Research Projects

Marine productivity and the carbon cycle

Past hydrological changes recorded in stalagmites

Marine productivity and the carbon cycle

I have worked on developing new indicators for productivity variations from the chemistry of calcite coccoliths produced by marine coccolithophorid algae. I have used laboratory cultures and sediment trap time series for verification, and applied these indicators to study past productivity variations in the Quaternary Arabian Sea and Bay of Bengal and over the Paleocene-Eocene Thermal Maximum. As part of this work, we developed a new method for picking individual coccoliths with a micromanipulator, and mounting them for trace element analysis via ion probe (SIMS) in collaboration with Nobu Shimizu at Woods Hole Oceanographic Institute. Funding sources U.S. NSF and Petroleum Research Fund.

Algal evolution

If current trends continue, over the next few centuries atmospheric CO₂ from will likely to reach levels last seen tens of millions of years ago. Evidence suggests that modern calcifying algae and diatoms employ a range of carbon acquisition strategies (such as active carbon concentrating mechanisms) according to their cell geometry and the pH and carbon speciation of the seawater in which they live. However, we have observed that calcifying algae from 60 million years ago apparently had a single or less diverse array of carbon acquisition strategies. The project will identify and calibrate novel geochemical fossil indicators for adaptation and evolution in carbon acquisition strategies in eukaryotic algae, and apply these indicators to establish the magnitude, rate, and timing of changes in carbon acquisition strategies by algae in response to past changes in the carbon cycle and atmospheric CO₂ over the past 60 million years. Funding source is ERC- EC VII Plan Marco. Positions are available in this project.

Past Hydrological Changes Recorded in Stalagmites

We are working to reconstruct past changes in hydrological balance (P-E) and precipitation dynamics (moisture source) in NW Spain, from orbital timescales to multidecadal variations over the last few millennia. This region is sensitive to NAO influence and potential orbital excitation of climate modes. We are also working to ascertain if the frequency of extreme precipitation events leading to floods can be reconstructed from stalagmites. Dripwater monitoring, with a device we designed, has been conducted in various caves since 2003 and synoptic scale rainwater isotope monitoring since 2006. This project is in collaboration with geomorphology group at Oviedo (Montse Jimenez, Maria Jose Dominguez), dating expertise at U. Minnesota (R. Larry Edwards, Hai Chang), and others (Ana Moreno, Steve Burns, Ricardo Trigo, Ana Mendez). Principal funding is from Spanish Ministry of Science and Asturias government regional science ministry.

Experience and Awards

PhD, Princeton University, 1998

Gretchen Bletchschmidt Award, GSA, 1996

NATO-NSF Postdoctoral Fellowship, 1998-2000

EGU Outstanding Young Scientist Award, 2006

DuPont Young Professor Award, 2008

ERC Starting Investigator Award, 2009

Teaching Experience:

Williams College: (tenure awarded): The Carbon Cycle, Climate Changes, Environmental Geology, Introduction to Environmental Science

Univ. of Oviedo: Masters courses in Climate Change, Marine Biogeochemical Cycles and Paleoceanography

Positions Available

Stable Isotope Instrument Specialist

Postdoctoral position in biogeochemistry of diatoms and coccolithophorids

Two additional postdoctoral/doctoral positions advertised soon

About Oviedo and the university

Stable Isotope Instrument Specialist

The Geology Department at the University of Oviedo, in Oviedo, Northwest Spain, invites applications for a position to run and maintain a new stable isotope laboratory. The position is an initial 2 year appointment, renewable for an additional 2-3 years. The primary project will be assessing precedents of algal adaptation to atmospheric CO2 levels in the geological record and will involve EA- and GC-IRMS determinations on organic phases and measurement of carbonates. The instrument specialist will participate actively with the research team in the scientific evolution of the project. The successful candidate will have a Masters or PhD in geology, oceanography, or related biological sciences, and several years experience running EA- and GC-IRMS applications. The candidate is expected to oversee modifications to the instrument required for adaptation for small sample sizes, conduct sample analyses, and maintain and troubleshoot the instrument. The position, available 1 December 2009, offers competitive salary, 1 month vacation, and free health care for the candidate and his/her family in the public health care system. The position is open to candidates of all nationalities; hire of a candidate from non-EU country may entail a 1-2 month delay in start date pending approval of work permit. To apply, please send a current CV and brief description of your experience and research interests to Heather Stoll (hstoll@geol.uniovi.es).

Postdoctoral Position in Biogeochemistry of marine algae

The Geology and Ecology Departments at the University of Oviedo, in Oviedo, Northwest Spain, invite applications for a Postdoctoral Associate to conduct research on carbon acquisition strategies of marine algae, as part of a larger EC-funded project assessing precedents of algal adaptation to atmospheric CO2 levels in the geological record. The position is a 3 year appointment. The research will be jointly conducted between the marine ecology unit in biological sciences and the geochemistry unit in the geological science department; these groups have a strong marine ecology program, including one of the longest monthly time series of phytoplankton and nutrient monitoring (in the Bay of Biscay), and strong expertise in low temperature geochemistry. A part time laboratory technician will be available to assist in culture maintenance.

