Experiment To Test Environmental Benefit Of This Waquoit Weed

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By: Brent Runyon
Published: 04/20/12

Right now, red seaweed is growing in cylinders of nutrient-rich water at the Marine Biological Laboratory in Woods Hole.

In six weeks, Scott Lindell, manager of the Marine Resources Center and director of the Scientific Aquaculture Program, will place the native red seaweed near oyster cages in Waqouit Bay as part of an experiment to see how effectively the seaweed can remove nitrogen from the water.

It could turn out to be both a valuable tool for restoring the health of the coastal waters around Falmouth and an ingredient in a tasty salad.

“The whole premise of the project was, can we find effective ways of removing nitrogen from our coastal waters,” Mr. Lindell said.

The experiment is also designed to find out if the seaweed can be a viable crop to make into seaweed salad. “I’m hoping that farming seaweed, or sea vegetables, may have some food value,” he said. “We hope to have this on as many Fourth of July menus as possible.”

Mr. Lindell’s hypothesis is that growing shellfish and seaweed together can be a more profitable business model and help clean coastal estuaries more effectively than growing either crop alone.

While oyster aquaculture alone can be beneficial to local waters, Mr. Lindell said there is evidence that the seaweed enhances nitrogen removal. Harvesting aquacultured oysters removes twice the nitrogen if they are grown in conjunction with wild seaweed, Mr. Lindell said.

In the experiment, the native red seaweed, Gracilaria tikvahiae, will be grown on ropes suspended at different depths near oyster cages maintained by Washburn Island Oyster Farm in Waquoit Bay in about a half-acre area. Other oyster cages will be grown without seaweed.

Monthly measures of seaweed growth, oyster growth, and survival will continue through October. Mr. Lindell and his team will also sample oyster and seaweed tissue to measure the nitrogen content and estimate the nitrogen removed.

The initial amount of seaweed will be 15 kilograms, he said, but that should double every two to three weeks during the growing season between May and October when it grows particularly luxuriantly.

Gracilaria has historically been used in many food products for its gelling and thickening properties, Mr. Lindell said it may also be suitable for biofuels or as a fish feed supplement. He has personally eaten Gracilaria raw with sesame oil and sesame seeds and also cooked with other greens, like kale, and found both dishes to be delicious.

Because the species of seaweed is native to local waters, and the oyster farm is already in place, the Falmouth Conservation Commission said the experiment did not need its approval, Mr. Lindell said. The Massachusetts Department of Marine Fisheries granted Mr. Lindell a scientific permit for the project.

The project will cost $220,000 over two years, and is paid for with $155,000 through a Woods Hole Sea Grant, along with matching funds from MBL and the University of Connecticut.

Mr. Lindell came up with the idea two years ago while attending a conference focused on shellfish and seaweed aquaculture as a method for cleaning up degraded coastal waters. The approach, known as nutrient bioextraction, is the practice of farming and harvesting shellfish and seaweed for the purpose of removing nitrogen and other nutrients from natural water bodies.

At the conference, Mr. Lindell met Charles Yarish, a University of Connecticut professor whose research assesses the bioremediation role of seaweeds in Long Island Sound and other urbanized estuaries.

“Long Island Sound has an acute problem with algal blooms that can suffocate fish and shellfish,” Mr. Lindell said. “Charlie’s been actively looking at seaweed as part of their solution....I wanted to study bioextraction in total—what makes more sense, shellfish or seaweed? I came to the conclusion that they are not mutually exclusive and that growing seaweed is quite compatible with growing oysters.”

Last year, Mr. Lindell collected red seaweed from a dozen sites in Waquoit Bay and sent the samples to Dr. Yarish’s lab for DNA analysis for identification. From that material, Dr. Yarish started culturing two particularly fast-growing and robust native varieties of the target seaweed. Last week Dr. Yarish delivered twenty 3.5-gallon jars of seaweed to Mr. Lindell, who will continue cultivation under bright lights in bubbling nutrient-rich water in the Marine Resources Center until the seaweed is transplanted to the study sites next month.

Mr. Lindell and Dr.Yarish hope the potential applications for food, biofuel, and ecosystems services modeled by this project will inform business, policy, and community leaders of future options for managing natural resources.

“The Town of Falmouth is currently weighing its options for sewering, and is considering alternatives such as aquaculture and bioextractive technologies,” Mr. Lindell said. “The results of this project could help many towns on Cape Cod and elsewhere evaluate this potential method for improving water quality in our coastal ponds.”

While Mr. Lindell and his colleagues are conducting their experiments, the Falmouth Water Quality Management Committee will soon issue a request for proposals for its own shellfish aquaculture project in Little Pond. Mr. Lindell said he has been in touch with members of the shellfish subcommittee of the Water Quality Management Committee about his experiment, and he may submit a proposal to do the work, depending on the scope of the project.

The shellfish and seaweed project and the Water Quality Management Committee’s work could dovetail together, Mr. Lindell said, but it is too soon to tell. “This is not mutually exclusive. There are many complementary aspects,” Mr. Lindell said.

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