University of Alaska Fairbanks researchers have discovered a thriving ecosystem among the decomposing seaweed debris that covers many Alaska beaches, including nearly 100 different types of invertebrates found in surveys at a handful of sites on the Kenai Peninsula.

It’s the first Alaska-based survey of the marine algae that washes up on beaches, known as wrack, and comes at a time when global interest in the resource is booming. Wrack is being increasingly used for fertilizer and livestock feed, although harvests in Alaska remain limited.

Studies in the Lower 48, Europe and Australia have shown that wrack provides a unique and productive habitat, but no one had seriously examined it in Alaska before. 

“We didn’t just want to generalize what we know from other regions,” said Brian Ulaski, a postdoctoral fellow at UAF’s College of Fisheries and Ocean Sciences. “Things are a little different up here with seasonal light and temperature changes.”

Ulaski led the project, which was funded by Alaska Sea Grant, while pursuing his Ph.D. at UAF. The study was published in the May issue of Marine Environmental Research.

Researchers focused on a dozen sites around Kachemak Bay near Homer in summer 2021, collecting sediment cores using a clam gun. After sieving the sediment through a fine mesh screen, thousands of samples were bagged and returned to the Kasitsna Bay Laboratory for identification and counting.

Ulaski and a team of undergraduate and graduate students found about 47,000 tiny invertebrates among those specimens. With help from Derek Sikes, the curator of insects at the University of Alaska Museum of the North, they identified 87 different taxa among the collection, including tiny coastal centipedes and pseudoscorpions.

“It’s like a whole little ecosystem we didn’t know much about,” said CFOS professor Brenda Konar, who helped secure grant funding for the project.

Researchers also collected samples from beaches without wrack. The difference was striking, with far fewer specimens and less diversity. The bare beach samples consisted almost entirely of worms. 

The findings could be valuable for the Alaska Department of Fish and Game, which manages wrack use in the state but previously knew little about the resource. 

Relatively small amounts of wrack are being harvested in Alaska, with personal use capped by ADFG at two buckets per day. Three or four commercial harvest permits have been written annually in lower Cook Inlet in recent years. However, interest in collecting seaweed is clearly on the upswing, resource managers said.

“When you don’t know much about something, and there’s growing pressure to harvest it, obviously you want to know more,” said Ted Otis, a Homer-based ADFG research biologist. “Partnering with the university to do research in that area is a great match.”

University of Alaska-Fairbanks

  Alaska, debris, ecosystem, kachemak, microorganisms, seaweed, uaf