Green Clams: Assessing, Quantifying, and Promoting the Value of Ecosystems Services Provided by the Hard Clam Aquaculture Industry in Florida

Transcription

1 Green Clams: Assessing, Quantifying, and Promoting the Value of Ecosystems Services Provided by the Hard Clam Aquaculture Industry in Florida FINAL REPORT 1 July June 2015 FDACS Contract No Submitted to: DIVISION OF AQUACULTURE FLORIDA DEPARTMENT OF AGRICULTURE AND CONSUMER SERVICES Principal Investigator: Leslie N. Sturmer, Statewide Shellfish Aquaculture Extension Agent IV Cooperative Extension Service, Florida Sea Grant Cooperating Investigators: Shirley M. Baker, Associate Professor, School of Forestry and Resource Conservation, Fisheries and Aquatic Sciences Program, UF Kelly A. Grogan, Assistant Professor, Food and Resource Economics Department, UF Sherry L. Larkin, Professor, Food and Resource Economics Department, UF Submitted by: UNIVERSITY OF FLORIDA INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES July 31,

2 PROJECT RESULTS Attainment of Technical Objectives OBJECTIVE 1. Conduct Literature Reviews 1a. Compile an inventory of ecosystem services (ES) provided by shellfish, and clam farming in particular, especially those related to nitrogen extraction and carbon storage. In the first quarter, Dr. Baker s Lab (two PhD students, one undergrad student) met several times to discuss and work on Objectives 1 and 2. Individually, we conducted searches on Web of Knowledge and Google Scholar to find papers in both the primary and gray literature pertaining to ES by shellfish farming. Articles were uploaded to a shared Dropbox with categories of Nitrogen, Carbon, Filtration, and Ecosystem Services. In the second quarter, an individual was hired, starting in late-december, whose time was dedicated to this project. He conducted literature searches and loaded over 30 additional articles in the Dropbox. The Dropbox was shared with other investigators and their students, and the folder categories of Carbon Valuation and Nitrogen Valuation were added. In the third quarter, the Baker lab produced a rough draft of an extension-style document. This document describes the storage of nitrogen and carbon in clam shells and tissues, as well as the interactions of clams with the carbon and nitrogen in their environment and throughout their lifetime. In addition, the Baker lab drafted pertinent sections of a Clam Farm Environmental Benefits Calculator (see Obj. 4). In the fourth quarter, the Baker lab, along with the other investigators, completed an extensionstyle document with per-clam harvest of nitrogen and carbon calculated from completed laboratory measures (see Obj. 2). These data were also provided to complete the Clam Farm Environmental Benefits Calculator. Production of a time-lapse video, demonstrating the filtering impacts of clams on the environment, was completed and posted online with the Calculator. Baker collaborated with an artist to complete two figures illustrating the storage of carbon and nitrogen in a clam and interactions with the environment; these figures accompany the Calculator and are included in the extension-style document. 1b. Summarize the ES valuation literature associated with bivalve culture. Dr. Grogan and Dr. Larkin hired a graduate student to assist in the project. We conducted a thorough review of both peer-reviewed journal articles and posters, working papers, and dissertations pertaining to methods used to value ecosystem services provided by shellfish. Search engines included Google Scholar, ScienceDirect, and Springer Link. We divided this literature review into 3 parts: valuation of ecosystems; valuation of environmental services from shellfish (only one of these studies presents valuation of ecosystem services provided by clams), studies on carbon storage by timber rotation and nitrogen removal from wastewater; and a summary of nitrogen abatement costs from agricultural runoff. We constructed tables outlining 2

