Milford Lab: Environmental Research
Bivalve aquaculture can greatly increase food production, and enhance natural harvests, but methods must be compatible with the environment, habitat, and natural ecology. The goal of our research is to evaluate aquacultural practices by experimentally measuring the biological, chemical, and physical effects of existing aquaculture activities on habitat and ecology. Some activities, such as hydraulic dredging, cause initial disturbance to benthic organisms, but our data indicate that effects are generally short-lived with rapid ecological recovery. Other studies have shown that fixed shellfish aquaculture gear can provide habitat for many organisms and standing stocks of filter feeding bivalves can reduce nutrient loads. Our research goal is to evaluate specific aquacultural practices objectively to help assure that farming practices are sustainable. Marine spatial planning for development of aquaculture will allow for multiple uses of the coastal zone to co-exist and will identify optimal areas for production. Current research activities include conducting cooperative experiments with the shellfish industry to evaluate cultivation practices, and describing physical, chemical, and biological characteristics of shellfish habitat.
As the demand for aquacultured shellfish increases, so do concerns about possible environmental consequences of shellfish aquaculture expansion. Our group studies the complex interactions of shellfish aquaculture with the surrounding environment. We quantify environmental and shellfish variables, including inputs and outputs of nutrients, plankton and other chemical, physical parameters. Our research also incorporates various time scales from minutes to months. Our findings have highlighted the importance of local nutrient and plankton dynamics, as well as hydrodynamics. The scale of aquaculture setting in a particular site is also crucial in defining interactions. Our findings contribute to siting and scaling decisions made by farmers and by regulatory agencies, including the Northeast Regional Office of NMFS.
Milford Laboratory staff are using GoPro cameras to document habitat services provided to fish by aquaculture gear in Long Island Sound. Off-bottom oyster cages are an increasingly common method for culturing oysters. These cages create complex 3-dimensional structure that may provide habitat for fish and other animals. Shellfish growers routinely observe fish at a variety of life stages interacting with aquaculture gear on their farms. Oyster farms with large numbers of cages may act as artificial reefs attracting and aggregating a variety of fish species.
Researchers at Milford are conducting a series of field trials to 1. Determine how oyster cage density influences fish abundance and behavior 2. How fish interactions with oyster cages compares with fish activity on natural habitats such as boulders on a rock reef.
To record video of fish activity in and around oyster cages, these cages were equipped with two Go Pro Hero 3+ cameras. One camera was mounted like a periscope to view the upper cage surface, and a second camera mounted at one corner to capture activity along two sides and the cage bottom. To collect video on rock reef habitat, "T-platforms" were constructed to provide a mounting surface for two cameras. Divers then positioned each T-platform and cameras next to a boulder to provide a field of view similar to cage-mounted cameras. Preliminary analyses of fish behavior suggest that fish utilize oyster cages in a variety of ways such as foraging, station keeping, and during courtship. We are working with regulators and fishery managers who make decisions about siting shellfish farms and protecting habitat for recreationally and commercially important fish species. Our data will help inform their decision-making process.
A two-year, collaborative study evaluating the potential for aquacultured ribbed mussels to be used to extract nutrients from the Bronx River in New York City yielded important findings about the nutrient and plankton dynamics in that body of water. We discovered that the area studied at the confluence of the East River Tidal Strait and the Bronx River is a high-nutrient, low-chlorophyll (HNLC) system, which has important implications for nutrient management of western Long Island Sound, but also makes the site unsuitable for substantial mussel growth. Based upon these findings, we collected data at two locations in upper Narragansett Bay, RI, with more classic symptoms of eutrophication – high chlorophyll levels and seasonal hypoxia. Data from these sites are being analyzed.
We have also contributed to a modeling effort, led by Suzanne Bricker of NOAA NCCOS, to examine the potential for shellfish aquaculture to remove nitrogen at the scale of whole estuaries (Long Island Sound and Great Bay, NH). We provided local data on environmental conditions and oyster feeding physiology for use in the ecosystem and farm models. Results from this project are expected in early 2015.
In 2015, we will begin a study in collaboration with the town of Greenwich, CT, with a substantial coastline in western Long Island Sound and very active municipal shellfish management. Working with a resource economist at Stony Brook University, we will attempt to quantify local, economic benefits of the ecosystem services realized from existing and potential shellfish aquaculture, including improvements in water quality derived from filtration and assimilation of phytoplankton and associated nutrients in shellfish that then are harvested from the environment.
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.