Large floating mats of red algae continue to wash up on some parts of the coast choking out native plants and animal species. This week on the Down East Journal, we speak with North Carolina Coastal Reserve Research Biologist Byron Toothman about the impacts of this quickly-growing, invasive seaweed and how it’s altering our coastal ecosystem.
You may have heard about the algae that was recently discovered by Oregon State University researchers that tastes exactly like bacon when it’s fried. Well, the algae we’ll be talking about today is nothing like that. There are some types of algae taste good and are good for you, but others are toxic. Cyanobacteria, is blue-green algae, common in freshwater here in North Carolina. But in salt and brackish water, there’s another type of algae that’s harming the ecosystem and choking out native plant and animal species. North Carolina Coastal Reserve Research Biologist Byron Toothman is studying the seaweed called “Gracilariavermiculophylla.”
“We have lots of native red algae here but this particular one is an exotic that’s generally found in western parts of the Pacific, along the Asian coastline.”
There are many theories on how this invasive red algae ended up along the Carolina coast. It’s possible the seaweed was introduced when it became enmeshed in nets, lines and anchors on ships from Asia delivering goods to our ports.
“There’s evidence that several pathways could have brought it here. Some people thought it might have come with imported shellfish. And then there’s some evidence that it might have come along in the aquarium trade. People thought it might have been a nice seaweed to have in their aquarium or for some poly-culture activity.”
Despite its name, red algae is actually more of a dark burgundy to black color. Some even have a bluish green tint. It all depends on the availability of sunlight. Red algae can be found up and down the East Coast, from Maine to Florida. But in southeastern North Carolina, the “exotic gracilaria” is especially prolific in the Zeke’s Island basin and shallows around Masonboro Island, near Wilmington. Toothman says red algae is most commonly found in estuarine waters.
“It’s tolerant to a wide range of salinities but it’s happiest in an estuary where there could be a little bit lower energy in terms of water movement and plenty of salt, not too fresh, not too salty.”
Red algae is adaptive, thriving in summer heat and winter cold. Not only does it grow quickly, it spreads easily. Toothman says the persistence of this organism is taking its toll on our coastal ecosystem.
“It’s displacing some of the native species that we have. If you look out at some of the mud flats we have here in southeastern North Carolina, often times it will be the dominant algae that you see at any given point in time. And because there is so much of it, it can also be the cause of hypoxic conditions, or low dissolved oxygen.”
Toothman says there’s evidence of continuous hypoxic conditions around Zeke’s Island and Masonboro Island, especially during the summertime. These low levels of oxygen can drive fish and other animals out of the area.
“It’s also having an impact on some of the fishing community because there is so much of it and it fragments very easily so the drifting algae can pretty easily foul up commercial fishing gear and some recreational fishing gear it can be problematic for people trying to fish with nets and with lines.”
Red algae can also become entangled in small boat propellers and crab pots. Toothman is researching how a proliferation of the seaweed changes an ecosystem.
“The prevalence of the algae at a few sites changes the water chemistry such that I believe that there are some increases in the rates at which mercury can be converted into methylmercury form, which is what bio accumulates in our food supply.”
Red algae first showed up along the North Carolina coast 15 years ago, and in recent years has grown exponentially. Unfortunately, Toothman says there haven’t been any successful efforts to eradicate the algae.
“We’ve found a couple of uses for it. Some folks are using it for tertiary water quality polishing, cleaning up the nutrient portion of effluent from aquaculture facilities and some people are doing some work to try and find some natural products that are found within the algae.”
Researchers at the University of Porto in Portugal were successful in developing an edible film coating from red algae that can be used to preserve food.