3 species, study area, ecosystem services valued, methods, and valuation per unit of service. These tables can be accessed via the Environmental Benefits topic page at OBJECTIVE 2. Identify and Address Ecosystem Services (ES) Information Gaps 2a. Identify key ES knowledge gaps in the literature, especially pertaining to nitrogen extraction and carbon storage. In the first quarter, available data from the Baker Lab and from the literature on clam oxygen consumption rates and filtration rates, as well as clam shell carbon and nitrogen content, were compiled. In the second quarter, we identified knowledge gaps. Upon examining the available data, we determined that information is adequate only for some clam sizes and temperatures. We determined that data is lacking, as follows: 1. Oxygen consumption rates (for calculating carbon mineralization rates, or CO2 eliminated) of smaller sized clams and at temperatures exceeding 25 C, 2. Filtration rates (for calculating nitrogen and carbon removal rates) at smaller sizes, 3. Nitrogen excretion rates at all sizes and temperatures, and 4. Carbon content of tissue and nitrogen content of both tissue and shell. 2b. Conduct pertinent laboratory measures to address information gaps identified in 2a. In the second quarter, an individual was hired in late December, to conduct needed laboratory measures. We adopted more accurate nitrogen excretion measurement procedures than those previously planned and arrangements were made with the Phlips lab to analyze water samples for nitrogen content, following clam incubations. Equipment for filtration rate measures was acquired. Arrangements were made with the Murie/Parkyn lab for use of freeze-drying equipment in preparing tissues for carbon and nitrogen analysis. Plans were made with personnel in Geological Sciences to conduct carbon and nitrogen analyses of tissues and additional shell material. In the third quarter, the employee was trained by a former student in the procedures required to conduct oxygen uptake measures. Oxygen uptake rate measures were conducted. Water samples for simultaneous nitrogen excretion rates were frozen and are awaiting analysis in the Phlips lab. Filtration rate measurement procedures were polished. Clam tissues and shells were freeze-dried and ground for nitrogen and carbon analyses. An efficient and inexpensive method of crushing shell to a fine powder was developed. In the fourth quarter, nitrogen analyses of water samples was completed in the LakeWatch Water Chemistry lab. Filtration rate measures were completed in the Baker lab. Nitrogen and carbon analyses of dried and ground tissue and shell were completed in Geological Sciences. Stable isotope mass spectrometry was used to determine the proportion of nitrogen and carbon in the samples. All transfers of samples and data were facilitated by the employee. From these data, total weight of nitrogen and carbon was calculated for each clam harvest size. Data was compiled for insertion in the extension document and Calculator. 3

4 OBJECTIVE 3. Determine the Feasible Range of Ecosystem Values In the third quarter, through review of the relevant literature, the feasible ranges of ecosystem values were identified for carbon sequestration and nitrogen removal. Additionally, the most appropriate values to be used in the online benefits calculator were identified. All relevant literature was summarized and documented. In the fourth quarter, the contribution of the Florida hard clam industry to the mitigation of nitrogen and carbon extraction was assessed. The costs that would be incurred to replace the industry s services with the next best alternative was calculated. For nitrogen removal, appropriate replacement cost values were based on the costs of wastewater treatment plants in various locations, including the cities of Clearwater and Fort Meyers in Florida. The clamproducing counties were then assigned either the value for Clearwater ($3.44 per pound of nitrogen removed) or Fort Meyers ($5.22 per pound of nitrogen removed), based on which location most closely matched the county s land values and cost of living, factors that affect the cost of wastewater treatment plants. For carbon sequestration, the creation and maintenance of pine tree plantations was used as a possible alternative to hard clam production. Costs included pine production, as well as the value of the land in an alternative use; in counties with high agricultural, commercial, or urban land values, this opportunity cost of utilizing the land as a pine plantation was high. The cost per metric ton of carbon sequestered was calculated for all clam-producing counties in Florida using previously reported estimates of these variable land use values. The cost included a weighted average of the opportunity cost of converting land to forest, where the weights were proportional to the amount of land in a county under crops, pasture, or range. The highest carbon sequestration values ($ per ton) were estimated for Collier County, while the lowest ($0.71 per ton) costs were in Franklin County, primarily due to lower land values in the more rural county. OBJECTIVE 4. Disseminate Research Results An extension-style report was developed by all investigators and accompanies this final quarterly report. A condensed version of the report is posted on the Online Resource Guide for Florida Shellfish Aquaculture website, This report will also be modified to fit the format required of an EDIS document, which will be made available through the UF Electronic Data Information Service (EDIS), a proven and well recognized extension publication system with over 7,000 documents. A Clam Farm Environmental Benefits Calculator was developed using values provided by Baker and Grogan. The Calculator is posted on the Online Resource Guide for Florida Shellfish Aquaculture website, The template is designed to allow a grower to enter his/her annual production and resulting nitrogen removal and carbon storage values are calculated (see Appendix I). In addition, economic values associated with the extraction of these nutrients are calculated for the individual s farm. 4

