Tessa M. Hill, Ph.D.

Students

Ongoing Research

Bamboo corals as records of climate change in the ocean's interior

Left: Pieces of a bamboo coral skeleton, showing calcite sections with organic nodes. Scale bar is 5cm.

This research utilizes bamboo corals, which reside at intermediate depths (250 to 2500m) along the California margin as records of the temperature, geochemistry, and ventilation history of north Pacific intermediate waters. This research project is in collaboration with H. Spero (UC Davis) and investigators at the Monterey Bay Aquarium Research Institute (MBARI).
Above: Cross-sectional view of calcite skeleton of bamboo coral, showing radial growth bands.

Bamboo corals have a skeleton that is composed of both calcite sections and organic nodes. Bamboo corals produce visible alternating bands in their calcium carbonate skeleton.  The frequency of the banding is hypothesized to be annual or sub-annual (Roark et al., 2005).  Bamboo corals can live for hundred of years, preserving a high-resolution record of environmental conditions at intermediate depths. Despite the geographic extent and importance of these corals as part of the deep-sea ecosystem, very little is understood about their biology, geochemistry, and biogeography.

For more information, please visit the website of our recent MBARI/NOAA cruise, and check out our recently submitted abstract to the American Geophysical Union Fall 2007 Meeting, Link to PDF >>

This project is supported by the National Science Foundation and NOAA’s Undersea Research Program

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Past and present pH variability in Coastal California: Impacts of anthropogenic ocean acidification


Bodega Ocean Acidification Research: Experimental setup for culturing organisms in controlled CO2 and pH environments. Pictured: Dr. Eric Sanford, Annaliese Hettinger (Ph.D student) and Jennifer Hoey (REU student)
Climate change impacts due to the release of anthropogenic carbon dioxide (CO2), including ocean and climate warming and changes in the hydrological cycle, have received intense international attention from scientists and policy-makers for several decades (IPCC, 2007 and references therein). As anthropogenic CO2 is added to the atmosphere, a portion of the CO2 is absorbed by the ocean, and this process leads to a decline in ocean pH.  However, the potential consequences of ocean acidification have only recently received increased attention (Caldeira and Wickett, 2003; Feely et al., 2005; Orr, et al., 2005), despite predictions that reductions in ocean pH are likely to accelerate in the future. Improving our understanding the impact of changes in ocean pH on the carbonate saturation state of seawater and on marine organisms and ecosystems is increasingly urgent as many of them form shells or internal skeletons made of calcium carbonate.

Our interdisciplinary research group (Gaylord, Sanford, Hill and Russell) aims to investigate the impacts of ocean acidification on coastal California environments. A fundamental question in understanding the response of organisms to shifts in pH includes investigating both natural and anthropogenic variability in the pH and carbonate system.  To that end, our research project includes:

  • Culturing of key species in the laboratory under reduced pH conditions
  • Monitoring modern pH variability on the Northern California coast using pH sensors and oceanographic transects
  • Reconstructing past pH variability utilizing geochemical proxies for pH in marine carbonates

Causes and consequences of the Storegga submarine landslide: Was methane hydrate involved?

Location of Storegga slide

The Storegga slide (offshore Norway) is the largest known submarine slide on a continental margin, affecting an area of ~95,000 km 2 and associated with tsunami deposits in Scotland, Norway, and Iceland (Haflidason et al., 2005; Bondevik et al., 2005). The Storegga landslide occurred in the early Holocene (~8.1 ka) and is hypothesized to be associated with the disturbance of gas hydrates on the Norwegian continental margin during deglacial warming and sea level rise. I am investigating the sedimentary history of the Storegga landslide and associated implications for gas hydrate stability, with collaborators C. Paull (MBARI), B. Ussler (MBARI) and S. Holbrook (U Wyoming).

Analyses of benthic foraminiferal assemblages from the Storegga slide, on board the R/V Knorr, September 2004.

 

For more information on this project, please check out our recently submitted abstract to the American Geophysical Union Fall 2007 meeting, Link to PDF >>

 

 

 

 

 

 

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