Mystery in the Mudflats: Marine Biology Expert Follows Invasive Seaweed Around the World

Mystery in the Mudflats: Marine Biology Expert Follows Invasive Seaweed Around the World

Invasive species

Sotka with the invasive seaweed in the fall 2014 issue of College of Charleston Magazine

From the time College of Charleston Associate Professor of Biology Erik Sotka visited coastal Oregon as a child, he was infatuated with the marine life he observed in tide pools.

“There was an enormous diversity of invertebrates and seaweed that I knew nothing about,” he remembered. “I always had an interest in being outdoors and I always loved science. It wasn’t until college that I realized I could combine those things and be in a marine lab.”

RELATED: Learn more about Sotka in this fall 2014 College of Charleston Magazine article

Sotka attended the University of Washington for his undergraduate degree and received his doctoral degree from the University of North Carolina: Chapel Hill. He did post-doctoral work at Harvard and Stanford Universities before coming to the College in 2005. When he arrived in Charleston, Sotka noticed a strange and extremely pervasive seaweed in the Lowcountry estuaries.

“The seaweed started showing up in South Carolina in 2002 and I arrived a few years later. Some people say that I brought it with me, but I promise I didn’t!” Sotka said. “I became interested in it with the same childlike notion that first got me interested in marine biology.” Local scientists didn’t know anything about the seaweed, so Sotka set out to solve the mystery in the mudflats.

It was clear to Sotka from early in his research that the seaweed, Gracilaria vermiculophylla (G. verm.) was an invasive species. “You can’t go onto a mudflat without seeing it.” What was unclear from the beginning was just how far his research on G. verm. would take Sotka, physically and figuratively. He and postdoctoral researcher Stacy A. Krueger-Hadfield, with the help of a National Science Foundation grant, will travel the world from Virginia to Japan, Delaware to France and beyond.

The seaweed, in addition to growing on “every latitude in the northern hemisphere,” exists between the lines in world history books – Sotka and Krueger-Hadfield’s working theory is that G. verm. spread after World War II when Japan sent oysters to Europe and the North American west coast as a peaceful gesture. The two believe that G. verm. unwittingly hitched a cross-continental ride inside the oysters. Planned summer 2015 travel to Japan and some European countries will bring the timeline of the seaweed’s great escape into focus.

RELATED: Read more about Sotka’s research here

Sotka and Krueger-Hadfield are working with Marine Biology Professor Allan Strand, a computer modeler, to better piece together the historical movements of G. verm.

Beyond tracking the origin of the seaweed, however, Sotka and Krueger-Hadfield will primarily work to determine what kind of effects G. verm. has on the ecosystems it invades.

“We can’t find tremendously negative effects right now,” Sotka said. “No animals eat it, but small crustaceans like to hide in it because it offers a protective structure. When it dies, however, it degrades very quickly and its nutrients fuel blooms of algae and bacteria that we don’t want in our estuaries.”

“We’re also nervous about hypoxia – that G. verm. could smother the mudflats after it dies and ‘mats’ on the flats,” Sotka continued. “Shrimpers hate it because it gets caught in their nets. We believe that’s one way it actually spread across the U.S. East Coast; in shrimping nets.”

And outside of its effects, Sotka is particularly interested in what genetic qualities allow the species to adapt so well to so many diverse climates. “We’re going to be bringing plants to our lab at the Grice Marine Lab, rearing them in isolation in the lab, and looking at various traits that they might have adapted; being resistant to herbivores and pathogens, being more tolerant to heat and cold stress.”

Thus far, Sotka has worked closely with undergraduate and graduate student researchers to develop and test theories about G. verm. “One student of mine who’s about to graduate discovered that it actually grows faster when it’s surrounded by more genetic diversity, than when in monoculture. This surprised us because these benefits of genetic diversity had never been documented for seaweeds before,” he explained.

While some of his questions are years away from being answered, Sotka’s research to date has filled in many of the blanks he encountered when he first came upon G. verm. With each experiment, the pieces of this puzzle come more readily together.

“I hope a year from now we have an idea of G. verm.’s genetic mechanisms of adaption,” Sotka said. “The ultimate goal is to help understand how to prevent more invasions. If we understand the evolutionary mechanisms, we might be able to create strategies to minimize future invasions.”