Current Research Projects:

Dr. Tony Rathburn

1) Collaborative Research: Calibration of a new approach to reconstruct ancient bottom water oxygen levels
(A.E. Rathburn, B. H. Corliss (Duke University), Co-PIs) Funded by NSF Marine Geology and Geophysics
We intend to use living (stained or labeled) specimens collected from a wide variety of habitats, including a 2011 transect across the oxygen minimum zone off San Diego, to examine the relationship between foraminiferal morphology and ambient dissolved oxygen. Together with graduate and undergraduate students and a research technician, we are using scanning electron imaging technology to compare pore characteristics of calcareous foraminiferal tests (shells) with dissolved oxygen contents of the water they are living in. The focus of this study is on epifauna (species that live on or above the sediment-water interface), but infaunal foraminiferal distribution and morphologies will also be examined, and compared with bottom water and pore water chemistry. To examine the relationships between test morphology and dissolved oxygen in a broad spectrum of environments, we will also evaluate the morphologies of epifauna from archived samples from around the world.

2) Pre-industrial sea-surface temperature reconstructions in the Tasman Sea.   A. E. Rathburn Co-PI with P. DeDeckker, (Australian National University, S. Schmidt (Université Bordeaux, France) and S. Schouten (Royal Netherlands Institute For Sea Research, The Netherlands).  Ship time funding by the Marine National Facility, Australia; ISU funding provided by the University Research Council.  Using samples collected along a transect on the Australian margin from Tasmania to Brisbane, we will examine microfauna collected in the water column and from seafloor sediments.  ISU students will examine the distribution, ecology and stable isotopic composition of benthic foraminifera from multicorer samples and compare results with those of environmental parameters and planktonic micro-organisms.

3.) Interdisciplinary approach to understand stable isotopic
disequilibrium in benthic foraminifera
(A.E. Rathburn, J. M. Bernhard
(Woods Hole Oceanographic Institution), and J. B. Martin (Univ. Florida)
Co-PIs) Funded by NSF Marine Geology and Geophysics
Using the remotely operated vehicle, JASON, we collected samples
from clam beds associated with seafloor methane seeps in Monterey Bay,
off the coast of California. Together with graduate and undergraduate
students and a postdoctoral researcher, we are using a variety of
recently developed techniques to understand why the isotopic
geochemistry of benthic foraminiferal carbonate is so very different
from that of the water they are living in. Foraminiferal chemistry and
distribution will be compared with foramininferal biology (food
vacuoles, symbionts, etc.), and pore water chemical and isotopic
composition. To examine a broad spectrum of isotopic environments, we
propose a coupled study of both non-seep sediments and nearby cold
methane seep environments, where steep geochemical gradients occur. The
specific hypotheses to be tested are:
A) The carbon isotopic composition of foraminiferal carbonate is
influenced by clustering of individuals within sub-millimeter seep
microenvironments.
B) The carbon isotopic composition of foraminiferal carbonate is
influenced by diet.
C) The carbon isotopic composition of benthic foraminiferal carbonate is
influenced by prokaryotic, non-photosynthetic symbionts.


4) Testing the impact of seasonality on benthic foraminifera as
paleoceanographic proxies.
(A. E. Rathburn, Co-PI with Scott Ishman
(Univ. of South. Illinois) and Jon Martin (Univ. of Florida)) Funded by
NSF Polar Programs
Together with graduate and undergraduate participants, we sampled
seafloor sites along a gradient of productivity (food availability) off
the Antarctic Penninsula in April (bloom time) and July(non-bloom time)
2008. By comparing the distribution and biogeochemistry of living and
dead foraminiferal assemblages with environmental characteristics
through time and space at these locations we will be able to discern
foraminiferal responses to seasonal and spatial changes in food
availability in this region. This information is critical to understand
how seafloor ecosystems will respond to future change, and to provide
modern analog data that can be used to assess environmental changes in
the past based on foraminiferal fossil assemblages.


