Exploring the dead zone of the Saanich Inlet

UVic project collecting data from water in the Inlet; interest in the research generated around the world.

Undergraduate student Erinn Raftery and UVic researcher Jeff Sorensen adjust the equipment used to collect water samples in Saanich Inlet.

More dead zones are popping up all over the world as areas of ocean, once teeming with life, suddenly see dramatic losses of fish and other species.

Researchers are asking why this is happening and how domestic scientists and fishermen alike can adjust. To get those answers, people are turning to the Saanich Inlet.

Since September, a research team on the University of Victoria vessel MSV John Strickland, has been going in the inlet, collecting water samples at various depths. The project, led by UVic postdoctoral researcher Jeff Sorensen, is using the Saanich Inlet’s natural dead zone to establish a baseline of what goes on there.

A dead zone, he explained, is when a body of water uses up a significant amount of its oxygen. Once that oxygen is gone, marine life can no longer sustain itself there. In the case of Saanich Inlet, Sorensen said its dead zone properties have existed for years, due to a shallow sill at its entrance from the Salish Sea. When water flows in during the fall months, the oxygen is replenished and marine life flourishes for a few months. The oxygen is, however, used up. This means the inlet has little to no oxygen for most of the year.

Sorensen said this project is examining what happens in the water as the oxygen vanishes and the impact on marine life. He said dead zones are typically caused by the warming of the water.

“Hotter water can hold less oxygen,” he said, adding human activity is generally seen as a contributing factor to this warming. “We can expect water temperatures to increase and see more oxygen loss in various parts of the world.”

Sorensen said North American waters are not seeing the proliferation of dead zones as much as, for example, the Mediterranean Sea. There, dead zones are having a serious impact on traditional fishing areas. The dead zone conditions in the Saanich

Inlet, he added, are nothing to worry about, as they’ve existed for years.

This research has drawn the attention of oceanographers from around the world. The 30-member UVic research team is spending eight months making trips to the inlet every two weeks. Their water samples are in demand among other research groups from Switzerland, Ireland, Spain, Brazil and elsewhere. UVic has partnered with Ocean Networks Canada and Fisheries and Oceans Canada, as well as researchers from U.S. and U.K. universities to run the project. It’s being funded by the Canadian government’s Natural Sciences and Engineering Research Council.

Sorensen said Saanich Inlet is a natural lab and provides convenient access to the conditions they need, which makes it an attractive area for research.

“It’s a place that allows researchers to look at what’s happening down there, and therefore in typical dead zones around the world.”

The Inlet has been studied for between 40 and 50 years, Sorensen said, giving scientists and others a good idea of what happens there. The data they collect will offer researchers around the world a starting point on which to gauge local conditions.

This project, says UVic, is the first time that such a wide range of measurements are being taken over the duration of the Inlet’s oxygen depletion process.