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USGS Scientists Examine Offshore Impacts of Hurricane Katrina

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Above: The research vessel Cape Hatteras off the Mississippi River mouth, October 2005. The Cape Hatteras is owned by the National Science Foundation. [larger version]

U.S. Geological Survey (USGS) scientists led a quick-response cruise aboard the research vessel Cape Hatteras in mid-October 2005 to study the impacts of Hurricane Katrina on the Louisiana shelf. Sponsored jointly by the National Science Foundation (NSF) and the USGS Coastal and Marine Geology Program and Earth Surface Dynamics Program, the cruise collected data in the lower Mississippi River and on the northern continental shelf off Louisiana to investigate potential downriver environmental impacts and to assess storm-related sediment transport on the shelf.

Hurricane Katrina caused major damage to natural-gas and petroleum facilities in the Gulf of Mexico, leading to oil spills whose exact extent has not yet been determined (see preliminary interpretations of satellite imagery by Russell Rykhus in Eos, v. 86, no. 41, p. 381-382). The storm's energy also disrupted oxygen-depleted waters in the previously stratified water column of the northern Louisiana shelf and thus abruptly ended the occurrence of widespread hypoxic conditions observed in this region during summertime. (Visit URL http://www.lumcon.edu/Information/news/, select year 2005, then click "Mapping of Dead Zone Completed" to learn more about this oxygen depletion.) A highly productive fisheries industry may be at risk from storm-related pollution and catastrophic sediment transport.

Among those studying these potential environmental threats are USGS scientists Peter Swarzenski, Lisa Osterman, Chris Reich, John Ricardo, and Dick Poore (St. Petersburg, Fla.) and their academic collaborators David Senn, Michael Bank, and Laurel Schaider of the Harvard School of Public Health; Rob Mason and Terill Hollweg of the University of Connecticut; Alan Shiller, Lyndsie Gross, and Jinggong Dong of the University of Southern Mississippi; David Hollander, Jen Flannery, Marianne Dietz, Zhiqiang Chen, Chuanmin Hu, and Frank Muller-Karger of the University of South Florida; and Nancy Rabalais of the Louisiana Universities Marine Consortium (LUMCON).

The October cruise had the following broad objectives:

  • To assess posthurricane offshore sediment-transport processes, with the help of data from a prehurricane (May 2005) cruise on the research vessel Pelican that established the recent geochronologic framework at selected sites on the Louisiana shelf by using the radioactive isotopes 7Be, 210Pb, and 137Cs to date sediment
  • To examine the biogeochemical signatures of a suite of trace elements in Mississippi River water across a salinity gradient-from low-salinity (~1) water at a site about 40 km upriver from the mouth of the Mississippi to higher-salinity (36) water in the Gulf of Mexico about 150 km southwest of the river mouth.
  • To analyze organic and inorganic contaminants in sediment immediately adjacent to the river mouth to determine whether their sources can be identified—are they normally present in Mississippi River water, or were they introduced by pumping of floodwaters into the river?
  • To continue research on historical oxygen-depletion (hypoxia) events and storm-induced benthic-ecosystem changes, using benthic-foraminiferal assemblages
  • To further study the cycling of mercury and methylmercury in the pore waters and water column in areas of recurring hypoxia

To achieve these objectives, the scientific staff sampled the water column and bottom sediment at previously established and new sites across the Louisiana shelf, using various sampling and coring devices. Planned onshore studies of cores collected on this cruise will include analyses of a suite of organic compounds and inorganic trace elements, mercury and methylmercury, 7Be, 210Pb, 137Cs, foraminiferal assemblages, and grain size.

The research vessel Cape Hatteras departed from Cocodrie, La., on October 14, 2005, carrying 12 cruise participants. We owe special thanks to Don Rice of NSF, who funded this quick-response cruise; John Haines (USGS Coastal and Marine Geology Program Coordinator) and Tom Armstrong (USGS Eastern Region Science Coordinator), who have jointly supported USGS efforts; and the captain and crew of the Cape Hatteras, who provided superb and invaluable help with all things shipboard. Joseph Ustach (Duke University) kindly coordinated the ship's schedule around a multitude of hurricanes. The generosity of Steve Rabalais (LUMCON) in loaning us a large box corer from the research vessel Pelican ensured successful sediment collection.

Related Web Sites
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in this issue: Fieldwork
cover story:
USGS Scientists Investigate New Orleans Levees

special feature:
Post-Katrina Cleanup—a Volunteer's Reflections

Offshore Impacts of Hurricane Katrina

Sediment-Toxicity Studies in Western Long Island Sound

Sea-Floor Geology Off Massachusetts Coast

Alvin Dives to Deep-Water Coral Habitats

Research Study Links Urbanization to Amphibian Decline

Outreach San Francisco Bay Floor Explored

Briefing on Coastal Research in Hawai'i

USGS Research on the Kona Coast, Hawai'i

Meetings Third International Symposium on Deep-Sea Corals

Awards Award for USGS Map Hawaii's Volcanoes Revealed

Staff USGS Citizen Soldier on the Move!

Native-Plant Landscaping in Florida

Publications New Book on Benthic Habitats and the Effects of Fishing

Dec. 2005 / Jan. 2006 Publications List

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