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by Valerie Shore
A research team is using creative ways to measure
what’s going
on in the Strait of Georgia.
Cross the Strait of Georgia by ferry over the next few years and
there’s a good chance you’ll be conducting oceanographic
research.
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| Dower and a new underwater instrument that automatically counts and sizes plankton. (Darren Stone photo) |
Well, not you personally. Below you, deep in the bowels of the
ferry, sophisticated instruments will be measuring water conditions
as the vessel plies back and forth across the strait. What those
instruments reveal may one day help fisheries managers predict changes
in fish abundance.
“Our goal is to find out what it is that makes the Strait
of Georgia a particularly good environment for fish in some years,
but bad in other years,” says Dr. John Dower, a fisheries
oceanographer in UVic’s department of biology and school of
earth and ocean sciences. He’s part of a new research initiative
known as STRATOGEM —the Strait of Georgia Ecosystem Modelling
project—which seeks to understand the complex physical and
biological dynamics at work in the strait.
“The Strait of Georgia is one of the most productive areas
on the B.C. coast, yet we know surprisingly little about how it
works,” says Dower. To get some answers, he and STRATOGEM
partners at the University of British Columbia and the Department
of Fisheries and Oceans are focusing on three key physical processes:
the Fraser River outflow, which carries vital nutrients; windstorms,
which mix the water; and inflow from the open ocean, also a rich
source of nutrients.
These processes combine to make conditions ideal or poor for the
growth of plankton, the microscopic plants and animals that form
the base of the marine food chain. “We want to untangle how
these processes condition the water column to be good or bad for
plankton growth,” says Dower. “Then we’ll use
ecosystem modelling to come up with rules about what makes a good
or bad year for fish.”
But first they need the data. A major problem with marine field
work is getting out on the water often enough. The team has come
up with two creative solutions. One involves B.C. Ferries. By this
spring, a ferry on each of the three main routes crossing the strait
will be equipped to measure water temperature, clarity, salinity,
and nutrient and plant-life content. “We’ll get snapshots
of what’s happening in the surface waters several times each
day,” says Dower.
To get the deeper picture, the STRATOGEM team goes out monthly
to nine test sites around the strait, where plankton and water samples
are taken from surface to seafloor.
“The strait is such an active place, with tides, currents
and the Fraser River plume, that we need to work as quickly as possible,”
explains Dower. A traditional ship would do the circuit in two days.
But a Coast Guard hovercraft, whisking along at about 80 kph, does
the job in eight hours.
By the end of the four-year project, the team hopes to have enough
data for predicting trends in productivity in the strait. Fisheries
managers can then incorporate these factors into their models for
such things as predicting salmon returns.
The STRATOGEM project is funded by the Natural Sciences and Engineering
Research Council.
Not all plankton are created equal. And this is what makes John
Dower’s part in the STRATOGEM research so challenging.
Dower wants to know how physical processes in the Strait of Georgia
affect the amount and distribution of plankton in the water. More
plankton can mean more food for fish.
“My lab is looking at how plankton distribution changes
through the seasons across the sites we’re measuring in the
strait, and how we can link those changes back to the physical measurements
that my colleagues at UBC are interested in,” says Dower.
For years, it was believed that the classic marine food chain
goes in a linear fashion from large phytoplankton (plant plankton)
known as diatoms, to zooplankton (animal plankton). They in turn
get gobbled by small fish, which become dinner for larger fish,
and so on.
But it’s not always that simple. In years with fewer windstorms,
smaller phytoplankton known as flagellates predominate. They aren’t
big enough to interest the zooplankton that fish feed on. So another
step is added to the food chain to produce things big enough for
the fish to eat. And that’s not a good thing. “The more
steps in the food chain, the less energy there is at the top for
the fish,” says Dower.
That’s why precise measurements of phytoplankton species
and abundance are so critical. “In some years, conditions
combine to create the right phytoplankton at the right time, which
can lead to good fish food. That’s the argument we’re
trying to make.”
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