It took 26 years for marine invertebrates living on the Port Valdez seafloor to stabilize after Alaska's Great Earthquake of 1964, according to a scientist at the University of Alaska Fairbanks.
"The earthquake, which measured 9.2 on the Richter scale, and the tsunami waves that followed, impacted every marine community in Prince William Sound," said Arny Blanchard, a research assistant professor at the UAF School of Fisheries and Ocean Sciences. Four decades of monitoring, including samples collected last year, have confirmed that the seafloor now resembles that of an undisturbed glacial fjord.
Blanchard's findings, along with those of Howard Feder, UAF professor emeritus, and Max Hoberg, UAF researcher, were published in the journal Marine Environmental Research. The findings shed light on how long it takes for seafloor ecosystems to recover after earthquakes.
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. Marine plants and animals on Port Valdez beaches were destroyed by the tsunami while the earthquake deposited massive amounts of sediment on the seafloor. 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 of those animals is a family of sea worms called Capitellidae. They became unusually dominant in the region for a few years. According to Blanchard, Capitellidae are known for being highly opportunistic and tolerant of disturbance.
The diversity and abundance of marine invertebrates in Port Valdez was highly variable from 1971 to 1989 compared to other glacial fjords, primarily as a result of the earthquake. Over time, the community of animals stabilized. Today, the balance of bottom-dwelling animals looks more like an undisturbed glacial fjord.
"The ecosystem was in such flux that responses by seafloor communities to regional climatic variability were masked by the recovery process," said Blanchard.
Samples collected in 2010 marked the fourth decade of sampling in Port Valdez, making it one of the longest-running research projects at the UAF School of Fisheries and Ocean Sciences. The Port Valdez study resulted in numerous scientific publications, including three books, and provided research opportunities for more than 50 undergraduate and graduate students.
The project began as an investigation of the Port Valdez ecosystem prior to the construction of the Port Valdez marine oil terminal. The study is multidisciplinary, with Blanchard currently leading the biological component. An important part of the project includes looking at the potential effects on seafloor animals of wastewater and treated ballast water discharges at the terminal. David Shaw, professor emeritus at UAF, has been the leader of the hydrocarbon chemistry component of the project since 1976. Scientists say that effects on animals on intertidal beaches and the seafloor from wastewater discharged by the terminal have been minor.
The Port Valdez project is funded by Alyeska Pipeline Service Company.
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