LAPUSH – Scientists say more research is needed off the Washington coast to determine whether a seasonal fish kill is normal, increasing or predictable.
Last year, thousands of dead rock fish and crabs washed ashore in the Quinault reservation south of LaPush.
Similar die offs have been reported on the Oregon coast each summer for five years.
The phenomena, attributed to an area of water with low dissolved oxygen, is called a hypoxic zone.
But it goes by another, more eerie name: ‘dead zone.’
Aquatic creatures breathe by pulling oxygen out of the water with their gills.
If the amount of dissolved oxygen in the water is too low, the animals suffocate.
Liam Antrim, a marine biologist with the National Oceanic and Atmospheric Administration’s Olympic Coast National Marine Sanctuary in Port Angeles, said he and other scientists have a theory as to the hypoxic zone’s cause.
“The wind in particular is pushing the water around on the surface of the ocean,” Antrim said
“As that gets moved and displaced, it is drawing water from down deep to replace it.”
Deeper water is colder, denser and saltier than surface water, and therefore usually contains less dissolved oxygen, he said.
Similar dead zones in the Gulf Coast and in the Hood Canal have been blamed largely on agricultural runoff.
Fertilizers and organic material enter the water and cause an explosion in the population of small organisms like phytoplankton and zooplankton.
The single-celled organisms die, sink to the bottom, and their decay absorbs oxygen out of the water.
The agricultural theory “seems really unlikely on the outer coast because there’s not that much agricultural activity,” Antrim said.
The low oxygen levels are normal in deep ocean troughs and in deep lakes, like the fjord-carved Lake Crescent.
But Antrim and others are unclear how normal the dead zone on the coast is.
“What’s perhaps a little abnormal is the timing and duration of these wind patterns that are pushing the surface water around, and bringing the deep water,” Antrim said.
“We really don’t know what the normal cycle is.”
This summer, Antrim and other researchers at the Port Angeles office, plan to place 10 buoys off the Olympic Coast to measure dissolved oxygen.
From 2001 to 2004, the sanctuary’s scientists were measuring dissolved oxygen in person from a boat.
Starting in 2004, buoys were equipped with the oxygen sensors.
The buoys provided more data more often.
“We really are limited in our understanding of this one because we don’t have the long term sampling database,” Antrim said.
He said that after at least five years of data, he and others can decide what is a normal occurrence of the hypoxic zone, and what is abnormal.
Bob Steelquist, the sanctuary’s education coordinator, said last year, when the dead zone off the Oregon coast received national attention, many people called him to ask if the problem was occurring in Washington.
He tried to answer, but was not sure, he said.
“What’s missing for us is the eyes and ears in the water so we’re able to capture it and understand if there’s a trend, or an isolated incident,” Steelquist said.
