Saccharina latissima, or sugar kelp, is one of the dominant species in Maine’s kelp forests, providing
food, habitat, and clean water to support a rich marine ecosystem. It is also the bedrock of the state’s
burgeoning kelp aquaculture industry, which relies on the annual harvest of reproductive tissue from the
wild.
A new study led by researchers at Bigelow Laboratory for Ocean Sciences provides the most
comprehensive assessment to date of the genetic diversity and population structure of sugar kelp along
Maine’s coast. The team found moderate levels of diversity within each study site and identified four
distinct populations, shaped by the oceanography of a complex and dynamic coastline.
Previous work has shown that genetic diversity like this can bolster resilience to marine heat waves; it
also provides critical raw material for an aquaculture industry that is the largest of its kind in the country.
The findings, recently published in the Journal of Phycology , highlight the importance of regional
management strategies to protect and leverage this genetic resource.
“There’s clearly a wealth of genetic variation along the coast that needs to be considered in
management and restoration and that holds great potential for innovation in aquaculture,” said Senior
Research Scientist Doug Rasher, the study’s senior author.
Rasher’s team has published several studies showing how warming is driving the steady decline of
Maine’s kelp forests. This loss has cascading impacts on coastal ecosystems and is compromising the
wild resource that the aquaculture industry depends on. Responding to that loss requires understanding
the complex structure and potential genetic barriers of remaining kelp forests.
The team collected genetic material from sugar kelp at 11 sites spanning Maine’s “outer coast.” These
areas are far enough out to be subject to oceanographic forces that affect the whole coastline but close
enough to shore to be potential sites of industry sourcing in the future, the authors say.
They identified at least four distinct populations across study sites. The evidence suggests that genetic
mixing readily occurs between sites within each population, presumably driven by currents dispersing
kelp spores during their early life stage. However, kelp are mobile for only a very short window of time
before settling on the seafloor for most of their life cycle. Even with strong currents, spores seemingly
do not get very far, and there appears to be little gene transfer between populations.
“Having distinct populations means there are different genetic signatures along our coast, and some
populations could have individuals that are more or less suited to thrive in varied environments,” said
the study’s lead author, Rene Francolini, a former University of Maine PhD student in Rasher’s lab.
“That’s important for restoration work or when we think about farmers who might collect reproductive
tissue in one location and outplant seed in another.”
Earlier studies have asked these questions at both a larger scale, across all of New England, and a
very fine scale between adjacent bays. In contrast, this is the first study to focus on the Maine coast as
a holistic unit.
“We wanted to explore questions of genetic diversity within the state of Maine because that’s the spatial
scale that’s relevant to managing wild kelp forests, developing effective restoration programs, and
establishing best practices in aquaculture,” Rasher said. “We brought it down to the scale that really
matters from a management perspective.”
This study was made possible, in part, by the publication by another team last year of the first complete
sugar kelp genome. That resource enabled the researchers to map these genetically distinct
populations. It also made it possible to begin identifying specific genes unique to each population that
might help kelp forests adapt or be useful in an industry setting in the future.
“With a complete genome available, we can actually identify genes of interest and examine whether
any of these genes are uniquely expressed in a given population,” Francolini said. “We have yet to be
able to connect these genes to a specific function, but when we do, we will be able to pinpoint kelp
variants that are uniquely strong candidates for improving kelp conservation, restoration, and
aquaculture outcomes.”
This study was supported by the NSF Established Program to Stimulate Competitive Research (Grant
#OIA-1849227), the Louise H. & David S. Ingalls Foundation, Maine Sea Grant, and the Nature
Conservancy. Co-authors include Research Scientist Robin Sleith, as well as Kristina Cammen and
Damian Brady from the University of Maine.
Journal of Phycology
Observational study
Cells
Sugar kelp (Saccharina latissima) population genetics map onto geographic distance and oceanographic features across coastal Maine
15-Aug-2026