David B. Field, Ph.D.
Visiting Assistant Professor of Marine SciencesOffice:
Phone: (808) 356-5231
Courses:BIOL 3081 Ecology Laboratory
MARS 6002 Marine Systems II (Chemical Oceanography)
MARS 6110 Graduate student seminar
MARS 6210 Graduate student seminar
Education:Ph.D. Scripps Institution of Oceanography (UCSD): Oceanography, 2004
B.S. University of California, San Diego: Biology (Ecology, Behavior, and Evolution), Minor: Spanish Literature, 1995
OAP Universidad Arturo Prat, Iquique, Chile; (Opportunities Abroad Program) 1994
Global change, decadal-to millennial-scale variability, paleoceanography, geobiology, sedimentary processes, geochemical tracers, fisheries oceanography, plankton ecology
An overarching interest is to understand natural variability in ocean climate and marine ecosystems and distinguish natural variability from anthropogenic effects on ocean systems. Such work is done by linking knowledge of ocean processes observed in modern records with historical observations and geological archives, and thus spans both ecological and geological timescales and processes. I have largely worked with fossils within marine sedimentary records but aim to work with fossil and living corals.
Much of my investigations of past climate changes have been done with sediment cores from laminated sediments. Sediments accumulating in extremely low oxygen environments, such as the Santa Barbara Basin, are not exposed to benthic organisms that usually mix and bioturbate ocean sediments. Thus sediment from disoxic environments preserve seasonal or annual differences in sediment type, which provides very high-resolution records within the sediments. Fossil plankton within the sediments, such as foraminifera, diatoms, coccolithophorids, etc., as well as their isotopic signatures reveal changes in water temperature and ocean climate. There are many other geochemical approaches to inferring past changes as well.
In order to interpret these records from marine sediments I have also examined how environmental factors affect the abundance and distribution of living foramininfera by taking plankton tows across the California Current.
Another fossil found within ocean sediments are fish remains, scales, bones, and otoliths, of very abundant pelagic fishes like sardines and anchovies. By quantifying the changes in abundance of fish scales in different layers of ocean sediments, we can infer past changes in population sizes prior to the onset of industrial fishing. We also fish scale records with other paleo records, historical records of fish catch, guano harvest, or archived shipboard measurements of Sea surface temperature and/or wind speed to understand how pelagic fish populations respond to environmental changes over long timescales.
Another tool for inferring some of the potential mechanisms responsible for variability in fish populations is to examine their isotopic signatures of δ15N and δ13C. I have measured δ15N and δ13C on tissues of living sardines in the California Current as well as making measurements from sardines raised in laboratory setting of controlled temperatures and on different diets to understand how isotopic signatures are acquired in scales and muscle tissue. Such information is useful for understanding population variability and trophic dynamics. Another potential goal is to use δ15N and δ13C of fish scales preserved in sedimentary records to test for long-term relationships between nutrient input and trophic level on relative changes in the population sizes of sardines and anchovies, as inferred from fish scale deposition rates.
I am interested in starting research in Hawai’i in the areas of 1) history of Hawaiian fish ponds (by taking sediment cores in the ponds), 2) reconstructing past changes in ocean climate from isotopes and trace elements found in fossil coral skeletons, 3) examining changes in runoff and nutrients with trace elements that have been incorporated into living and fossil coral skeletons.
An interesting link: http://www.mbari.org/news/news_releases/2006/forams.html