Charles Yarish is, by his own definition, a seaweed enthusiast. Over his 35-year career, the Stamford professor of ecology and evolutionary biology has followed his marine algae instincts around the world, studying seaweeds’ relationships, their physiology, and their interactions with the world around them.

Yarish’s most recent endeavor will use seaweeds to clean up pollution from human sources, as well as waste from fish and even people. This approach, dubbed extractive aquaculture or bioextraction, promises to use the physiological properties of seaweeds and other organisms to clean up excess nutrients in polluted areas, making them healthier, more productive, and more economically viable.

“Nutrient-enriched systems can contribute to harmful algal blooms, which deplete oxygen in the water,” says Yarish. “Shellfish and seaweeds can provide good ecosystem services by extracting organic and inorganic nutrients from seawater.”

Healthier aquaculture business

Integrated multi-trophic aquaculture (IMTA) is not a new idea: cultures in ancient Egypt and China used these natural techniques, says Yarish. By bringing animals and plants from different trophic levels – different levels on the food chain – into the same place, aquaculture can function more like a natural ecosystem.

Over the past year, Yarish and his colleagues received nearly $200,000 in funding from the Connecticut Sea Grant College Program and the NOAA Small Business Innovation Fund both to grow seaweeds for human consumption and to develop technologies that will support IMTA in New England coastal waters.

Yarish, who has studied seaweeds for many years, now hopes to use them to clean up water pollution.

Many types of seaweed need water rich in inorganic nutrients such as nitrogen and phosphorous to survive. “Fish poop,” says Yarish, is made up of just these nutrients, and so provides sustenance for the seaweeds. Human products that find their way into waterways, such as nutrients derived from sewage treatment facilities and from land runoff, also provide these nutrients.

To convince people to use seaweeds to clean up their waters, Yarish first wanted to make his techniques viable and available for small businesses. In February 2010, he and colleague Chris Neefus of the University of New Hampshire established a seaweed culture in his laboratory that could be used as a “seed bank” for aquaculturists to begin growing the seaweeds on their farms.

The researchers also worked with students and faculty at the Bridgeport Regional Aquaculture Science and Technology Education Center, a specialized high school that that introduces young people to the marine science and technology involved in aquaculture. Here, they created an open-source online resource detailing the specific techniques for cultivating seaweeds in aquaculture.

Their efforts have already started to pay off. The techniques have been used by Ocean Approved, a sea vegetable company from Portland, Me., which is working with Yarish and his graduate student Sarah Redmond to grow edible kelp (a type of seaweed) near Bangs Island, Maine.

Yarish is working with Ocean Approved to establish a kelp culture that grows on ropes suspended in the water column and attached to floats or raft systems from the company’s mussel farm. The company now harvests and sells its all-natural kelp to Whole Foods markets in New England.

“It’s a high-value, good-tasting, biosecure product,” says Yarish, referring to the lack of contaminants found in the kelp. Convincing people that they can not only clean up the nutrient enrichment in their waters but receive economic benefits in the form of a new product, he says, is key to the success of his program.