Puget Sound in Bloom: Killer Cornflakes
Puget Sound in bloom: Invasion of the killer ‘corn flakes’
Down at the Marine Science Center at Point Wilson, Kristin Wilkinson’s normal job is to guide visitors into the silent, whimsical world of plankton.
Kids love to watch her dip an 18-inch plankton net into the bay alongside the dock, carry her jar of seawater back to the lab, then apply a couple of drops to a glass slide. From there, she leads her visitors down the rabbit hole into a microscopic Wonderland.
Magnified a hundred times or so, that drop of water reveals a strange and
marvelous micro-universe of tiny plants and animals in every imaginable shape and color. There are bug-like critters with spindly antennae, twisted chains of golden-brown diatoms, miniature shrimp-like crustaceans with wriggling tails, elegant necklaces of colorful dinoflagellates...
This microscopic zoo is a reminder that the waters off Puget Sound are some of the most productive on earth, teeming with life that we rarely see, but which serves as the basis for the marine food web.
These days, however, Kristin Wilkinson’s task is more sobering. An Americorps volunteer with a degree in marine biology, she finds herself doing sentry duty, on the lookout for a biological invasion of microscopic fish-killers.
Scientists around the region are tracking a massive bloom of a tiny, single-celled algae they call Heterosigma. In the past week, the infestations – scientists call them “harmful blooms” – have been detected at Port Angeles, where water samples showed concentrations of more than 2.5 million cells per liter of seawater. Similar blooms were found as far north as Cypress Island, where the algae is believed to have killed thousands of fish in net pens.
Anne Murphy, the science center director, says her staff is busy collecting and analyzing water samples from Port Townsend piers and from Mystery Bay. A volunteer is doing daily flyovers, looking for telltale bands of rust-brown water that signal something is amiss.
As of the weekend, the main blooms had not rounded the corner into Admiralty Inlet. But scientists fear that this week’s powerful tides could help wash the problem into Port Townsend’s lap.
“So far so good, but it’s not over until it’s over,” says Dr. Jack Rensel, a contract scientist and plankton expert who works with state and federal officials to monitor what they call “harmful blooms.”
“Everything hinges on the weather and the tides,” he said. “Some cloudy, windy weather certainly would help.”
Heterosigma is a single-celled organism, typically about 25 microns, or 1/1000 if an inch wide. Seen through Wilkinson’s microscope, it’s quite splendid, an ovoid of mottled shades of brown and gold, with two long, hair-like appendages that whip the water to provide propulsion. With no cell wall, each organism adopts a slightly different shape, giving it the rumpled texture that one prominent biologist compares to an elegant “corn flake.”
Like most plankton, Heterosigma winters in a state of semihibernation, then comes to life in the spring, when it whips those tiny flagella and swims toward the surface. There it lives a life not unlike a garden shrub, collecting nutrients and photosynthesizing them with chlorophyll.
In a normal year, Heterosigma poses no problem – not to humans, nor to sealife. Just another member of the planktonic family.
But under certain conditions, usually in the long warm days of late June and early July, these critters go downright nuts. Those cells multiply at a phenomenal rate, reaching concentrations that kill fish – especially salmon and other fish confined in net pens or wild fish in shallow water such as river mouths and long inlets such as Hood Canal.
This is nobody’s fault, Rensel says. . The outbreaks appear to be completely natural, not caused by pollution or any other human activity.
And scientists aren’t quite sure how it kills fish, he says. “It’s not the classic toxin, but it produces hydrogen peroxide that affects the fishes’ gills and shuts down their respiration.”
Rensel and other scientists were not completely surprised by this year’s Heterosigma bloom. Blame it on nice weather. Unusually warm, calm weather in late June, and a strong freshwater run-off from Northwest rivers, especially the Fraser River south of Vancouver, BC., created conditions just right for an algae bloom.
Those conditions lead to “stratification” – plenty of ocean nutrients for food, and a layer of less-salty water at the surface, which breeds microscopic plankton. Cloudy, windy weather help mix local waters and break up any harmful blooms.
Heterosigma blooms have been observed around Puget Sound for at least 40 years. There was a major outbreak around Lummi Island in the late 1960s, fish kills in Puget Sound in 1989, 1991 and 1997.
Fisheries research or commercial net pens are especially vulnerable, because they are confined near the surface along with the blooms. “Fish farmers are constantly watching the water,” Rensel says. “They learn how to spot these blooms from the air.”
As of last weekend, the blooms around Cypress Island had subsided, he says. But Puget Sound will remain at risk for a while – or until the area gets some clouds and wind to break up those trillions of tiny corn flakes.
Fortunately, Heterosigma’s many evolutionary cousins will remain. Puget Sound’s plankton explodes in the spring, clouding the water and fueling the complex food web that supports everything from herring and candlefish to Orca whales and sixgill sharks.
That bloom lingers through the summer and well into the fall. Later this month, the full moon will wane and local kayakers will take to the water at night, each paddle stroke triggering a fireworks show of luminescent critters.
And down at the Marine Science Center, Kristin Wilkinson and friends can resume their normal tours into Wonderland.
