NOAA's Response and Restoration Blog

An inside look at the science of cleaning up and fixing the mess of marine pollution

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An Estuary in the Shadow of Seattle

People working at marsh's edge.

Volunteers help restore the Duwamish River by planting native vegetation at an Earth Day event hosted at Codiga Park, April 2008. (NOAA)

Update: It’s been announced that a proposed settlement was reached with Seattle to resolve its liability for injured natural resources. Seattle has purchased restoration credits from Bluefield Holdings Inc., a company that develops restoration projects. The city’s credit purchase totals approximately $3.5 million worth of restoration. This is the first natural resource damages settlement to fund restoration through the purchase of credits by a restoration development company. For more details:

What makes river water flow in one direction in the morning and change direction in the afternoon? Tides.

Where the Duwamish River meets Puget Sound in Washington state this shift of water flow happens daily. The Duwamish pours into the salty waters of Puget Sound, making it Seattle’s downtown estuary. The powerful tides that fill and drain the sound push and pull on the Duwamish causing a shift in directions at the river’s estuary.

This estuary does not look like the estuaries from high school text books. It no longer has a wide delta where the freshwater river fans out to meet the salty ocean. Instead, it looks like a channelized waterway. Almost all of the Duwamish estuarine wetlands and mudflats have been lost to dredging or filling for industrial purposes. Restoring the Duwamish‘s estuary is a massive challenge—requiring government agencies, industry, and the public to work together.

Aerial view of city with river.

Aerial photograph of the Lower Duwamish River. Harbor Island and Elliott Bay are shown in the top left and downtown Seattle in the top center of the photograph. (NOAA)

I am happy to report a significant step forward in this collaboration. NOAA recently produced key answers to some tough questions, based on lessons we learned as we worked on this restoration effort: What works the best to restore this highly urban and developed river and estuary? What are some of the key obstacles we encountered?

Main challenges for restoring the Duwamish:

  • Dealing with costs and challenges of existing contamination
  • Preventing erosion of new restoration
  • Keeping newly-planted vegetation alive—geese and other wildlife love to eat newly planted restoration sites

Key lessons learned for successful restoration:

  • Plan for uncertainty: the most common issue for restoration in urban areas is discovering unexpected challenges, such as sediment contamination during construction.
  • Allow for ongoing maintenance: Restoration isn’t over just because a project is complete. To ensure the long-term success of restoration efforts, continued stewardship of the site is necessary and should be included in project planning.
  • Get the biggest bang for your buck: When companies conduct cleanups of their sites, it is most cost effective to conduct restoration at the same time.
River with grid strung above it.

Geese inside goose exclusion fencing at Boeing Project. (Credit: Boeing)

The challenges and recommendations are only a snapshot of what can be found in the NOAA report, Habitat Restoration in an Urban Waterway: Lessons Learned from the Lower Duwamish River. While the Duwamish estuary may look nothing like it did historically, it is important to always be reminded that it is still full of life. From salmon to kayakers to industry, the estuary serves a key role in the Seattle community. Learn more about what we are doing to restore the Duwamish River.

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Restoring Marsh Habitat by Sharing Assessment Techniques

Group of four people stand in a marsh.

Training participants examine a one meter square quadrant transect (rod at bottom) to illustrate how new metrics could be applied for a northeast assessment. (NOAA)

There is no one-size-fits-all approach to environmental assessments for oil spills or hazardous waste events. We must therefore custom-tailor our technical approach for each pollution incident.

We first determine whether impacts to natural resources have occurred and whether it is appropriate to proceed with a Natural Resource Damage Assessment (NRDA). We collect time-sensitive data, evaluate available research and information about the type of injury, and determine what species and habitats are likely to have been affected. If we determine that habitats, wildlife or human uses have been harmed or could experience significant impacts, we often proceed with a full damage assessment.

This type of scientific assessment is particularly challenging in a marsh environment given potential injury due to both oil persistence and toxicity. For example, a home heating oil released by the North Cape barge in 1996 caused acute injury to lobsters, clams, fish, crabs, and mussels in, and adjacent to, the marshes of southern Rhode Island. The light oil was highly toxic, but quickly dissipated, thereby causing a lot of immediate injury, but less long-term problems. By contrast, a more chronic impact was the result of persistent fuel oil released by the Barge Bouchard 120 in the salt marshes of Massachusetts in 2003. That oil saturated 100 miles of shoreline, impacting tidal marshes, mudflats, beaches, and rocky shorelines. These evolving factors are why we constantly share best practices and lessons learned among our colleagues in the northeast and nationwide.

Members of the Northeast and Spatial Data Branch of NOAA’s Office of Response and Restoration and NOAA’s Restoration Center recently met at Spermaceti Cove, Sandy Hook, New Jersey, to participate in a hands-on workshop to improve our salt marsh damage assessment techniques and data compilation.

They were building on previous findings presented at a 2015 salt marsh assessment workshop in Massachusetts, that information learned there should be shared in other locales. Of note were the variety of vegetation and native invertebrates around the coastal United States that necessitate region-specific marsh field training.

