Oyster Experiment Funded by US EPA – Much Needed Scientific Analysis of Oyster Nitrogen Removal Efficacy
In September, 2016 it was announced that UMass Dartmouth School for Marine Science and Technology (SMAST) researchers have been awarded $525,967 by the U.S. Environmental Protection Agency to determine whether the development of oyster colonies can help restore southeastern Massachusetts estuaries and salt ponds endangered by high nitrogen levels. The Westport River Watershed Alliance (WRWA) is thrilled to partner with the Coastal Systems Program (CSP) UMass Dartmouth (SMAST) on a new project funded by a grant from the US EPA Southeast New England Program for Coastal Watershed Restoration.
The grant is part of a $4.6 million program to develop innovative, cost-effective strategies to protect coastal waters in southeastern Massachusetts and Rhode Island. The projects are intended to identify, test, and promote effective new regional approaches in critical areas such as water monitoring, watershed planning, nutrient and/or septic management, and resilience to climate change.
The UMass Dartmouth initiative, led by Dr. Brian Howes and Dr. Roland Samimy at SMAST’s Coastal Systems Program, will use the Westport River and Cockeast Pond as a natural laboratory to measure how oysters can reduce nitrogen levels that destroy fish and other marine wildlife habitats. If proven successful, the strategy, which utilizes the natural power of the oyster to filter and clean water, could help reduce the need for high cost solutions such as expanded wastewater treatment systems. The first stage of the project is ongoing and involves a small scale viability test to determine if the oysters will survive in the Pond’s fluctuating temperature and salinity conditions. Assuming oysters are capable of surviving in Cockeast Pond, a larger scale experiment will be initiated in the summer 2017 using locally grown oyster seed from Riptide Oysters of Westport, MA. This full scale experiment will be geared towards measuring changes in nitrogen levels in the pond as a result of oyster filtration of the water column and the corresponding rebounding of native aquatic species. The experiment will be continued into 2018 and 2019 to quantify the effects on water quality in Cockeast Pond as the oysters grow to full size and to determine the most effective ways to deploy large numbers of oysters for maximum water quality improvement and minimum affect on the useability of the resource. So far just over 30,000 oysters have been placed in the pond in 15 cages, constructed of high quality, industrial grade vinyl coated wire. The full scale experiment will involve around 500,000 oysters over approximately 2/3 of an acre of the 90+ acre pond (less than 1% of the total pond area).
Deploying oysters in Cockeast Pond.
“Addressing the nitrogen problem along the SouthCoast, Cape Cod and the South Shore will cost billions of dollars if we only consider traditional strategies such as bigger wastewater treatment plants and more sewer lines,” Dr. Howes said. “We just don’t have the time or money for that course. It is, therefore, imperative that we find soft solutions that leverage nature, in this case the oyster, to make progress.”
These projects are funded through EPA’s Southeast New England Program (SNEP). Since its launch in 2014, SNEP’s mission has been to seek and adopt transformative environmental management. The program’s geographic area encompasses the coastal watersheds from Westerly, Rhode Island to Chatham, Massachusetts, and includes Narragansett Bay and all other Rhode Island coastal waters, Buzzards Bay, and southern Cape Cod as well as the islands of Block Island, Martha’s Vineyard, and Nantucket. While this research project is being undertaken in the Town of Westport, the results are meant to be transferrable to all the towns in the region that are seeking cost effective and innovative ways to push forward with estuarine restoration. Moreover, this investigation does not preclude the Town from looking into ways to reduce nutrient load from the Cockeast Pond watershed as a parallel effort.
Project Update November 2016
The Westport River Watershed Alliance (WRWA) is working with the Coastal Systems Program (CSP) UMass Dartmouth (SMAST) on a project funded by a grant from the US EPA Southeast New England Program for Coastal Watershed Restoration (see October’s River News for more info). The UMass Dartmouth initiative, led by Dr. Brian Howes and Dr. Roland Samimy at SMAST’s Coastal Systems Program, is utilizing the Westport River and Cockeast Pond as a natural laboratory to measure how oysters improve water clarity and potentially reduce elevated nitrogen levels which destroy fish and other marine wildlife habitats. Oysters get a lot of attention because they filter water. This can lead to the assumption that oysters are constantly removing nutrients from the water, but not all of the nutrients that oysters filter stay in their tissues. Many get deposited into the water or sediment as waste. While scientists have studied and quantified the removal of nutrients through harvested oysters, little is known about what happens to nutrients in waste and associated transformations that occur in the sediments exposed to oyster detritus.
