Science and Technology for Canadians

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Summary

Following the 1989 Exxon Valdez oil spill, a bioremediation strategy based on nutrient enrichment was used to clean up over 100 kilometres of contaminated shoreline. Scientists from the Department of Fisheries and Oceans had previously learned that the crude oil spilled on sandy beaches of Nova Scotia wasn't breaking down because of poor soil conditions. Low nutrient concentrations were found to limit the rate of oil degradation by natural bacteria within the sediments. Fertilizer was added to improve the soil and it worked.

The development and evaluation of bioremediation strategies for oiled wetlands is now the focus of a joint study by DFO and the US Environmental Protection Agency. Salt marshes are a habitat for all kinds of wildlife and the nursery of the ocean fisheries. When the study is completed in 2002, scientists will have a better understanding of how salt marshes recover from oil spills and which of the treatment strategies are best for helping to speed natural recovery.

Transcript of Video

Gillian Deacon
Everyone's heard of the 1989 Exxon Valdez oil spill... but who knew about the Canadian science that was used to clean it up?

Kenneth Lee
On a large scale this technology was used to clean up part of the Exxon Valdez spill in Alaska. There were over 100 kilometres of beaches that were actually cleaned by using nutrient amendments in Valdez following the spill.

Gillian Deacon
In 1985, four years before the infamous Alaskan oil spill, Canadian scientists were studying the impact of spills on sandy beaches in Nova Scotia. When they used fertilizer, they found that it encouraged the growth of the bacteria that break crude oil down naturally. Whether fertilizer will do the trick in wetlands is the focus of a joint study by Fisheries and Oceans Canada and the US Environmental Protection Agency. Not only are salt marshes a habitat for all kinds of wildlife, they're also the nursery of the ocean fisheries. It's important to know what to do in this delicate ecosystem in the event of an oil spill. In June of 2000 at Petpeswick Inlet in Nova Scotia, a controlled spill started the experiment.

Kenneth Lee
What we're looking at in our study is how does a wetland recover naturally. And we can't do this following an oil spill because it's patchy... and so here we come to a wetland and we can actually apply the oil evenly so we can do scientific measurements to really understand what are the natural rates of recovery in a wetland, and what can we do to speed up the recovery of a wetland?

Gillian Deacon
The experimental plots are treated in different ways to study which approaches speed natural recovery the most. Where fertilizer is used, it's hoped that it'll encourage the growth of plants and oil-degrading bacteria. Plants may contribute to recovery because their roots provide little ecosystems that harbour bacteria.

Cutting the plants down as soon as they grow will show how well the fertilizer stimulates bacterial growth in the absence of plants.

Oxygen is essential to oil-degrading bacteria. This plot is tilled regularly to see if it introduces more oxygen into the sediment.

To study how a salt marsh recovers on its own, this plot was oiled and left undisturbed. There are also unoiled plots, fertilized or not, for comparison. Sediment and plant samples from all the plots are collected every two weeks for testing.

Bioremediation relies on living things to clean toxins up. But there's no such thing as a super bug. Crude oil is made up of thousands of compounds, and it takes many different kinds of naturally occurring bacteria to break it down. Various lab procedures identify and count the bacteria, and monitor how well the oil is degrading. Less oil and more bacteria are signs of recovery.

Kenneth Lee
In terms of bioremediation, by the addition of nutrients, we've shown conclusively that it's quite effective in sand beaches and gravel beaches. There's no doubt about that. What we're looking at now is extending this treatment to wetlands and unfortunately I can't show you the results from this study at this time because we've just started the experiment but in our previous experiments we found that we could achieve what nature does in about 10 years, in one summer.

Gillian Deacon
By 2002, when the study is completed, scientists will have a better understanding of how salt marshes recover from oil spills, and which of the tested strategies are best for helping to speed natural recovery.

Earth Tones is produced in co-operation with Fisheries and Oceans Canada.