Current Research at Milford Laboratory
Our Milford staff develops probiotics for use in oyster hatcheries and performs studies in aquaculture gear as habitat for marine life, nutrient bioextraction studies, shellfish genetics research, offshore shellfish aquaculture potential, and responses of shellfish to ocean acidification.
NOAA Fisheries' primary mandates are to use sound science to manage and conserve the nation's ocean resources and habitats, and to ensure their renewability for the future. Although our techniques have advanced over the years, the Milford Laboratory has always made strong positive contributions to meeting these objectives.
Present research at the Milford Laboratory emphasizes shellfish aquaculture and ecosystem-related work. Our well-integrated aquaculture research program evaluates current and proposed marine aquaculture practices for technical effectiveness, environmental compatibility, and sustained commercial success. Working closely with industry partners, we provide shellfish aquaculture science and develop new methods and technologies to enhance production. In addition, we study the interactions between aquaculture practices and coastal marine habitats and species. Our research supports the sustainable expansion of domestic aquaculture.
Our scientists are trained in a wide variety of disciplines, including chemistry, ecology, physiology, biochemistry, genetics, immunology, bacteriology, algology, and pathology. The versatility of both the facility and our staff at the Milford Laboratory make this unique blend of research possible.
Probiotic Bacteria for Use in Shellfish Hatcheries
Hatchery production of bivalve shellfish seed for commercial grow-out or restoration can be constrained by bacteriosis in tank-cultured larval stages. Environmentally-friendly methods for controlling microbial pathogenesis with probiotic bacteria are becoming increasingly preferred over repeated use of antibiotics, which can select for resistant pathogens in the environment. Research at the Milford Laboratory has identified a Vibrio sp. bacterium (OY15), isolated from Eastern oysters, that significantly improves survival of larval oysters (Crassostrea virginica) challenged with a Vibrio sp. shellfish-larval pathogen (B183). Possible mechanisms of OY15’s probiotic effect appear to be stimulation of immune function. Studies to confirm that probiotic bacteria generally are effective because of immune-stimulation have been completed using gene-expression analysis to demonstrate regulation of certain immune genes in larvae following treatment with OY15. Based upon these results, we have developed a functionally-based screening protocol for testing of probiotic candidates employing these in vitro immune-function assays using hemocytes from adult bivalves. Molluscan shellfish hatcheries across the U.S. will benefit from eventual availability of probiotic bacteria as a component of “functional feeds,” to increase seed production, and will contribute directly to the objectives of the NOAA Shellfish Initiative.
In efforts to commercialize probiotic strain OY15 as a safe, stable and cost-effective product for the commercial oyster aquaculture industry, the Milford Laboratory, with guidance from NOAA’s Technology Partnerships Office, has advanced work on oyster probiotics by negotiating partnerships with private industry through a Cooperative Research and Development Agreement (CRADA) and several Material Transfer Agreements.
In September 2016, Diane Kapareiko, Gary Wikfors and Dorothy Jeffress (Ecosystems and Aquaculture Division, Aquaculture Sustainability Branch) were awarded the Department of Commerce Silver Medal in recognition of developing the environmentally-friendly and safe probiotic bacterial strain OY15 which prevents bacteriosis and improves survival of oyster larvae, as well as negotiating a Cooperative Research and Development Agreement with private industry to advance commercialization.
A major focus of the Genetics research program is to investigate the application of genetics and breeding technology for improving growth and survival of economically and ecologically valuable shellfish, which have declined, such as bay scallops. Results could contribute to increased commercial production, recreational harvesting, and reduced imports. Three major approaches are being explored for culture, enhancement and restoration: breeding, population or molecular genetics, and field evaluations. Responses to selective breeding, inbreeding and hybridization are being determined by developing lines for increased growth and survival, with positive results previously with oysters and currently with scallops. In addition, genetic diversity of various stocks and populations is being ascertained with molecular technology to support or complement breeding and broodstock management. Molecular (e.g., DNA) analyses are investigated for genotypic markers and expression in stock identification, with innovative biotechnology methods applicable to other shellfish species and different marine organisms from bacteria to fish. Habitat and environmental suitability and field performance evaluations also are being conducted with phenotypic markers such as striped shells credited to us. Observations are made on differences in growth and survival of shellfish under various conditions, comprising laboratory and field components. There are collaboration, outreach, resource and technology transfer activities.
For more information, contact Sheila Stiles.
Shellfish Immune Status
Hemocytes, essentially blood cells, in bivalves such as oysters, clams, scallops, and mussels, are responsible for various physiological functions including immune defense, nutrition, and waste disposal. By understanding the functions and responses of these cells to environmental conditions, we are able to gain insight into the ability of hemocytes to maintain health when exposed to environmental stresses. We are able to achieve this understanding with the use of physiological probes, coupled with microscopy and flow cytometric applications in both laboratory and field settings. Eastern oysters, northern quahogs, bay scallops, blue mussels, and soft-shell clams, all species of economic or ecological importance in coastal habitats, are being studied. Ultimately, an improved understanding of the effects of changing environmental conditions on the health of farmed and wild-harvest shellfish will aid in local and national decision making.
For more information, contact Gary Wikfors.