Oysters’ ability to improve water quality by filtration has been well known, but many related questions remain. Such as, does oyster filtration always lead to nitrogen removal in nearby sediments? How much nitrogen is removed, and under what conditions? Do wild oysters have the same amount of nitrogen as those raised in aquaculture, and does this vary by location? And, can oysters’ work to remove nitrogen count toward nutrient reduction goals set forth in the TMDL (total maximum daily load)?
How do oysters remove nitrogen? Oysters are filter feeders; they remove particles from the water that contain nitrogen, primarily in algae (phytoplankton), and use it to build their tissues and shells or move it to bottom sediments in their biodeposits (pseudofeces). Benthic bivalves are important contributors of nitrogen (usually in the form of ammonium, NH4+) to both subtidal and intertidal systems. Once the nitrogen is in the sediments, microbes may break it down and release nitrogen gas into the atmosphere, a process called denitrification, removing nitrogen from the estuary. Also, all the nitrogen that is in any oysters that are harvested is removed from the system as well.
In September over 30,000 oysters were placed at four different locations in in Cockeast pond in 15 floating bags and 4 bottom cages, constructed of high quality, industrial grade vinyl coated wire. SMAST scientists have been checking on the oysters and after two months in the pond, they seem to be surviving well. Oysters in racks positioned in the lower west and east section of the pond, closest to the herring run were faring the best. The racks in the upper west and the mid-east sections of the pond showed some mortality. Survival/mortality was quantified at each location and a sub sample of oysters from each bottom cage was measured, weighed and brought back to SMAST to be analyzed for nitrogen content in the meat and shells. With the winter fast approaching, all the sets of racks and bags were sunk in 1.3 meters of water near the center of the pond. Next spring the full scale experiment will begin and involve around 500,000 oysters over approximately 2/3 of an acre of the 90+ acre pond (less than 1% of the total pond area).
WRWA is pleased to work with CSP scientists. Broadly, we are interested in the ecological services the oysters provide. Additionally, this research on oysters may help decision makers and citizens across the southeastern Massachusetts region understand the role of oyster reefs as natural capital, thus opening the door to greater investments in nature-based restoration techniques. This is more than just revitalizing an industry, it is the inherent ecological values of the oysters, including improving water quality and protecting shorelines we promote while also maintaining the unique cultural dimension of the region.
Also stay tuned for periodic updates and future presentations. This is truly a great opportunity for the Town of Westport to get cutting edge research that is directly applicable to its nutrient management effort but also broadly beneficial to the region.
UPDATE SPRING 2017
Last September over ~30,000 oysters were placed at four different locations in Cockeast pond in 15 floating bags and 4 bottom cages, constructed of high quality, industrial grade vinyl coated wire. After a few months, SMAST scientists sunk the oysters in deeper water to overwinter in the pond, they seem to be surviving well. Survival/mortality was quantified at each location and a sub sample of oysters from each bottom cage was measured, weighed and brought back to SMAST for analysis of nitrogen content in the meat and shells. This initial small scale deployment was a simple survivability test to determine if Cockeast Pond waters would be supportive of a large scale oyster deployment in the summer of 2017. By the end of June 2017, activities will gear up again as the full scale experiment will begin and involve adding around 500,000 oysters over approximately 60 m2 (less than 1% of the total pond area).
The project is using oysters grown by Westport’s own Riptide Oysters. The SMAST team is planning to deploy the oysters in one main location within Cockeast Pond; generally the southwest quadrant of the pond south of (INSERT NAME OF BIG ROCK in the middle of the pond). A secondary location was selected as necessary on the north-east side of pond. As a precursor to this work permits and permissions were secured from Army Corps of Engineers, the MA Division of Marine Fisheries, and the Town of Westport Marine Services Director.
WRWA’s role in this project is multi-faceted and will focus on both science and outreach. We will also be involved in the set-up of the various oyster gear as well helping with the deployment and maintenance of the oysters. Additionally, WRWA is helping with community outreach by distributing information to residents regarding the project and promoting its results on our website and social media, so stay tuned for updates.
Why Do the Study? We know oysters are filter feeders; they remove particles from the water that contain nitrogen, primarily in algae (phytoplankton), and use it to build their tissues and shells or move it to bottom sediments in their biodeposits. Once the nitrogen is in the sediments, microbes may break it down and release nitrogen gas into the atmosphere, a process called denitrification, removing nitrogen from the estuary. Also, all the nitrogen that is in any oysters that are harvested is removed from the system as well. The oysters in the experiment will not be harvested, but transferred to areas to depurate (clean-out) as they reach specific size limits with the hope that after the four year experiment is completed, an historic oyster bed in the East Branch of the Westport River will have been repopulated.