5) Structure, function and evolution of authigenic, methane-derived
carbonate ecosystems
(A. E. Rathburn Co-PI with Lisa Levin and Greg
Rouse (Scripps Inst. Of Oceanography) and Victoria Orphan (California
Inst. of Technology)).  Funded by NSF Biological Oceanography.                                                 An interdisciplinary team including graduate and
undergraduate participants is studying newly recognized ecosystems
associated with carbonate rocks generated in seafloor methane seepage
environments. The site chosen are known locations of methane seep
habitats off Costa Rica and off Oregon (Hydrate Ridge). In a series of
cruises in 2009 and 2010, we will deploy experiments and recover samples
from seep and non-seep habitats in order to compare carbonate rock
ecosystems with those in nearby seep and non-seep environments.
Specifically, we are examining the ecology, biology and biogeochemistry
of foraminifera from these habitats.


6) Development of faunal and biogeochemical pollution proxies in the Venice Lagoon, Italy
(part of an interdisciplinary ScrippCo-PIs). Together with a team of Scripps Institution of Oceanography
scientists and Italian scientists (SIOSED Project), we examined
responses of organisms to contaminants and redistribution of seafloor
sediments in the Venice Lagoon, Italy. Specifically, we are studying
the ecological and trace metal biogeochemical responses of benthic
foraminifera over time and space within the Lagoon. By examining
recovery of foraminiferal assemblages on sediment banks artificially
created for the project, we are better able to understand the ecological
and geochemical consequences of sediment redistribution in the Lagoon.
One goal of this project is to develop microfaunal and biogeochemical
indicators of contaminants in order to monitor pollution impact and
recovery in this and other lagoons with a history of contamination.

 


Dr. Tony Rathburn

Interests
: Paleoceanography, Paleoecology, Micropaleontology, Geobiology and Biogeochemistry of methane seeps
                 
       

Selected Publications

Gieskes, J., Rathburn, A.E., Martin, J.B. Perez, M.E., Mahn, C., Bernhard, J.M., Day, S., (2011). Cold seeps in Monterey Bay, California: Geochemistry of pore waters and relationship to benthic foraminiferal calcite. Applied Geochemistry, 26: 738-746

Rathburn, A. E., L. A. Levin, M. Tryon, W. Ziebis, J. M. Gieskes, J. B. Martin, M. E. Pérez, F. J. Fodrie, C. Neira, G. Mendoza, P. A. McMillan, J. Adamic, J. Kluesner (2009) Geological and Biological Heterogeneity of the Aleutian Margin (1965-4822 m). Progress in Oceanography, 80 22-50.

Basak, C., Rathburn, A. E., Pérez, M.E. Martin, J. B., Kluesner, J. W., Levin, L.A., De Deckker, P., Gieskes, J.M., and Abriani, M. (2009) Carbon and oxygen isotope geochemistry of live (stained) benthic foraminifera from the Aleutian Margin and the southern Australian Margin. Marine Micropaleontology. 70 (2009) 89–101. doi:10.1016/j.marmicro.2008.11.002

Martin, J. B., Day, S. A., Rathburn, A. E., Perez, M. E., Mahn, C, Gieskes, J., 2004. Relationships between the stable isotopic signatures of living and fossil foraminifera in Monterey Bay, California. Geochemistry, Geophysics and Geosystems, 5, Q04004, doi:10.1029/2003GC000629.

Rathburn, A.E., Perez, M. E., Martin, J. B., Day, S. A., Gieskes, J., Mahn, C., Ziebis, W., Williams, D., Bahls, A. (2003) Relationships between the distribution and stable isotopic composition of living foraminifera and cold methane seep biogeochemistry in Monterey Bay, California. Geochemistry, Geophysics and Geosystems 4(12), 1106, doi:10.1029/2003GC000595.

Levin, L. A., Rathburn, A. E., Neira, C., Sellanes, J., Munoz, P., Gallardo, V., Salamanca, M., (2002) Benthic Processes on the Peru Margin: A transect across the oxygen minimum zone during the 1997-1998 El Ni?o, Progress in Oceanography 53: 1-27.

Rathburn, A. E., Perez, M. E., and Lange, C., 2001, Benthic-Pelagic Coupling in The Southern California Bight: Relationships Between Sinking Organic Material, Diatoms and Benthic Foraminifera: Marine Micropaleontology, v. 43, p. 261-271.

Rathburn, A. E., Levin, L. A., Held, Z. A., Lohmann, K. C., 2000, Benthic Foraminifera Associated with Cold Methane Seeps on the Northern Californian Margin: Ecology and Stable Isotopic Composition: Marine Micropaleontology, v. 38 p. 247-266.