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Investigating the Mysterious Seaweed Die-Off - Hakai Institute

Investigating the Mysterious Seaweed Die-Off

Across the BC Coast, a collaborative team examines what caused a surprisingly poor seaweed harvest.

As the fog begins to clear, a kingfisher sings overhead and a group shares stories on its way back to the Calvert Island main lodge. Fanny Nelson, an elder from Metlakatla, British Columbia, strolled along the sandy shore and recounted experiences from her youth.

“I remember we used to go out in a skiff, to row just a short distance to the closest island to harvest [seaweed], now we have to use a speedboat and journey far away,” described Nelson.

Nelson, a member of the Coastal Guardian Watchmen in her community, spent the morning learning about a new seaweed monitoring effort that will hopefully shed light on the changes she has seen.

The oral history of coastal First Nations has stories about variability in the seaweed harvest through the years, but 2016 was different. During that spring and summer, very few black seaweed—known scientifically as Pyropia abbottiae [pie-ROW-pee-ah ah-BOT-ee]—could be found. Considered one of the more delicious seaweeds on the coast, the downturn was a loss of an important food source for many communities that some worried would not return and no one could explain.

A marine heatwave in the northeast Pacific is thought to have disrupted the life cycle of the black seaweed either directly by interrupting environmental cues or indirectly through nutrient limitation that affected multiple life stages. Diagram modified from Mitsunobu Kamiya by Jonathan Kellogg

So began a new collaborative effort to investigate the decline. For over a year, Jennifer Clark, a Hakai postdoctoral fellow at the University of British Columbia, and Hakai technician Lauran Liggan have been developing and testing a protocol to monitor algae growth and other environmental factors.

Their bimonthly observations at the Calvert Island Ecological Observatory record seasonal trends of the seaweed bloom and environmental characteristics to better understand how the conditions govern growth and signals the seaweed to progress to its next life stage. In addition, laboratory experiments and the monitoring efforts along the coast by the Coastal Guardian Watchmen will help Clark and Liggan tease apart the circumstances that led to the poor harvest in 2016.

“[I’m] quite sure that [Pyropia’s] purpose in life is to spread the love,” says Clark. She continues by describing how the seaweed’s physiology allows it to be rather prolific and its life cycle is precisely timed with nature’s cues. However, she thinks that environmental conditions in the lead-up to 2016 may have interrupted that progression.

By the summer of 2016 marine conditions were rather abnormal. A large marine heatwave—nicknamed “The Blob”—had altered conditions in the northeast Pacific for over two years. On top of that, 2015–2016 saw among the most intense El Niños on record. These anomalies manifested with sea surface temperatures along the coast that were two to four degrees Celsius warmer than normal over the prior winter.

Clark is testing two hypotheses about how warmer-than-normal waters could have influenced Pyropia. First, the microscopic stage of the seaweed, the conchocelis, may have failed to release spores due to the presence of warmer-than-average water interrupting the necessary environmental cue. If few spores released that would mean noticeably fewer seaweeds could develop, as was observed that summer. Alternatively, if the seaweed did not receive adequate nutrients due to the changes in coastal processes, multiple life stages of the seaweed may have been affected.

“I think the microscopic life stage [of the seaweed] was likely disrupted in 2015,” says Clark. “That has cascading effects on the next generation of seaweed and may echo in populations for many years.”

Back on the beach, the Coastal Guardian Watchmen are eager to help the scientists determine the cause. They want to do the survey correctly and ask questions like “Where do you put the quadrat?” and “How do you know where zero is?”

This attention to detail will be a great help to Clark and colleagues who are still trying to understand specifics about where Pyropia prefers to grow. Part of their research is investigating where the microscopic life stages are found in the intertidal zone.

“We know that the microscopic stage, called the conchocelis, bores into calcium carbonate materials, like barnacles or shells,” notes Clark. “But, we don’t know what specifically happens in the life cycle between late summer and early spring.”

Richard Reid, a fisheries technician from Bella Bella, offers his observation, “There’s always one blade and one barnacle growing on my outboard motor!”

“Ahh, a strong positive relationship!” answers Margot Hessing-Lewis, a nearshore marine ecologist with the Hakai Institute. Everyone starts to chuckle.

With feedback from participating First Nations, the scientists hope to refine the protocol and make Pyropia an indicator species in the ongoing marine planning along the coast. Through the collaboration, everyone hopes for a future where harvests may be forecast in a way that communities could adapt to a poor year; a possibility that has everyone feeling optimistic.