The spineless denizens of the pitch-dark sea floor at the bottom of Port Valdez were utterly decimated by submarine landslides and scouring tsunamis during the 1964 Good Friday Earthquake.
But worm by worm, clam by clam -- snail by snail -- they slowly crept back.
And now, after decades of disruption and slow re-colonization, the marine invertebrates have collectively repopulated the abyss with a stable ecosystem, according to a team of Alaska scientists at the School of Fisheries and Ocean Sciences at the University of Alaska Fairbanks.
"Four decades of monitoring, including samples collected last year, have confirmed that the sea floor now resembles that of an undisturbed glacial fjord," reported UAF researcher Arny Blanchard in a story posted last week.
"The earthquake, which measured 9.2 on the Richter scale, and the tsunami waves that followed, impacted every marine community in Prince William Sound."
The findings arose from the Port Valdez study, a four-decade long effort to monitor the health of marine life at the head of Valdez Arm, location for the terminus and oil-loading facility of the Trans-Alaska Pipeline.
One focus of the project — funded by Alyeska Pipeline Service Company — is to keep tabs on how discharges of wastewater and treated ballast water from the pipeline terminal might be impacting seafloor life. In this case, the scientists concluded: Not much.
"Scientists say that effects on animals on intertidal beaches and the sea floor from wastewater discharged by the terminal have been minor," the story reported.
The seafloor study was published in the journal Marine Environmental Research. Along with Blanchard, the other authors were longtime UAF researchers Howard Feder and Max Hoberg.
"The findings shed light on how long it takes for seafloor ecosystems to recover after earthquakes," the story explained.
"The 1964 earthquake and resulting tsunami wreaked havoc on intertidal beaches and seafloor of Port Valdez, according to Feder, the leader of the biological component of the project from 1971 to 1990."
Destruction by the second biggest temblor
Alaska's great quake ruptured at 5:36 p.m. on March 27, 1964, about 15 miles below the surface of College Fiord some 45 miles west of Valdez. A section of the Pacific tectonic plate about half the size of California lurched a few meters deeper beneath the North American continental plate and triggered four to six minutes of violent shaking. The magnitude was later estimated at 9.2 — the second most powerful quake yet measured on Earth.
In Valdez, the motion disrupted and destabilized unconsolidated glacial outwash deposits that underlay the city, its waterfront and harbor — a delta of gravel and silt and sand deposited over eons on a steep slope descending into Valdez Arm.
All at once, 98 million cubic yards of material — the equivalent of 19 million dump truck loads — sloughed into the abyss. It sucked about 500 feet of the Valdez waterfront with it.
Two big piers, wharfs and docks, whole buildings — and at least 20 adults and seven children who had come down to greet the arrival of the steamship Chena — all disappeared into the maelstrom.
"I saw people running with no place to run to. It was just ghastly," later wrote M.D. Stewart, captain of the Chena. "They were just engulfed by buildings, water, mud, and everything."
There were other submarine landslides in the Port Valdez that afternoon, along with repeated tsunamis that inundated the old town site and overran beaches. The seiche waves ripped intertidal life from the shore, while an immense avalanche of sediment buried much of the fiord's bottom, 600 to 800 feet down.
What happened next set in motion 26 years of ecological flux for the port's benthic creatures, the authors said.
"This caused the whole community of bottom-dwelling marine invertebrates — such as sea worms, snails and clams — to change."
"Some seafloor invertebrates usually found in glacial fjords like Port Valdez, such as the sea worms Terebellides stroemi and Galathowenia oculata, virtually disappeared. Other animals took advantage of the disturbance and colonized the area."
One interesting finding credits the Solomon Gulch Hatchery for literally fertilizing the process. Since the hatchery began operations across the bay from the new city of Valdez in 1982, millions of fish, mostly pink salmon, return to the port each season, the scientists said.
"There are too many returning adult salmon to fully harvest, so many salmon die in the fjord and their carcasses are deposited in the intertidal or settle on subtidal sediments," they wrote.
Year after year, their carcasses melted into the gravels, delivering nutrients to the sea worms and other gooey critters of the sea floor, and helped the deep, dark ecosystem beneath Port Valdez rebound and stabilize.
Contact Doug O'Harra at doug(at)alaskadispatch.com