5 A website promoting Florida clams was developed and will be launched in August The vanity domain is In the fourth quarter, the site was redesigned based on feedback provided by various industry members. The home page features banner pictures, links to topic pages, an introduction to clam farming components, an infogram about the Florida clam industry, and featured videos (see Appendix II). The topic pages include information on the following: About the Industry, Environmental Benefits, About our Clams, Try Some! and Where to Buy. Two additional web pages, Calendar of Events and Clammunications, allow for updates and current information to be posted to the site. PROBLEMS ENCOUNTERED The programmer contracted to develop the Florida Clams website dealt with family issues this spring and progress on the website was halted, resulting in a delay of launching the site. PROJECT OUTCOMES AND IMPACTS In this study, the unique sustainability of the Florida hard clam aquaculture industry was assessed by examining three environmentally-beneficial ecosystem services (water filtration, nitrogen removal and carbon storage) provided by clam farming., Efforts focused on assembling ecosystem service measurements and values specific to bivalve culture, identifying information gaps for hard clams Mercenaria mercenaria, and translating information to Florida s hard clam culture industry. Measurements, particularly for harvest-sized clams at the water temperatures found in Florida, are not available through the literature. To address these information gaps, pertinent laboratory measures were determined and results are summarized in Table 1 and discussed below. Table 1. Water filtration, nitrogen removal, and carbon storage values determined per clam for three commercial size grades of Florida cultured hard clams. Water Filtration (gallons/day) Nitrogen Removed (grams) Carbon Stored (grams) Clam Grade Shell Width (mm) Shell Length (mm) Littleneck 25.7 (1.03 ) 46.9 (1.88 ) Button 22.9 (0.92 ) 41.7 (1.67 ) Pasta 20.1 (0.80 ) 37.2 (1.49 ) Water Filtration Rates of Hard Clams Shellfish filter phytoplankton (microscopic algae or plants) out of the water when feeding, thereby naturally cleaning and clarifying the water. The filtering rate of clams was measured in the lab using a fiber-optic colorimeter, which measures the turbidity of a phytoplankton solution. The turbidity of the water declined over time, as the clams removed the phytoplankton from the water. Using this data, the volume of seawater cleared of phytoplankton per day for three 5

6 commercial grades of hard clams was calculated; a littleneck-sized clam was found to filter 4.5 gallons of seawater per day (Table 1). Nitrogen Removal and Carbon Storage by Hard Clams The amounts of nitrogen and carbon removed from the ecosystem upon harvest were determined by measuring the contents of both clam tissues and shells. Clam tissues and shells were dried, weighed, and ground to fine powders. Stable isotope mass spectrometry was used to determine the proportion of nitrogen and carbon in the sample. From these data, the total weight of nitrogen and carbon in the tissue and shell of each clam was calculated (Table 1); each littleneck-sized clam represented about 0.09 grams of nitrogen and about 2.8 grams of carbon stored in tissue and shell. Valuation of Ecosystem Services provided by Clam Production in Florida Based on the results of the 2012 Florida aquaculture survey conducted by the U.S. Department of Agriculture, 25.4 thousand pounds of nitrogen were removed and thousand pounds of carbon were stored through the harvest of million clams statewide. The size of clams harvested was determined by surveying several shellfish wholesalers; it was assumed that 75% of the clams harvested were littlenecks or larger, 20% were buttons, and 5% were pastas. Thus, the economic value of these environmental benefits provided in 2012 was estimated at $99,680, which represents the public good value that the industry generates to Florida citizens at no cost. Results demonstrate the important contribution of hard clam culture to coastal ecosystem services. Findings on clam farm sustainability can benefit growers, wholesalers, and retailers by allowing them to inform buyers and consumers that shellfish aquaculture is benign and, in fact, provides ecosystem services. Consumers will benefit by being made aware of the environmental benefits of sustainable shellfish aquaculture. Estimates of nutrient reduction and carbon storage may, in the future, be adopted as usable or saleable nitrogen and carbon credits, further benefiting clam growers. NEW RESEARCH DIRECTIONS Benthic shellfish populations directly facilitate the movement of particulate organic matter from the water column into the sediments via suspension feeding and the biodeposition of pseudofeces and other wastes. This vertical transport is directly linked to benthic nitrogen cycling processes, including denitrification, which is an important mechanism for the removal of nitrogen from estuarine and coastal marine systems. Understanding the role that hard clam populations play in nitrogen cycling can provide the scientific basis for the continued development of sustainable culture practices. Dr. Baker and a graduate student will begin in 2016 to generate pilot data that can be used as the foundation for an expanded project that examines how Florida s hard clam aquaculture industry contributes to nitrogen cycling in estuarine and coastal marine ecosystems. 6

7 OUTREACH ACTIVITIES The Florida Clams website design and content outline has been presented to various industry representatives for their comments and review. One of the topic pages, About our Farms and Farmers, will feature the four regional growing areas (east coast, southwest FL, Big Bend, and Panhandle), thus highlighting the diversity of the state. Representatives from each growing area will be solicited in August to provide images and assist in the development of content. This ARC project provided funding to develop a framework for an industry-wide website. The site is intended to be functional beyond the life of this project to provide current information to buyers, consumers, and others. Since travel funds are not an allowable expense in the Florida Aquaculture Program, Sturmer will work with growers in other parts of the state during scheduled workshops or meetings to obtain feedback and gather additional information for the site. Further, the Cedar Key Aquaculture Association has agreed to provide funding beyond this project to maintain and update the website. 7

8 Appendix I. Florida Clam Farm Environmental Benefits Calculator posted to the website Online Resource Guide for Florida Shellfish Aquaculture, 8

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11 Appendix II. Home page of the Florida Clams website, 11

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