Coastal communities are increasingly recognizing the valuable ecosystem services provided by shellfish aquaculture. These services include, among others, improving water quality by removing excess nutrients. However, integrating the quantification of these benefits into the aquaculture permitting process can be challenging.
Scientists from the Northeast Fisheries Science Center and the National Centers for Coastal Ocean Science have created an online tool for oyster farmers in the northeastern United States. Aquaculturists can use it to obtain a science-based estimate of how much nitrogen their farms remove from local waterways.
The article published in the journal PLoS ONE presents an innovative online tool, the Aquaculture Nutrient Removal Calculator (ANRC), designed to bridge this gap.
A Multidimensional Environmental Service Provider
One of the most significant contributions of bivalve shellfish aquaculture is its ability to filter excess nutrients from the water. As bivalves feed, they remove nitrogen—a key pollutant that can lead to harmful algal blooms and oxygen depletion. This filtering process not only improves water clarity but also creates a healthier environment for other forms of marine life.
Beyond nutrient removal, bivalve farms also serve as habitat providers. The complex structures of aquaculture equipment can offer shelter and breeding zones for a variety of fish and invertebrates. This can lead to increased biodiversity and support the recovery of threatened species.
Additionally, bivalve aquaculture can contribute to coastal protection. Oyster reefs and other shellfish structures can help dissipate wave energy, reducing erosion and protecting shorelines.
Why Nitrogen Removal Matters
Nutrients like nitrogen are essential for life, but excess nutrients often end up in coastal waters from human sources, such as lawn fertilizers and agricultural runoff. When uncontrolled, algae can grow out of control. This can cause environmental problems, such as low dissolved oxygen levels, fish kills, and dead zones.
Oysters and other bivalves (mollusks with two shells) help keep nutrients in check by filter-feeding on algae. As they feed, these powerful shellfish improve water quality. This effect has been well-documented by scientists, although it is not typically considered within the aquaculture permitting review process.
The Science Behind the Tool
Scientific research has established the nitrogen-filtering capabilities of bivalve shellfish farms. As bivalves, such as eastern oysters, grow, they incorporate nitrogen into their tissues and shells. This nitrogen is subsequently removed from the environment when the shellfish are harvested.
Researchers at the National Oceanic and Atmospheric Administration (NOAA) compiled a comprehensive dataset on the nitrogen content and growth parameters of farmed oysters across the northeastern United States. They then adapted existing methods used by established nutrient management initiatives to quantify the amount of nitrogen removed through oyster harvest.
The analysis revealed minimal variation in nitrogen concentration within the dataset. Additionally, factors such as farm location, oyster ploidy (genetic composition), and farming practices (floating gear, bottom gear, or no gear) showed minimal impact on nitrogen removal efficiency. This finding enabled the development of a simple regression-based calculator applicable to a wide range of eastern oyster farms in the region.
‘We have heard from regulators and industry members that they need a simple and intuitive way to calculate the environmental benefits provided by shellfish aquaculture,’ said project leader Julie Rose. ‘We are excited to share our tool, which synthesizes data collected by excellent scientists across the region, to create a robust prediction of nitrogen removal that industry members and regulators can rely on.”
The Advantage of ANRC
The ANRC tool is designed to be user-friendly for both resource managers and shellfish growers. Here’s what it offers:
- Simple interface: Enter data on oyster size and harvest amounts to estimate the farm’s nitrogen removal capacity.
- Scientifically sound calculations: The tool is based on solid scientific data collected from the northeastern U.S. oyster industry.
- Permit integration: The ANRC generates a report summarizing the ecological benefits of nitrogen removal from the farm, specifically designed for integration with existing permitting review processes, such as those of the U.S. Army Corps of Engineers.
Streamlined Permitting with Ecological Benefits
The ANRC is a free online tool designed to simplify the process of quantifying nitrogen removal by oyster farms in the northeastern U.S., covering the geographic area from North Carolina to Maine. The tool requires basic user data, such as oyster size and harvest amounts, to predict the farm’s nitrogen removal capacity associated with harvesting.
But the benefits go beyond mere calculation. The ANRC generates a permit report in a specific format. This report provides a clear and concise overview of the ecological services associated with nutrient removal in areas experiencing nutrient pollution (eutrophication), along with project-specific data on nitrogen removal and references supporting the calculations. The report also includes:
- Farm location.
- Farming method (on-bottom, off-bottom, floating, or multi-methods).
- Ploidy (whether oysters have two or three sets of chromosomes).
- Harvest period.
In summary, by quantifying the environmental benefits of bivalve shellfish farms, the ANRC allows:
- Resource managers: To make informed decisions on aquaculture permits, considering both economic and ecological factors.
- Shellfish growers: To demonstrate the positive environmental impact of their operations, which could streamline the permitting process.
- Coastal communities: To enjoy cleaner waters and a healthier marine ecosystem.
Conclusion
By facilitating the quantification and communication of ecosystem services provided by shellfish farms, the ANRC aims to expedite the permitting process while recognizing the valuable role these sustainable aquaculture operations play in maintaining healthy coastal ecosystems.
The calculator was created to incorporate new data and information as they become available. The research team plans to add phosphorus removal to the calculator for a more comprehensive estimate of nutrient removal. They are also evaluating data availability to expand the nutrient calculator to the Gulf of Mexico.
The study was funded by the NOAA Fisheries Office of Aquaculture.
Contact
Julie M. Rose
NOAA National Marine Fisheries Service, Northeast Fisheries Science Center, Milford Laboratory
Milford, Connecticut, United States of America
Email: julie.rose@noaa.gov
Reference (open access)
Rose JM, Morse R, Schillaci C (2024) Development and application of an online tool to quantify nitrogen removal associated with harvest of cultivated eastern oysters. PLoS ONE 19(9): e0310062. https://doi.org/10.1371/journal.pone.0310062
