"GREEN" CLAMS: ESTIMATING THE VALUE OF ECOSYSTEM SERVICES GENERATED BY THE HARD CLAM CULTURE INDUSTRY IN FLORIDA, USA

Shellfish (oysters, clams, mussels) provide a favorable environment for the coastal waters in which they are grown. In turn, shellfish farming can provide local communities with a variety of ecosystem services, whose value can be quantified. To demonstrate the sustainability of hard clam aquaculture in Florida, three environmentally-beneficial ecosystem services (water filtration, nitrogen removal, and carbon storage) were examined. Efforts focused on assembling values specific to hard clam Mercenaria mercenaria culture. Measurements, particularly for harvest-sized clams at water temperatures found in Florida, are not available through the literature. To address these information gaps, laboratory measurements were obtained. The value of the contribution of the hard clam industry to nitrogen removal and carbon sequestration was assessed by calculating costs that would be incurred to replace the industry's ecosystem services with the next best alternative. For nitrogen removal, replacement values were based on the costs of wastewater treatment plants in Florida cities. For carbon sequestration, the costs of creating and maintaining pine tree plantations were used as a possible alternative to clam production.  

Using results from the 2012 Florida Aquaculture Survey, ecosystem services and their economic value provided by clam farming included: 1) 544 million gallons of seawater filtered from the statewide production of 136 million clams, 2) over 25 thousand pounds of nitrogen removed and 760 thousand pounds of carbon sequestered from the coastal environment, and 3) $99,680 in ecosystem benefits generated, which represents a public good provided to Florida citizens at no cost. Several deliverables, such as the Clam Farm Benefits Calculator, allow growers to inform buyers, consumers, and resource managers that shellfish aquaculture is a sustainable "green" industry. With inputs of farm location and number of clams harvested per year by grade size, the Calculator provides an estimate of the economic value of the benefits that a grower's crop provides on an annual basis (Figure 1). A website, FlaClams.com, promoting Florida clams was also developed. Results, presented as an infographics poster, illustrate these benefits, their value estimates, and how they relate to Florida's clam culture industry.