Two people standing in shallow water holding a seining net.

Scientists seining salt marsh tidal channel collecting native small fish for injury determination. (NOAA)

To address the study of natural resource damages in a mid-north Atlantic salt marsh environ, this 2016 effort included the count of flora and fauna species within a 2 meter square quadrant along a designated transect (see photo) to provide a measure of diversity and species richness.  Also they used a seine, a lift net, and minnow traps to collect fish adjacent to the marsh for species identification and to measure body size and observe possible abnormalities, both external and internal.

Additionally, NOAA scientists discussed and demonstrated current best practices to perform our work regarding health and safety, sample custody, and data management.

In an actual future marsh injury assessment, the Trustees would develop a conceptual site model for guidance in testing the hypotheses, the specific study design, and the proper site and habitat injury measures.

Ken Finkelstein and Kathleen Goggin of NOAA’s Office of Response and Restoration contributed to this article.

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What Scientists Learned About Cleaning up Oil Spills by Covering a Delaware Beach with Oil — on Purpose

Barrels and workers on a beach.

Delivery of barrels containing Bonny light Nigerian crude oil. Oil was weathered in a separate pool. (NOAA)

Most people don’t want to spill oil onto beaches. But after the disastrous 1989 Exxon Valdez spill covered the remote, rocky beaches of Alaska’s Prince William Sound with crude oil, Al Venosa was itching to do exactly that.

As an environmental scientist with the U.S. Environmental Protection Agency (EPA), Venosa had been called up to Alaska to help study the Exxon Valdez oil spill and its cleanup. In particular, he was interested in an oil spill cleanup technique that was getting a lot of attention at the time—an approach known as “bioremediation.” It involved adding oil-eating microbes and extra nutrients to an oiled beach to accelerate the natural background process of microbes breaking down, or biodegrading, oil.

But Venosa wasn’t satisfied with the research attempts that came out of that spill. He wanted to set up a more scientifically rigorous and controlled study of how effective bioremediation was under realistic conditions in the marine environment. However, in the United States, getting permission to spill oil into the environment on purpose is a very difficult, and nearly impossible, thing to do.

Coming Together

Meanwhile, Ben Anderson, an oil spill biologist with the Delaware Department of Natural Resources and Environmental Control, had also been working on the cleanup after the Exxon Valdez oil spill. Just a couple months after that iconic spill and shortly after he returned home from Alaska, he had to deal with a spill of hundreds of thousands of gallons of bunker oil when the T/V Presidente Rivera ran aground in the Delaware River. He remembered 1989 as a tough year for oil spills. Anderson began wondering how to improve the efficiency of oil spill cleanup and better protect Delaware’s abundant natural resources.

A few years later, in 1993, Anderson was listening to Ken Lee from Fisheries and Oceans Canada as he presented on bioremediation at the International Oil Spill Conference. At the end of his presentation, Lee mentioned how important—and difficult—it was to do controlled field studies on bioremediation. The comment got Anderson thinking; maybe he could help make this happen in Delaware.

“Anything we can do to improve the aftermath of an oil spill in Delaware,” recalled Anderson.

After the presentation, he approached Lee, who introduced him to Al Venosa. The pair decided to work together to bring Venosa’s meticulous research approach to a study of oil bioremediation on Delaware’s beaches.

“From that time to next summer, I worked on getting a permit with EPA and with the state,” said Anderson. He and his collaborators also reached out to local environmental groups in Delaware and to NOAA, U.S. Fish and Wildlife Service, and other agencies to build support for the research project, building in as many safeguards as possible to limit any potential environmental impacts.

One issue the research team would have to work around was the fact that each May, Delaware’s sandy shores are crawling with horseshoe crabs, a prehistoric marine creature with armor and a long, pointy tail, which comes ashore to lay its eggs. More than 20 species of birds, as they migrate north to nest in the Arctic each summer, stop along these shores to nourish themselves with a feast of horseshoe crab eggs. To avoid interfering with this ecological phenomenon, Anderson and Venosa would have to start the experiment after horseshoe crab spawning season had passed.

Oil Ashore

With just a few days left before the experiment was to begin on July 1, 1994 and with Venosa and his colleagues at EPA and the University of Cincinnati already on the road from Ohio to Delaware, Anderson finally secured the needed permit.

Permissions in hand, the researchers set up the experiment very carefully. Unlike previous studies, they focused intensely on replication and randomization. They cordoned off five separate blocks of sandy beach on Delaware Bay, so that each block was parallel to the ocean yet would still be within reach of the tides.

Oiled test plots on a beach.

View up beach of the 20 oiled plots. (NOAA)

Within each block, they randomly assigned three oil treatment plots and one control plot, which was sprayed with only seawater. Plots undergoing the three oil treatments, after having weathered crude oil applied at the very beginning, were sprayed daily at low tide with seawater and nutrients (nitrogen and phosphorus), nutrients and oil-eating microbes, or nothing extra (essentially, only oil had been applied). This meant that each treatment and control was replicated five times, reducing the chance that human error or natural variation would skew the results.

