Story behind the smelly red seaweed

Per­haps you saw the news the other day in the Boston Globe about a nasty red sea­weed washing up on the shores of Nahant, MA, where Northeastern’s Marine Sci­ence Center is located. The story quotes marine biology pro­fessor Matt Bracken, whose lab focuses on marine biodiversity.

I spoke with Bracken this after­noon to find out the story behind the story. Turns out it’s actu­ally long been in the making. Nearly two years ago, two North­eastern 3-​​Seas stu­dents, Christo­pher Marks and Natalie Low, were on a sci­en­tific research dive off the coast of Nahant when they ran into the unfa­miliar red sea­weed for the first time.

Their orig­inal mis­sion had been to map bio­di­ver­sity changes as they moved far­ther away from shore, but when they found this sus­pect organism, they knew it deserved its own atten­tion. Both stu­dents had studied with Bracken before and knew the envi­ron­ment, and its species, well. This stuff was not from around here.

Bracken and his stu­dents exhausted their guides and sci­en­tific keys with zero luck — they found nothing native to the area, or even near the area, that remotely resem­bled the new species. Don Cheney, an assis­tant pro­fessor of biology and a sea­weed spe­cialist based at MSC, took one look at the stuff and advised Bracken’s group to get in touch with Trinity Col­lege pro­fessor Craig Schneider, who had his own red sea­weed story to tell.

The pre­vious summer, Schneider hap­pened upon the unfa­miliar red sea­weed while enjoying his vaca­tion on the beaches of Rhode Island. I didn’t yet men­tion that this stuff appar­ently smells like rot­ting eggs when it dries out…some vacation.

When Bracken and Schneider com­pared notes, and genetic tests, it turned out they were indeed looking at the same stuff: Het­erosi­phonia japonica*.

As it’s name implies, H. Japonica actu­ally hails all the way from Japan, China and Korea — a rather dif­fi­cult journey for a little sea­weed plant, if you ask me. But this isn’t any old sea­weed. H. japonica is pro­lific: break off a piece and it will easily grow into two new plants. “Other sea­weeds can prop­a­gate veg­e­ta­tively like this,” said Bracken, “but this grows twice as fast as other species around here.”

In the 1980s H. japonica turned up in Europe and Bracken believes the most likely transit of the stuff to this con­ti­nent was from there via ship, as explained in the Globe article.

Inva­sive species that grow pro­lif­i­cally have a con­sid­er­able advan­tage over native species…they can out-​​compete the other guys for resources and could poten­tially have a dev­as­tating impact on the bio­di­ver­sity of the habitat. I asked Bracken why bio­di­ver­sity is so impor­tant, and he equated it to a well-​​run munic­i­pality, which has doc­tors, teachers, trash col­lec­tors, and a bunch of other people each with spe­cific role to help things run smoothly. It’s not that effi­cient to travel fifty miles to get to the doctor. Marine sys­tems with lower bio­di­ver­sity are also less effi­cient, said Bracken. Bio­di­ver­sity is linked to higher rates of func­tioning, effi­ciency and pro­duc­tivity, he said.

We’ve found that sys­tems with fewer native sea­weed species have lower bio­mass, are not as effec­tive at using nutri­ents, and there’s less mate­rial coming in from the base of the food chain to sup­port higher trophic levels,” he added.

While the pres­ence of the red sea­weed does cor­re­late with lower bio­di­ver­sity, they can’t yet say whether it’s causing the phe­nom­enon. “There are two pos­si­bil­i­ties,” said Bracken. “Either the inva­sive species causes the decline, or it invades where diver­sity is already nat­u­rally low.”

Sys­tems with lower diver­sity are less resilient against out­side intruders because they aren’t as effec­tive at occu­pying the avail­able space throughout the sea­sons. If native diver­sity is high, invaders are less successful.

Just this week, Bracken’s team began set­ting up exper­i­ments to find out which came first: the bio­di­ver­sity or h. japonica. They will sys­tem­at­i­cally remove the invader from a finite bit of the shore. If they find that native species start to regrow, this will indi­cate that the invader’s pres­ence is directly causing the low diver­sity. If the species don’t grow back, well…that would be another problem for another blog post.

If you’re on the coast, keep your eyes (and nose) out for the smelly red sea­weed. While the health depart­ment reports that bac­teria levels are normal in the areas where the sea­weed shows up, it may not be such a good thing for the rest of the species around here. It cur­rently extends from Northern Long Island Sound to Rock­port, MA.

*I’m slightly over­joyed to have dis­cov­ered the algae­base.