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
Bacterial disease can be a major cause of death among shellfish larvae in commercial hatcheries. In the United States, hatcheries do not use antibiotics to control these diseases. While some bacteria can cause lethal disease, other strains of bacteria can actually protect larvae from it, improving hatchery production and reducing costs. These “good” bacteria are called “probiotics,” the Latin for “promote life.”
The Milford Lab discovered and developed a probiotic bacterial strain labeled OY15, a benign strain of Vibrio alginolyticus isolated from the digestive glands of oysters, as an environmentally-friendly way to manage bacterial shellfish pathogens in hatcheries. This naturally-occurring bacterium provides disease resistance to Eastern oyster larvae, improving survival by 20 to 35 percent when challenged with the known larval shellfish pathogen Vibrio corallilyticus. Our research confirmed that probiotic strain OY15 works by stimulating the defense abilities of oyster hemocytes (similar to white blood cells) to respond to and eliminate harmful bacteria.
The Milford Lab is collaborating with public and private industry partners to commercialize OY15 for use as a feed supplement in commercial hatcheries. Prospective Research, a private biotech firm in Massachusetts, has manufactured a freeze-dried powder formulation of OY15, and provided it to the Milford Lab. With funding from the NOAA Office of Aquaculture, we have successfully beta-tested this new formulation of OY15 on Eastern oyster larvae in collaboration with public and private shellfish production hatcheries.
Preliminary data from a trial on Pacific oyster larvae performed at Hawaiian Shellfish Oyster Hatchery suggest that growth and performance of OY15-treated larvae were markedly better than for larvae not treated with OY15. To confirm OY15’s probiotic effects on Pacific oyster larvae, three commercial Pacific oyster hatcheries will perform hatchery-scale trials during the 2021 season—two in the U.S. Pacific Northwest and one in Ireland.
If we confirm that OY15 effectively improves performance and survival of two different species of oyster larvae in hatchery-scale trials, that may be an indication that the benefits of OY15 are more widely applicable. Success with Pacific oysters will likely increase the market for OY15, as this species is the most widely cultured oyster worldwide. Prospective Research plans to make this probiotic strain commercially available. This transfer of natural and environmentally-friendly methods of controlling disease from the lab to commercial oyster aquaculture facilities will help increase sustainable aquaculture production.
Learn more about the NOAA Technology Transfer Program
For more information, contact Diane Kapareiko.
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.
Modeling to Predict the Spread of Oyster Disease
Oyster herpes virus OsHV-1 μvar has caused major die-offs of juvenile oysters in Europe, Australia, and New Zealand. The virus is a potential threat to U.S. oyster populations, as infected Pacific oysters have been detected in California. To evaluate the risk of spread and transmission of the virus in Pacific oyster populations along the West Coast, we are adapting a mathematical disease simulation model. The model incorporates oceanography, ecology, and epidemiology, and we are developing it in collaboration with our partners at the National Centers for Coastal Ocean Science, IFREMER, and Oregon State University.
Understanding and anticipating the risks this virus poses to U.S. oysters is important to protect both cultured and natural populations. The model will serve as a framework for disease management in aquaculture, informing practices and policies that promote aquatic animal health.
For more information, contact Meghana Parikh
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
Laboratory and Modeling Studies with Shellfish
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.
NOAA Fisheries Feature Stories:
- How Will Changing Ocean Chemistry Affect the Shellfish We Eat?
- Investigating the Effects of Ocean Acidification on Atlantic Sea Scallops
For more information, contact Shannon Meseck.
Field Studies with Atlantic Surfclams
Atlantic surfclams, one of the largest bivalves on the East Coast, support an economically important fishery in the Northeast U.S., with landings valued at just over $30 million in 2019. Both laboratory studies and modeling predictions from our Milford Laboratory indicate that this species is especially vulnerable to ocean acidification (OA). Previous research suggests that OA could cause surfclams to grow more slowly.
We are conducting field studies on Atlantic surfclams in coastal Massachusetts habitats to better understand how susceptible these shellfish are to the effects of OA. We will determine whether the results of lab experiments and model predictions match real-world results for this species. Each season, we will sample habitats and associated surfclams to find out whether their growth rate is correlated with the sediment chemistry where they live. We will use the results to refine our growth model for surfclams, so that we can better predict surfclam growth rates based on carbonate chemistry.
Because Atlantic surfclams burrow into the sediment, we are sampling seafloor habitats where surfclams live to better understand the carbonate chemistry of sediment and water in their habitat. While scientists monitor the chemistry of coastal and ocean waters, we currently know much less about changes to the chemistry of sediment and water in seafloor habitats. The effects of ocean acidification can also be amplified in coastal waters because this is where lower pH freshwater flows into the ocean. The Atlantic surfclam has two genetically-distinct subspecies, both of which live in Massachusetts waters. Spisula solidissima solidissima thrives in deeper water and off the northern coast of Cape Cod. This subspecies grows larger and has a longer lifespan than the southern subspecies, Spisula solidissima similis. The southern species is more tolerant of warm water and lower pH conditions, but is smaller and has a shorter lifespan.
By transplanting surfclams from northern sites to the southern sites, we can study environmental controls on subspecies growth, survival, and recruitment. During this experiment, we will measure the survival, size, and growth rate of transplanted and local clams, as well as study their genetics. We hope to find out which local conditions determine the subspecies present, as well as whether surfclams can adapt to OA conditions. In addition to the commercial fishery, this information will help recreational fishermen and the surfclam aquaculture industry.
For more information, please contact Matt Poach