Sugar kelp along Maine’s coast has always looked, to the naked eye, like a single continuous ribbon of seaweed strung along more than 3,000 miles of shoreline. A new genetic survey says otherwise. Rene Francolini, who led the work as a PhD student at the University of Maine, along with senior author Doug Rasher and colleagues Robin Sleith, Kristina Cammen, and Damian Brady, collected genetic material from sugar kelp, Saccharina latissima, at eleven sites spanning Maine’s outer coast, then mapped the samples against the species’ recently published genome. The result, published August 15, 2026 in the Journal of Phycology, is a coastline that turns out to hold four genetically distinct sugar kelp populations, not one.
The team focused on outer-coast sites deliberately: places far enough offshore to feel the full force of Gulf of Maine currents and temperature swings, but close enough to shore that they matter for the state’s growing kelp aquaculture industry. What they found was a pattern shaped almost entirely by geography and water movement. Kelp spores don’t travel far on their own, so gene flow was common between kelp growing near each other within a population, but genetic exchange dropped off sharply between the four population clusters, each apparently kept separate by oceanographic features like currents and distance rather than by any obvious visible difference in the kelp itself.
That distinction matters more than it might sound like it should, because Maine’s sugar kelp is both a conservation concern and an economic one. The state’s kelp farms depend on sourcing healthy reproductive material, and restoration projects trying to rebuild kelp beds lost to warming water need to know whether kelp from one stretch of coast is a good genetic match for another. Rasher put it simply: “There’s clearly a wealth of genetic variation along the coast that needs to be considered in management and restoration.” In practice, that could mean choosing where to collect spores for a farm, or deciding which population is best suited to outplant in a restoration site with different conditions than where the parent kelp grew.
The next step, the researchers say, is figuring out what that genetic variation actually does. Right now the four populations are defined by their DNA, not by any confirmed functional trait, so a kelp variant with a genetic edge in warmer water or faster growth hasn’t yet been pinned down. Francolini frames that as the real payoff still to come: once specific genes are connected to specific functions, the same genetic map used to define these four populations could be used to identify which kelp is best equipped to survive a warming Gulf of Maine, and to breed or restore accordingly.