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Mote to Make Fish Farming Greener Using Saltwater Plants

December 9th, 2010


Mote Aquaculture Research Park
Mote Marine Laboratory
Mote to make fish farming greener using saltwater plants

Mote’s earth-friendly fish farm is about to get even greener — a large-scale project is getting under way this week that will begin using solid fish waste to grow saltwater plants for restoration projects.
The project is designed to be a model of how saltwater fish farms can cost-effectively recycle all of their waste — a goal commercial-scale aquaculture has yet to achieve. The move is a key step forward for sustainable aquaculture at Mote.

The project builds on Mote’s longstanding efforts at Mote Aquaculture Research Park (MAP), which raises saltwater fish more than 17 miles inland using 100-percent recirculated water. This process releases no waste into the oceans, but until now has produced some dry solid waste that had to be disposed of on land.

Growing plants to clean water from aquaculture is a centuries-old technique. In fact, Mote has been growing wetland plants at MAP since 2006. But the water used to grow those plants comes from Mote’s freshwater sturgeon production facility.

Since Mote’s saltwater systems re-use 100 percent of the aquaculture water from snook and pompano studies, there is no water discharged. Instead, in this expanded program, Mote will use the solids.
By using this waste to feed saltwater plants – and doing it on a large enough scale to translate to commercial operations – this innovative system could serve as a model for sustainable marine aquaculture efforts across the nation and beyond.

“For years, Mote has developed recirculating aquaculture technology to reduce the environmental impact of producing seafood – but there’s still is an impact if you can’t use the solid waste,” said Dr. Kevan Main, Director of Mote’s Center for Aquaculture Research and Development and leader of the project. “When I show people around Mote’s facility and point out that the saltwater is completely recirculated, some observant person will ask, ‘Where do the solids go?’ Now we’ll be using them up to grow plants for coastal environments.”

The project, led by Mote scientists and funded through the National Oceanic and Atmospheric Administration’s Sea Grant program, is part of a 2-year study with partners from Aquatic Plants of Florida, Inc., a Sarasota business that grows plants for environmental restoration, the University of South Florida, Auburn University in Alabama and Aqua Green a private aquaculture company in Mississippi.

“Totally closed saltwater systems have been examined on an experimental basis, but to our knowledge they haven’t been done at this scale,” Main said. “We have a full production unit capable of producing 40,000 fingerling [juvenile] fish and their waste will feed nearly 110,000 plants.”

The waste will come from facilities used to grow Florida pompano, a popular sport fish that is currently bred, hatched and raised at MAP.

The pompano waste will feed two large tanks in a greenhouse stocked with three plant species: black needle rush, red mangrove and smooth cordgrass. All three are commonly used by local, state and federal governments to restore coastal environments after impacts such as hurricanes, oil spills and other environmental disasters.

Another part of this project, led by Auburn University and Aqua Green, will involve recycling pompano waste in a different process and using it to grow three types of algae that produce agar and carageenan — substances used as food additives, including in many products on grocery store shelves.

The plants from Mote will be sold for environmental restoration projects by staff at Aquatic Plants of Florida, who started producing and distributing freshwater plants through a research partnership with Mote in 2006.

The plants will be grown mainly for Florida restoration projects, but some smooth cordgrass will be stock from Louisiana. That cordgrass could, in time, be used to mitigate damages from the Deepwater Horizon oil spill, if cordgrass harmed by the spill does not rebound on its own. Cordgrass is a major component of estuaries, providing habitats for coastal and marine wildlife and, in the case of the spill, it also kept oil from reaching many plant species closer to dry land.

For the current project, the partners aim to produce one crop of saltwater plants in spring 2011 and another in summer. “The species of plants we’re using and the way we’re growing them is designed to fit with restoration projects,” said Gil Sharell, founder and president of Aquatic Plants of Florida. “We’ve already had success with producing freshwater plants at Mote for restoration. It seems like natural progression to go from fresh to salt.”

Scientists at USF and Mote will evaluate how efficiently the plants take up nitrogen and phosphorous, chemicals in the fish waste that plants need to grow.

Project partners will evaluate the costs and benefits of this new system for producing pompano as well as beneficial plants, to compare the economics of this system with current industry practices.

Hayley Rutger
Public Relations Specialist
Mote Marine Laboratory / Mote Aquarium
(941) 388-4441, Ext. 365
hrutger@mote.org