The successful candidate must hold a PhD in oceanography or related biological sciences at the time of appointment, and have several years experience in the controlled laboratory culture of marine algae such as coccolithophorids or diatoms and characterization of their growth rates and metabolism. The position, available 1 December 2009, offers competitive salary, 1 month vacation, and free health care for the candidate and his/her family in the public health care system. The position is open to candidates of all nationalities; hire of a candidate from non-EU country may entail a 1-2 month delay in start date pending approval of work permit. To apply, please send a current CV and brief description of your experience and research interests to Heather Stoll (hstoll@geol.uniovi.es).

Two additional postdoctoral and/or doctoral positions

Two additional postdoctoral and/or doctoral positions in the Geology department will be advertised soon to, for candidates with experience and interest in Cenozoic calcareous nannofossil biogeography, Cenozoic diatom biogeography, stable isotope measurements in organic matter, or ion probe geochemical techniques.

About Oviedo, Spain

Oviedo is a small city of 200,000 with historic pedestrian only city center and classic cultural offerings (opera, orchestra). The location is ideal for those interested in active outdoor lifestyle, only 30 km from the coast (beaches, surfing) and 45 km from the Cantabrian mountains (hiking/backpacking, cycling, rockclimbing). More information is available on the University of Oviedo Webpage Guide for International Students.

Publications

Published

In review

Published

Stoll, H.M. and Shimizu, N. Micro-picking of nannofossils in preparation for analysis by secondary ion mass spectrometry. Nature Protocols, 2009.

Moreno, A., Valero-Garces, B., Jimenez-Sanchez, M., Dominguez, M.J., Mata, P., Navas, A., Gonzalez-Samperiz, P., Stoll, H., Farias, P., Morellon, M., Corella, J., Rico, M. The last deglaciation in the Picos de Europa National Park (Cantabrian Mountains, Northern Spain). Journal of Quaternary Science, 2009.

Langer, G., Nehrke, G., Thoms, S., Stoll, H. Ba partitioning in coccoliths of Emiliania huxleyi. Geochimica et Cosmochimica Acta, 2009.

Stoll, H.M., Shimizu, N., Ziveri, P., and Archer, D. Coccolithophore Productivity Response to Greenhouse Event of the Paleocene-Eocene Thermal Maximum, Earth and Planetary Science Letters,258, p. 192-206, 2007.

Stoll, H.M., Vance, D. and Arevalos, A.’05 Nd isotope records from Bay of Bengal constrain effect of Northern Hemisphere cooling on ITCZ movement. Earth and Planetary Science Letters 255, 213-228, 2007.

Stoll, H.M., Ziveri, P., Shimizu, N., Conte, M., and Theroux, S’05. Relationship between coccolith Sr/Ca ratios and coccolithophore production and export in the Arabian Sea and Sargasso Sea, Deep Sea Research II 54, p. 581-600. (Special Issue on Role of Marine Organic Carbon and Calcite Fluxes in Driving Global Climate Change, Past and Future), 2007.

Ziveri, P., DeBernardi, B., Baumann, K., Stoll, H.M., and Mortyn, P.G. Sinking of coccolith carbonate and potential contribution to organic carbon ballasting in the deep ocean. Deep Sea Research II 54, p. 659-675. (Special Issue on Role of Marine Organic Carbon and Calcite Fluxes in Driving Global Climate Change, Past and Future), 2007.

Stoll, H.M., Arevalos, A.’05, Burke,A.’06, Ziveri, P., Mortyn, P.G., Shimizu, N. and Unger,D. Seasonal Cycle of Coccolithophorid and Biogenic Carbonate Productivity in Bay of Bengal Sediment Traps. Deep Sea Research II 54, (Special Issue on Role of Marine Organic Carbon and Calcite Fluxes in Driving Global Climate Change, Past and Future), 2007.

Stoll, H.M., Shimizu, N., Arevalos, A.’05, MatellN.’06, Banasiak,A.’08, and Zeren, S. ‘05Insights on Coccolith Chemistry from a New Ion Probe Method for Analysis of Individually Picked Coccoliths. Geochemistry Geophysics Geosystems, 8, Q06020, doi:10.1029/2006GC001546, 2007. (como la biblioteca no recibe esta revista he incluido mi “proof” y la portada disponible en pagina web de la revista)

Stoll, H.M. Climate Change: The Arctic tells its story (News and Views). Nature, 441, 579-581.