Not as well understood, however, is the amount of nitrogen that is either sequestered via deep burial in bottom sediments or returned to the atmosphere via denitrification. Determining rates of sequestration and denitrification is much more difficult than estimating nitrogen removal by harvest.
UPDATE SUMMER 2017
Much precursory work has been done to measure water quality in the Pond. WRWA invested nearly $60k to fund a multi-step, phased scientific study to determine the pond’s water chemistry, nutrient balance (nitrogen) and ecological health, all leading to recommended actions for remediating, restoring and maintaining the pond’s health. The USEPA funded oyster experimentation developed as one action to investigate as a soft solution for improving water quality in Cockeast Pond. Thus a project was designed; a grant was written, and fortunately selected for funding. Last year the experiment began with an initial small scale deployment of oysters to determine the spatial distribution of growth and survivability as well as sediment suitability. For more information of the project history and progression visit: https://westportwatershed.org/whats-being-done/oyster-experiment-in-cockeast-pond/
Full Experiment Begins
On July 11 and 12, 2017 the full scale experiment was launched and involved adding around 500,000 oysters to the Pond. WRWA worked with CSP scientists, students and interns to assemble the oyster gear; 250 cages were constructed. The project is using oysters grown by Westport’s own Riptide Oysters. WRWA helped to count, sort and distribute two-thousand oysters into each cage. Each oyster was approximately 8mm in size. The cages were stacked and placed over approximately 60 m2 in the Pond (less than 1% of the total area) surrounded by small orange buoys. And now we let the oyster sit and filter – throughout the summer and fall we will be checking and cleaning the gear.
Next Steps for project:
- CSP Scientists will evaluate the efficacy of deployment approach (surface bags, mid-water bags, or bottom racks)
- Ongoing water sampling for the Pond. The sampling and chemical analyses will include the full suite of nutrient related water quality parameters as in previous water quality monitoring done for the Pond and the Westport River to be directly cross comparable to long term records. Weather, tide-status, and results of water quality monitoring will be documented, with sampling performed so as to minimize both tide (ebb tide sampling) and weather-related effects on samples. Salinity measurements are also correlated to rainfall and other relevant parameters.
- Time-series dissolved oxygen (DO)/Chlorophyll-a Moorings = intensive sampling.
- Determining oyster bio-deposition rates and bio-deposit impact areas.
- Sediment core incubations and analysis of denitrification and oyster bio-deposits.
- Determine the net effect oysters have on nitrogen removal from Cockeast Pond.
- At the end of the experiment, as oysters in Cockeast Pond reach maturity, they will be transferred to an area of the East Branch that has previously supported oysters as a mechanism for re-establishing that natural population.
UPDATE FALL 2017
We reported in August that the full experiment, to quantify the amount of nitrogen pollution oysters can remove from Cockeast Pond, was in the water. This involved adding more than 500,000 oysters into floating gear placed in the Pond. The oysters have been in the water for over two months now, and we are seeing good survival and growth. Here are some of the tasks we’ve been working on with the team from the Coastal Systems Program (CSP) at UMASS Dartmouth.
Since July, WRWA has worked with the CSP team to provide field support in the determination of spatial distribution, survivability, viability and mortality of the oysters. Survival rates look very good with more than 90% surviving so far. Some of the oysters even quadrupled in size. The larger oysters were transferred into newly built cages with larger mesh to allow for better water flow.
We wanted to update you on the status of the project. Over the last year WRWA staff and volunteers have put in many hours to assist CSP scientists with multiple research related tasks. Half a million oysters have been in the water since August, and we are seeing good survival and growth.
To date, all the year 1 objectives for the project have been achieved as originally planned. In December we helped with the last oyster sorting for the year, where WRWA provided field support to help measure, sort, and determine survival rates. The oyster cages were lowered to a depth just off the sediment surface in the pond to prevent the oysters being frozen by icy pond waters and gear being damaged. Over the winter, the project team will be considering the merits of expanding the oyster experiment by including another 500,000 oysters to the previous deployment bring the entire experiment up to 1 million oysters. In the early spring, we’ll work with the CSP team to refloat the cages and begin the sorting, counting, measuring and water quality measurements again. The work will culminate after four years of monitoring, and as oysters in Cockeast Pond reach maturity, they will be transferred with the help of the Westport Marine Services Director to an area of the East Branch that has previously supported oysters as a mechanism for re-establishing that natural population.