“We grew up our microorganisms on the beach in 55 gallon drums using the same seawater, nutrients, and microorganism [species],” recounted Venosa, who served as the lead researcher for the study. “We added them back onto these plots every week, continuously growing and adding them. These [microbes] were adapted to the oil we used and to the climatic conditions at the site.”

As a precaution, the research team strung oil containment boom along the waters surrounding the experimental plots to catch any oil runoff. In addition, they lined up cages of filter-feeding oysters in the surf off of each study block, as well as farther up and down the shoreline, to act as natural oil monitors. NOAA ecologist Alan Mearns helped facilitate this monitoring and multiple toxicity studies to determine the potential toxicity of the various treatments over time.

Bioremediation for the Birds?

Fourteen weeks later, what did they find? According to one of the study write-ups published at the 1997 International Oil Spill Conference, the researchers found that:

“oil was lost naturally because of both physical and chemical processes and biodegradation, that degradation of oil alkanes and PAHs [polycyclic aromatic hydrocarbons] in upper intertidal sandy sediments could be enhanced with the continuous addition of dissolved nutrients, that treatment with oil-degrading bacteria provided no additional benefit, and that treatment neither enhanced nor reduced the toxicity of the oil.”

While the team did detect a boost in how quickly oil broke down in plots sprayed with nutrients (which fed naturally occurring microbes), it was a pretty minor benefit in the big picture of oil spill cleanup. And adding more microbes didn’t increase the rate of oil breakdown at all.

Delaware Bay’s waters are already rich with nutrients—and oil-eating microbes. “It was probably a lot of runoff from fertilizer from agriculture and wastewater treatment plants,” speculated Venosa. “We had a two to three times increase in the rate of biodegradation.”

However, for an area like Delaware Bay with high background levels of nutrients, Venosa wouldn’t recommend going to the trouble and cost of using bioremediation techniques, unless a spill happened right before something like the annual horseshoe crab spawning and bird migration.

“What we found was you don’t have to do any more nutrient addition,” said Anderson. “Just keep adding ambient water and keep it aerated to get the [biodegradation] benefit. Let nature take its course, but give it a little hand by keeping it wet on the beach face.”

Scientific Success

Overall, the research team considered the experiment a success. They finally had hard data, meticulously gathered, that showed bioremediation to be a “polishing technique,” to be potentially used in oil spills when the local conditions were right and only after other, quicker-acting cleanup methods had been applied first. If an area showed high local levels of nutrients and oil-degrading microbes, bioremediation likely wouldn’t be very effective.

“I was expecting more of a quantifiable effect in biodegradation, but I didn’t realize the nutrients were going to be relatively high in the background,” reflected Venosa. “I was expecting to see somewhat similar increases in the field as in the lab. In the laboratory, it’s different because your controls don’t have any nutrients, so whenever you add nutrients that are in excess of what they need to grow, you’ll see huge increases.”

As a result of this and subsequent studies in Canada, the EPA released guidance documents on implementing bioremediation methods in different environments, such as marine shorelines, freshwater wetlands, [PDF] and salt marshes.

These days, however, bioremediation is starting to mean more than just adding microbes or nutrients, and now includes a range of other products meant to stimulate oil-degrading activity. How well do they work? More research is needed. But not since 1994 on the shores of Delaware Bay has the United States seen another field experiment that has intentionally released oil into the environment to find out. That summer was a unique opportunity for oil spill scientists to learn, as rigorously and realistically as possible, how well a certain cleanup method could work on an oil spill.

For more information read:

Field-Testing Bioremediation Treating Agents: Lessons from an Experimental Shoreline Oil Spill (1997, Alan Mearns et al)

Bioremediation Study of Spilled Crude Oil on Fowler Beach, Delaware


This post was written by Dr. Alan Mearns.

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Bay Long Oil Spill in Louisiana

Woman looking out at water with boom floating in it.

Overseeing cleanup operations on Chenier Ronquille Island. (U.S. Coast Guard)

On September 5, 2016, a marsh excavator operated by Great Lakes Dredge and Dock Company tracked over pipeline while performing restoration activities in Bay Long, a sub-estuary of Barataria Bay, discharging approximately 5,300 gallons of crude oil into the Gulf of Mexico. The pipeline was shut in and is no longer leaking. The incident occurred at an active restoration site for the Deepwater Horizon oil spill. The cause of the incident is still under investigation.

NOAA’s Office of Response and Restoration has been providing scientific support including trajectories and fate of oil, resources at risk, information on tides and currents, and technical guidance towards the response. Other roles provided by NOAA are guidance on Shoreline Cleanup and Assessment Technique (SCAT), a systematic method for surveying an affected shoreline after an oil spill, as well as data management and updates through Environmental Response Management Application (ERMA®). OR&R’s Emergency Response Division has a team of six on site.

For more information, read the September 11, 2016 news release from the U.S. Coast Guard.