulate organic matter (POM) from modern lakes in Maine.  Stable carbon and carbon/nitrogen elemental data suggest that the POM in the study lakes is a composite of lacustrine algae and terrestrial C3 plants. Surface sediments from these same lakes have similar stable carbon ratios to the POM, but display enrichment in the C/N ratio. This observation is likely due to early diagenetic loss of nitrogen during the sedimentation process.  These results are from Dan Munroe’s (’11) senior thesis.
2. Sediment traps were deployed and recovered from three study lakes during the 2009-10 year.  These funnel-type sediment traps have amplified the sedimentation signal, enabling us to analyze each sample at < monthly resolution.  These samples have been processed, and carbon and nitrogen isotopic analyses are currently underway.  ML Crispo (’11) is investigating the sediment trap samples for her senior thesis.
3. Sediment core samples are being utilized to examine variability in organic matter origin and fluxes over the late Holocene.  Low frequency variability in organic matter deposition in Tea Pond and Conroy Lake (hundreds of kilometers apart) are coherent, suggesting regional influences on the production and preservation of organic matter in these meromictic lakes.  Ongoing work is utilizing the annually laminated sediments and additional radiocarbon dates to better constrain the age models, allowing for the examination of higher frequency coherency in the region.  In addition, sub-bottom geophysical data are permitting facies analysis in conjunction with the core studies to provide a more complete understanding of the lacustrine depositional processes.  Results and ongoing analyses are associated with Richard English’s (’11), Brad Hammond’s ('11), and Cam Morissette’s (’11) senior theses.