April 2012. MVSG secures funding with the Edey Foundation to investigate the potential of cultured seaweed in Lagoon Pond.
Preliminary Investigations into the Bioremediation
Potential of Cultured Seaweeds in Lagoon Pond
In recent decades, the water quality in the Island’s ponds has declined significantly and resulted in a damaged local marine ecosystem, compromised marine habitats and a decline in fish and shellfish populations. Recent results from studies conducted under the Massachusetts Estuaries Program ((MEP) in Lagoon pond confirm that the major cause for this environmental decline is nutrient enrichment in the form of excess nitrogen entering the ponds primarily from residential septic systems. The excess nitrogen causes microscopic and macroscopic algal blooms which in turn set in motion a cascade of damaging impacts including decreased dissolved oxygen, increased turbidity, loss of eelgrass, siltation and eventually stressed and dying fish and shellfish. In response to this recommendation, the Island community is searching for effective and affordable methods to reduce the excess levels of nitrogen in the ponds.
In this proposal, we seek to investigate the potential of seaweeds (macroalgae) to reduce nitrogen overloads in Island ponds. Solutions which seek to enlist the services of biological organisms are called bioremediation.
Martha’s Vineyard is not alone in its conundrum of finding affordable methods to reduce the nutrient pollution to its surface waters. A recent conference on Long Island highlighted the role bioextractive aquaculture can play in mitigating nutrient overloads. In theory this cutting edge technology proposes the use of aquatic plants and animals to extract unwanted nutrients from the surrounding environment. Nutrients targeted for removal are incorporated into their tissues as they grow. With the harvest of the cultured organisms, there is a net reduction in the offending nutrients. Ideally, the harvested cultured organisms also have value as food or industrial applications as fertilizer, biofuel etc. and, thus, the bioremediation becomes economically selfsustaining.
Cultured seaweed and shellfish both have the potential for bioextraction of nitrogen. They remove nitrogen at different stages in the nitrogen cycle. Seaweeds, like microalgae and other plants, are inorganic extractors. They remove nitrogen directly from the water column absorbing nitrogen in inorganic forms such as ammonia and nitrates. The algae use the nitrogen to create proteins and build their tissues. Shellfish exhibit a less direct route removing nitrogen via organic extraction. They do not consume nitrogen directly but rather remove it as the result of feeding on microscopic algae. Because of their more direct route of nitrogen removal, seaweed can be even more effective than shellfish as a bioremediation tool for removing nitrogen.
To date, shellfish aquaculture has been a more popular candidate than seaweed culture for bioremediation for primarily two reasons. First, shellfish culture is an existing established technology that can readily be applied for nitrogen bioextraction. Second, a key element of bioextraction is the removal of the bioextracting agent with its accumulated nitrogen from the environment. Because harvested shellfish are readily sold as a valuable food product, they readily fit the bill. Until quite recently, in the US both seaweed culture methods and markets have been limited.
Seaweed has been cultured for years in Asia where it has been a popular food item for centuries. Americans developed an appetite for fresh unadulterated seaweed in Asian cuisine including sushi and seaweed salads.
We propose to take advantage of these developments and attempt to experimentally culture several species of seaweeds on Martha’s Vineyard. Seaweed culture has the potential to improve Martha’s Vineyard waters while producing a new locally grown product that could also benefit the island’s economy. On the island where the local food movement is deeply anchored in the community, locally grown seaweed could find a place of choice in sustainable restaurants like the Home Port or State Road restaurant or in health food stores like Healthy Additions. If we can develop successful culture methods, local seaweed farms may someday join shellfish farms as a new local industry with the added benefits of bioremediation.
In this project we will investigate the feasibility of growing several local native species of seaweed: Gracilaria sp. and Aghardiella sp., two similar warm water red seaweeds for a summer harvest, and Laminaria saccharina, a cold water kelp for a winter harvest. With Gracilaria sp. and Aghardiella sp. we will experiment growing wild collected specimens vegetatively from cuttings. We will investigate growing sugar kelp on rope lines seeded with young sporophytes in a hatchery setting.
Gracilaria and Agardhiella:
· Wild specimens will be collected in the spring of 2012 with the help of Shellfish Constables and Katama oyster growers.
· The specimen size will be recorded prior to deployment.
· We will experiment with several grow-out methods including vertical longlines, horizontal long lines and bag culture.
· Lines will be deployed in Lagoon Pond, a high nitrogen pond in great need of bioremediation.
· Growth, survival and condition will be monitored to determine what method yields the best success.
· We will also monitor fouling which can impact the market value of edible seaweed product and experiment with fouling mitigation methods like fresh water dips, salt water dips or different line depth.
· We will also experiment with vegetative growth by cutting some of the wild
specimens in pieces and monitoring the rate at which they regenerate
· Samples of both species will be sent out to analyze nutrient content and nitrogen content to establish the value of the seaweed crop for food consumption or fertilizer and determine effectiveness in extracting nitrogen.
· Seeded lines will be purchased in the fall from Ocean Approved LLC., a Maine company which grows kelp commercially. Ocean Approved has already agreed to sell us seed lines at a discounted price and donate any technical support needed.
· The lines will be deployed in Lagoon Pond
· Growth will be monitored.
· Samples will be sent out to analyze nutrient content and nitrogen content to establish the value of the seaweed crop for food consumption and effectiveness in removing nitrogen.
· We will create and print a poster for the event Living Local in the fall of 2012 and will organize an informal seaweed salad tasting
· We will produce an educational video to be aired on MVTV
Lines will be deployed in Lagoon Pond, a high nitrogen pond in great need of bioremediation.
Amandine Surier, Rick Karney and the MVSG staff will design and conduct the seaweed experiments and growth trials with assistance from Oak Bluffs Shellfish Constable Dave Grunden and Tisbury Shellfish Constable Danielle Ewart. Paul Dobbins of Ocean Approved LLC has offered technical assistance with the culture of the sugar kelp.