Stoll, H.M. Limited range of interspecific vital effects in coccolith stable isotopic records during the Paleocene-Eocene Thermal Maximum. Paleoceanography, doi 10/1029PA2004001046, 2005

Stoll, H.M. Response to comment on “Coccolith Sr/Ca records of productivity during the Paleocene-Eocene Thermal Maximum from the Weddell Sea”. Paleoceanography, v.19 doi 10.1029/2003PA000971, 2004.

Stoll, H.M. and Bains, S.Coccolith Sr/Ca records of productivity during the Paleocene-Eocene Thermal Maximum from the Weddell Sea Paleoceanography, v. 18 doi 10.1029/2002PA000875, 2003.

Ziveri, P*., Stoll, H.M*., Probert I. , Klaas, C., Geisen, M., Young J., and Ganssen, G. Stable Isotope Vital Effects in Coccolith Calcite. Earth and Planetary Science Letters 210, p. 137-149, 2003. (authors marked with asterisk contributed equally to this work as noted in the article)

Stoll, H.M., Ziveri, P., Geisen, M., Probert, I., and Young, J.R. Potential and limitations of Sr/Ca ratios in coccolith carbonate: new perspectives from cultures and monospecific samples from sediments. Phil. Trans. Roy. Soc. of Lond. A 360, 719-747, 2002.

Stoll, H.M., Rosenthal, Y., and Falkowski, P. "Climate proxies from Sr/Ca of coccolith calcite: calibrations from continuous culture of Emiliania huxleyi." Geochimica et Cosmochimica Acta, 66, 927-936, 2002.

Stoll, H.M. and Ziveri, P. Separation of mono-specific and restricted coccolith assemblages from sediments using differential settling velocity Marine Micropaleontology, 46, 209-221, 2002.

Stoll, H.M, Ruiz-Encinar, J., Garcia-Alonso, J.I., Rosenthal, Y., Klaas, C., and Probert, I. A first look at paleotemperature prospects from Mg in coccolith carbonate: cleaning techniques and culture measurements. Geochemistry, Geophysics, Geosystems, 2001.

Stoll, H.M, Klaas, C., Probert, I. P.,Ruiz-Encinar, J., Garcia-Alonso, J.I.Calcification rate and temperature effects on Sr partitioning in coccoliths of multiple species of coccolithophorids in culture. Global and Planetary Change 34, 153-171, 2002.

Stoll, H.M. and Schrag, D.P. Sr/Ca variations in Cretaceous carbonates: relation to productivity and sea level changes. Palaeogeography, Palaeoclimatology, Palaeoecology 168, 311-336, 2001.

Stoll, H. M., and D.P. Schrag, Coccolith Sr/Ca as a new indicator of coccolithophorid calcification and growth rate. Geochemistry Geophysics Geosystems, 1, 1-24, 2000.

Stoll, H. M. and D. P. Schrag. High resolution stable isotope records from the Upper Cretaceous of Italy and Spain: Glacial episodes in a greenhouse planet? GSA Bulletin, 112, 308-319, 2000.

Stoll, H. M., D. P. Schrag, and S. C. Clemens, Are seawater Sr/Ca variations preserved in Quaternary foraminifera? Geochimica et Cosmochimica Acta, 63, 3535-3547, 1999.

Stoll, H. M. and D. P. Schrag, Effect of Quaternary sea level cycles on the Sr budget of the ocean. Geochimica et Cosmochimica Acta, 62, 1107-1118, 1998.

Karabinos, P., S.D. Samson, J.C. Hepburn, and H. M. Stoll. Taconian orogeny in the New England Appalachians: Collision between Laurentia and the Shelburne Falls Arc. Geology, 26, 215-218, 1998.

Stoll, H. M. and D. P. Schrag, Evidence for Glacial Control of Rapid Sea Level Changes in the Early Cretaceous. Science, 272, 1771-1774, 1996.

In review

Graduate students in italics

Gibbs, S., Stoll, H.M., Bown, P., and Bralower, T. Ocean acidification and surface water carbonate production across the Paleocene-Eocene Thermal Maximum. Paleoceanography, in review.

Auliaherliaty, L. Stoll, H.M., Ziveri, P. Coccolith Sr/Ca ratios in Eastern Mediterranean: production vs. export processes. Marine Micropaleontology, in review.

Moreno, A., Stoll, H., Jimenez-Sanchez, M., Cacho, I., Valero-Garces, B., Ito, E., and Edwards, R.L. A speleothem record of glacial rapid climatic changes from Northern Iberian Peninsula, Global and Planetary Change, in review.

Dedert, M., Stoll, H.M., Ziveri, P. Productivity response of calcareous nannofossil response to early Eocene Thermal event (EMT2) Elmo at Site 1265A, Walvis Ridge. Earth and Planetary Science Letters, in review.