Aquaculture and Environmental Interactions
Improving Phytoplankton Quantification Methods
Phytoplankton are photosynthetic microscopic algae at the base of marine food webs. Shellfish feed on phytoplankton directly. Phytoplankton biomass and productivity are key factors in coastal processes that are important in selecting shellfish aquaculture sites and quantifying interactions between shellfish aquaculture and the environment. Red fluorescence of chlorophyll a when phytoplankton samples are illuminated with blue light (referred to as ‘in vivo fluorescence’) is used widely to estimate phytoplankton biomass, hence food availability for shellfish. Reactions of chlorophyll to light, such as non-photochemical quenching during the day, and circadian rhythms of phytoplankton influence chlorophyll fluorescence yield, compromising the accuracy of chlorophyll measurements from in vivo fluorescence. Current research is evaluating ways to correct in vivo fluorescence measurements to yield more accurate chlorophyll estimates in environmental and culture-system samples.
Research is also ongoing developing measurements of phytoplankton/primary productivity with variable fluorescence techniques. The results will be useful in quantifying carrying capacity of a specific site. We are also collaborating with EPA and CT Department of Energy and Environmental Protection in aiming at using the information for the water quality management of the Long Island Sound.
For more information, contact Judy Li.
Shellfish feed by filtering plankton and other organic material out of their local environment. They assimilate the nitrogen and phosphorus contained in this organic material into their tissues and shell as they grow. In eutrophic coastal areas that have excess nutrients and an overabundance of phytoplankton, shellfish filter feeding can improve water quality. A recent two-year collaborative study quantified the nutrient assimilation benefits provided by ribbed mussels grown on a commercial mussel raft in the South Bronx, New York.
A recent collaborative project between NOAA National Centers for Coastal Ocean Science, the Milford Lab, the US Environmental Protection Agency, and a variety of other partners modeled the nitrogen removal from Long Island Sound and Great Bay, New Hampshire, provided by the local oyster aquaculture industries and calculated the dollar value to replace this ecosystem service with traditional nutrient reduction approaches.
The Milford Lab is currently working on three research projects that seek to document the nutrient removal services provided by shellfish:
- measuring and modeling nitrogen removal provided by hard clams and eastern oysters to the Town of Greenwich, Connecticut, and valuing the water quality benefits conferred to the town by the local shellfish population;
- comparing the nitrogen and phosphorus content of diploid and triploid oysters (oysters with two and three sets of chromosomes) over the growing season in the Chesapeake Bay in partnership with two shellfish growers, the Oyster Recovery Partnership, and the Virginia Institute of Marine Science;
- quantifying nitrogen removal by ribbed mussels and seed oysters in the lower Providence River, Rhode Island.
Check out the NOAA Fisheries feature story.
Oyster Cages as Finfish Habitat
Milford Lab staff are using GoPro cameras to document habitat services provided by aquaculture gear to fish in Long Island Sound. Off-bottom oyster cages are an increasingly common method for culturing oysters. These cages are complex three dimensional structures that may provide habitat for fish and other animals. Shellfish growers routinely observe fish of various life stages interacting with aquaculture gear on their farms. Oyster farms with large numbers of cages may act as artificial reefs, attracting a variety of fish species.
Researchers at Milford are conducting a series of field trials to:
- Understand how fish interactions with oyster cages compare with fish activity at natural habitats such as a rock reef.
- Analyze how oyster cage density influences fish abundance and behavior.
- Determine whether different styles of oyster aquaculture cages provide different habitat services to the local fish community.
To record video of fish activity in and around oyster cages, we equipped the cages with GoPro cameras. We also collected video on natural rock reef habitats for comparison.
We have collected over 1,000 hours of underwater video and analyzed it for fish abundance and community composition. To date, we've observed 20 species of fish associating and interacting with oyster cages. Preliminary observations of fish behavior suggest that fish use oyster cages in a variety of ways, including foraging, station keeping, and during courtship. We are working with regulators and fishery managers who make decisions about sites for shellfish farms and protecting habitat for recreationally and commercially important fish species. Our data will help inform their decision-making process.
Ocean Acidification / Climate Change
About a quarter of the carbon dioxide released into the atmosphere is absorbed by the ocean. This causes changes to water chemistry (such as pH) that may impact marine life. Current research focuses on how ocean acidification may affect economically-important bivalve species including: eastern oysters, blue mussels, bay scallops, surfclams, and sea scallops.
Scientists at the Milford Lab are partnering with Rutgers University and Massachusetts Maritime Academy to conduct experiments measuring feeding, excretion, and respiration of eastern oysters, surfclams, and Atlantic sea scallops in differing pH scenarios. Pousee et al (2020) recently described the physiological response of surfclams to decreased pH. We will use these data in models to better understand metabolism and growth responses for each of these species under different environmental conditions. This project is expected to yield insight into how aquaculture and wild fisheries' performance may be impacted by changing ocean chemistry.
Milford Lab researchers are also partnering with scientists and students from Stony Brook University to determine whether blue mussels and bay scallops can overcome the effects of ocean acidification through acclimation and/or adaptation. Research focuses on investigating whether bivalves can adapt to ocean acidification conditions across multiple generations, and whether tradeoffs to growth and development occur when grown in lower pH conditions.
For more information, contact Shannon Meseck.
NOAA Fisheries Feature Stories: