Photo above: Salmon smolts in a tank at Sitka Sound Science Center at Sitka, Alaska.
A new study under way this week at the Sitka Sound Science Center in Sitka, Alaska, is investigating how crude oil and dispersant affect hatchery-reared coho salmon to test for subtle or delayed health impacts that are normally challenging to document when oil spills occur.
The study, led by Mote Marine Laboratory scientists from Sarasota, Fla., in partnership with the Sitka Sound Science Center in Alaska, is part of Mote’s long-term effort to conduct controlled lab testing for “sublethal” impacts of oil and dispersant on many marine species. Sublethal impacts (sometimes called “delayed mortality”) will not kill animals outright, but may subtly affect their health or reproductive capabilities in ways that could ultimately affect their survival and population status.
Roger Vallion, staff member at Sitka Sound Science Center, and Mote Marine Laboratory senior scientists Dr. John Reynolds and Dr. Dana Wetzel gather around their lab experiment to study oil and dispersant effects on coho salmon on Sept. 30 in Sitka, Alaska.
(Credit Mote Marine Lab)
Sublethal impacts have been difficult to predict and document in catastrophes like the Exxon-Valdez and Deepwater Horizon oil spills. There is limited knowledge about health implications from exposure to the oil and dispersant for various species, making predictions about impacts, and more importantly protection and restoration efforts, difficult. Documenting only immediate mortalities will not reveal how animals’ reproduction, immune responses and genetic code (DNA, the “blueprint” for life) might be impaired in animals exposed to oil or dispersant. Without a comprehensive approach to environmental damage assessments, including studies of sublethal impacts, resource managers may underestimate the likelihood of post-spill sustainability of impacted species, and thereby underestimate outcomes important to ecosystem health, commercial activity and subsistence communities.
Coho salmon are important to subsistence, commercial and recreational fisheries, and the U.S. catch for this species was estimated to be worth $28 million in 2012, according to the National Oceanic and Atmospheric Administration. Most of the U.S. catch comes from Alaska. These salmon have declined in number over the years due to multiple human activities that have led to habitat loss and changes in water quality. Some populations are listed as endangered or threatened under the U.S. Endangered Species Act. The species is not currently listed in Alaska, but these fish are among the many species considered vulnerable to oil spills in Alaska and beyond. A key question is: Exactly how vulnerable?
The current exposure component of the study, which started on Sept. 28, 2015, and will continue through early in 2016, is using controlled lab experiments with coho salmon to try to characterize some cause-and-effect relationships between salmon health and known exposures to North Slope crude oil and Corexit 9500 oil dispersant. Salmon health assessments in this study will evaluate changes to the immune system, cell damage, reproductive system impacts and changes in lipid levels. Such evaluations will take place immediately after the salmon are exposed to specific concentrations, and will be repeated in several months to assess delayed impacts.
The study is led by Mote senior scientist Dr. Dana Wetzel and co-primary investigator Mote senior scientist Dr. John Reynolds. Research is being conducted at the Sitka Sound Science Center, which is dedicated to increasing understanding and awareness of terrestrial and aquatic ecosystems of Alaska through education and research. The facilities and expertise at the Center include salmon rearing and release through a hatchery operation.
Mote’s long-term research plan is to carry out additional oil/dispersant sublethal exposures with key Arctic organisms and to inform key stakeholder groups such as wildlife managers, other researchers and Alaskan communities, of the results. Learning more about the consequences of oil and dispersant exposures on Alaskan species will help to prepare for future oil exploration, drilling and shipping in order to best preserve natural resources.
Funding for the current project is provided to Mote Marine Laboratory by the North Slope Borough as part of the North Slope Borough/Shell Baseline Studies Program, which operates a steering committee of independent scientists and representatives from municipalities, native villages and Shell. Funding for the Mote Marine Laboratory study is also provided by the Prince William Sound Oil Spill Recovery Institute.