One of the most common selling points for kelp farming is that the long lines of seaweed double as habitat, a sort of seasonal forest that fish and invertebrates can move into. A team at NOAA Fisheries’ Alaska Fisheries Science Center decided to test that claim in Southeast Alaska, where kelp aquaculture is a young but growing industry. Led by macroalgae and mariculture research biologist Jordan Hollarsmith, with co-authors Rebecca Cates, Leah Valdes, Lia Domke, Kimberly Ledger, Diana Baetscher, Alicia Bishop and Skylar Bayer, the study was published this summer in Annals of Botany. NOAA released its write-up in mid-September. The answer was mostly no, but not in a way that should worry kelp farmers.
The work took place at two commercial farms run by Sea Quester Farms, 10-acre and 25-acre sites west of Juneau growing native bull kelp, split kelp and sugar kelp. Kelp farms in Alaska are seasonal: lines are seeded in fall, put out on the water in winter and harvested in spring or early summer. That means any habitat they offer comes and goes with the crop. To see whether it made a difference, the researchers paired each farm with a nearby control site with similar conditions but no farm gear, then surveyed all four sites over the course of a year. Divers on scuba counted invertebrates and described the seafloor. Fish were identified through environmental DNA, the traces of genetic material animals shed into the water, which lets scientists detect species without catching or seeing them. The team also measured nutrients, temperature and salinity.
What shaped the fish community most was the time of year, which explained about 30 percent of the variation, followed by depth. For invertebrates, the biggest factor was which part of the area a site was in. Water conditions changed with season and depth, but not between farm and non-farm sites. The researchers found no group of species unique to the farms. In their words, the farms did not appear to offer “novel habitat-provisioning services,” but they also “did not appear to detract from the important habitat already present.” Hollarsmith put it more simply in NOAA’s announcement: “Our findings show that at these sites, kelp farms did not change what species we observed in each location.”
There’s an important caveat in the paper itself. Because one sampling event was missed, the team couldn’t calculate whether the farm effect was statistically significant. The farm/no-farm difference accounted for about 4 percent of the variation in fish communities and about 22 percent for invertebrates. The authors think the invertebrate number more likely reflects patchy seafloor communities than a response to the farms, but that’s an interpretation, not a settled result. This was also two small farms, over one year, in one region. NOAA notes that future work should look at whether farm size, local conditions and harvest methods change the picture.
For regulators deciding how to permit a growing industry, a “neutral” result is useful in its own right. It suggests that, at this scale, kelp farms can share the water with what’s already there. It also means the habitat argument for kelp farming isn’t something to take for granted, which fits the more sober recent look at kelp farming’s economics in Massachusetts.
Further reading: Hollarsmith, J.A. et al., “Assessing the potential fish and macroinvertebrate habitat-provisioning services of kelp aquaculture in Southeast Alaska,” Annals of Botany (2026); NOAA Fisheries, “Kelp Farms and Marine Life Co-Exist in Southeast Alaska” (2026).