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A Research Cruise to Investigate Natural Versus Human Impacts on Marine Ecosystems in Hood Canal, Washington

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In September 2013, researchers from the U.S. Geological Survey (USGS) and the University of Washington (UW) collaborated on fieldwork in Hood Canal, a long, narrow fjord in Puget Sound, Washington. The bottom waters in parts of Hood Canal and its terminus, Lynch Cove, suffer periodic depletions in dissolved oxygen (hypoxia), which can negatively affect ecosystem health. Most fish, for example, cannot live in hypoxic water (water with less than 30 percent of the dissolved oxygen it could contain at the prevailing temperature and pressure). Oxygen depletion in the water column most commonly results from the introduction of nutrients—such as nitrogen and phosphorus—that spur the growth of algae, whose eventual decomposition by bacteria consumes oxygen. Natural nutrient sources that contribute to low bottom-water oxygen in Hood Canal—such as land-derived plant residues and animal waste—are likely enhanced by decades of widespread urbanization, agriculture, and forestry. The recent research is directed at distinguishing natural from anthropogenic controls on bottom-water oxygen depletion and other ecosystem stressors.

Location map showing coring stations
Above: Hood Canal, Washington, showing locations of kasten coring stations. [larger version]

USGS personnel from the Pacific Coastal and Marine Science Center (PCMSC, Santa Cruz, California) and the St. Petersburg Coastal and Marine Science Center (SPCMSC; St. Petersburg, Florida) worked with colleagues from UW aboard the research vessel (R/V) Centennial to collect sediment samples for their study.

Loading the research vessel
Above:Loading the research vessel (R/V) Centennial at its home port, Friday Harbor Laboratories, University of Washington, on San Juan Island, Washington. [larger version]

Under the direction of chief scientists Peter Swarzenski (USGS, PCMSC) and Andrea Ogston (School of Oceanography, UW), the R/V Centennial steamed to Hood Canal from Friday Harbor, Washington. After the vessel entered the study area, Emily Eidam (School of Oceanography, UW) and Cordell Johnson (USGS, PCMSC) assisted in collecting a series of Van Veen surface-sediment grab samples and a long kasten core.

Deploying a 3-meter (10 foot) kasten corer off the R/V Centennial.
A 2-plus meter (6-plus foot) kasten core of mud retrieved from Hood Canal.
Above: Deploying a 3-meter (10 foot) kasten corer off the R/V Centennial. [larger version]
Below: A 2-plus meter (6-plus foot) kasten core of mud retrieved from Hood Canal. [larger version]

The Van Veen grab sampler has a clam-shell-type scoop that collects bottom sediment with minimal disturbance to the sediment surface (see examples of grab samplers). The kasten corer has a rectangular-shaped barrel with a heavy weight at the top that helps push it into the sediment (see photographs above).

Sediment sampling continued at multiple sites seaward of the Skokomish River delta and into Lynch Cove. Coring sites were selected to aid in the interpretation of ecosystem stressors as well as the identification of sediment sources and the deciphering of delta evolution. Elizabeth Nesbitt and Ruth Martin (both from the Burke Museum of Natural History and the Earth and Space Sciences Department, UW) took subsamples from the cores to investigate benthic infauna—animals living in the sediment—including foraminifera, single-celled organisms whose shells commonly record environmental conditions at the time of their growth. Mary McGann (USGS, PCMSC) and Lisa Osterman (USGS, SPCMSC) will examine subsets of foraminifera for evidence of invasive species (McGann) and low-oxygen events (Osterman).

View toward the Olympic Mountains from the R/V Centennial in Hood Canal, Washington.
Above: View toward the Olympic Mountains from the R/V Centennial in Hood Canal, Washington. [larger version]

Ably assisted by the captain (David Duggins) and crew (Scott Lindgren) of the R/V Centennial, the scientific party kept five long kasten cores and more than a dozen Van Veen grab samples. The sediment will be analyzed first for short-lived radioisotopes (for example, 210Pb, 137Cs, 7Be) to establish a representative geochronology at each sampling site. Subsequently, a suite of analyses will include X-radiography; grain-size analysis; concentrations and isotopic compositions of carbon and nitrogen; concentrations of trace elements such as vanadium, rhenium, and uranium, which are sensitive to reduction-oxidation conditions in the sediment; and characterization of sterols and lignin phenols, which are biomarkers indicating the sources and fate of organic matter in the sediment. With the aforementioned work on foraminifera to complement these physical and geochemical analyses, the scientists hope to distinguish historical low-oxygen events from more modern processes and may also gain insight into how climate change might impact habitats and ecosystem health in Hood Canal.

Related Sound Waves Stories
Scientists from Four USGS Science Centers Collaborate in Study of Coastal Groundwater Exchange in Hood Canal, Washington
Jan. / Feb. 2013
Studying Submarine Ground-Water Discharge at Santa Barbara, California, and Hood Canal, Washington
August 2006
Scientists Go Deep to Track Algae-Feeding Nitrogen in Washington State's Hood Canal
July 2006

Related Websites
R/V Centennial: Detailed Specifications of Research Vessel
UW Friday Harbor Laboratories
Gallery of Common Sediment Sampling Devices—Grab Samplers

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cover story:
Exploring Undersea Terrain Off the Northern U.S. Atlantic Coast

Autonomous Kayak Performs Shallow-Water Surveys

Natural Versus Human Impacts on Marine Ecosystems in Hood Canal

Research Research to Support Hurricane Sandy Rebuilding Gets Boost from Supplemental Funds

Unprecedented Rate and Scale of Ocean Acidification in Arctic

Special Issue of Marine Geology Focuses on San Francisco Bay Coastal System

"Native Youth in Science—Preserving Our Homelands" Completes Year Two

Michael E. Field Honored by U.S. Coral Reef Task Force

Barbara Lidz Steps Down as Sound Waves Contributing Editor

Award-Winning Student Intern Experiences Life at the USGS

Coastal and Marine Geology Program Contributes to "Feds Feed Families"

Publications Nov. / Dec. Publications

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