Seaweeds are consumed by many people living on or near the Salish Sea–from Indigenous peoples revitalizing the ancient foodways of their cultures to those simply seeking a readily available and highly nutritious protein source–but little is known about whether contaminants in the Sea’s waters could create health concerns for the people who eat it.
A new study, funded by the SeaDoc Society and led by researchers at Western Washington University, reports concentrations of up to 162 chemical contaminants in three species of edible seaweeds (bullwhip kelp, bladderwrack, and spiral bladderwrack) at 43 sites throughout the Salish Sea, both in United States and Canadian waters. Fortunately, most contaminants occurred at levels too low to be a concern for human health.
The study, whose lead author was WWU Research Associate Jennifer Hahn, was published in the scientific journal PLoS One.
A few toxic chemicals – arsenic, cadmium, mercury, PCBs, lead, and benzo[a]pyrene – were found in high enough concentrations that the study’s authors recommend people consume less than 5 grams of dried seaweed per person per day in sites known to be contaminated, such as Victoria Harbor. Five grams of dried seaweed is the equivalent of about one-and-a-half cups of freshly collected seaweed.
The research was led by Principal Investigator and WWU Fairhaven College Research Associate Jennifer Hahn, WWU Professor and Chair of the Department of Environmental Sciences Ruth Sofield, and WWU Marine Scientist Kathy Van Alstyne.
SeaDoc Society Science Director Joe Gaydos was a collaborator and co-author on the study.
“This was a great collaborative effort with the Tribes and First Nations,” said Joe Gaydos, SeaDoc Science Director. “Not only did Jenny Hahn worked directly with the tribes and First Nations to collect seaweed samples at their traditional harvest areas, she also went back to share findings with each Tribe and First Nation before the study was published in a scientific journal.”
Each year, the SeaDoc Society conducts a competitive grants program with the goal of supporting science where more information is needed and expected to directly improve the health of the Salish Sea ecosystem and its marine and coastal flora and fauna.
Of the 162 contaminants found in the samples, the one that worried the researchers the most were polychlorinated biphenyls, or PCBs. Banned for use in the U.S. since 1971, PCBs are extremely long-lasting compounds that were formerly used in electrical transformers and as a flame retardant. PCBs have been shown to be cancer-causing agents that “bioaccumulate” in the organisms that ingest them; the larger and more longer-lived the organism, the more PCBs it is able to store in its tissues which may cause harm to the organism. Once that organism – whether it is a fish, a seaweed, or shellfish -- is eaten by humans, the PCBs then begin bioaccumulating in its new host. High exposure to PCBs can cause cancer, birth defects, developmental delays, and liver changes.
Of the 43 sampling sites, some of the most heavily contaminated seaweeds were found near highly industrialized sites such as Victoria Harbor in B.C. and Waterman Point near Bremerton and Smith Cove near the Seattle Cruise Terminal.
The study was initially motivated by tribal members asking whether the seaweeds they were harvesting were safe to eat, said Hahn, the lead author of the paper and a recent graduate of WWU’s Department of Environmental Studies’ master’s-degree program. Hahn also did the majority of the sampling, often via her kayak or a small boat. WWU students helped process the samples and prepare them to be tested.
“These are traditional foods for many of the Coast Salish peoples,” said Hahn. “But given the highly industrialized nature of many parts of the Salish Sea, they correctly had concerns about pollutant levels in the foods that they had traditionally harvested for so long. That’s what got me started down this rabbit hole, knocking on doors and building relationships to put together a project that took more than six years to complete, and ended up with me sampling from Campbell River, B.C., all the way south to Olympia.”
Hahn, who has taught wild food harvesting and cooking workshops to local tribes and First Nations for more than a decade, said some of the sample sites were not easy to reach even by kayak, which given Hahn’s career as a wilderness guide who has solo kayaked from the Salish Sea to Alaska, is saying something.
“Some of those sample sites were pretty tough,” she said. “Between the currents and the weather, there were for sure times when I just couldn’t get out that day.”
Sofield said the study fills a niche in the vital understanding of an increasingly important local food source.
“This study was quite an effort - there aren't many studies that do cross-border sampling like this, and there is little understanding of seaweed contamination in the Salish Sea,” she said.
The studies’ co-authors include researchers from WWU’s Shannon Point Marine Center and Department of Environmental Sciences, the SeaDoc Society, the Washington State Department of Fish and Wildlife, the Washington State Department of Health, the NOAA Northwest Fisheries Science Center, and the University of California Davis Health and Food Safety Laboratory System. Funding for the study was provided by Western’s Border Policy Research Institute and the SeaDoc Society, a program of the Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California at Davis.
Photo by Florian Graner