Oysters and islands focus of effort to clean up South Bethany canals

Date Published: 
July 4, 2014

The Centre for the Inland Bays wants to improve the water quality in South Bethany’s canals, and they’re floating a couple new tools for their environmental toolbox there: islands and oysters.

CIB Restoration Coordinator E.J. Chalabala told those gathered at a special lecture organized by the Fenwick Island Environmental Committee on June 27 that, in the wake of indeterminate initial results for South Bethany’s canal diffuser test project in the first of its two years, efforts in using “bio-enhancement to improve estuarine habitat and water quality of poorly-flushed residential canals” (the new project’s official title) are the next thing they’ll try.

“Not much water flows through there in the first place, so how can we improve that?” he said of the question the project asks. “The bubbler systems didn’t work very well, so now we’re trying oysters and floating wetlands.”

The bio-enhancement, in this case, will mean establishing both oyster cages and floating wetland “islands” in an effort to increase habitat for micro-invertebrates and directly use the growing oysters to filter the water in the dead-end canals throughout the west side of the town. If the effort proves successful, it could be expanded to other locations in the Inland Bays watershed, including Fenwick.

According to a report this spring from the South Bethany Canal Water Quality Committee, in its first year, the diffuser project involving two of the town’s canals seems to have helped eliminate the stratification of the canal waters with layers having extremely low dissolved oxygen (DO), which has caused fish kills in the past. However, the diffusers installed in the Petherton canal not only haven’t increased overall dissolved oxygen levels but have caused DO levels to drop, the committee found.

“The apparent reduction in DO level where the diffusers are located does not make intuitive sense,” the report notes. “The diffusers are adding oxygen, but where is it going? One explanation is that the oxygen is being used to reduce ‘muck’ on the bottom.”

That could indicate that an improvement might be seen over the longer term, but additional muck measurements going into the second year of the pilot project are planned for comparison.

“Time will tell. That is why the project is scheduled for two years,” committee members noted.

In the meantime, the CIB is looking to proceed with the new proposal, involving the oysters and floating islands. Chalabala said high-density oyster cages would be installed in one canal, with the floating “wetlands” adjacent to them, in an effort to pull pollutants from the water.

One goal will be to prove that the oysters can be massed in higher densities (something already tested to some degree in Fenwick’s oyster gardening project) and that they can survive several growth seasons and spawn.

Chalabala said they will work to document that oyster communities can reduce total suspended solids and chlorophyll (associated with algae growth) and that the wetlands will help increase dissolved oxygen levels and the biological diversity of the waters in which they are used. The effort will focus on a natural and aesthetic approach to making water quality improvements in back-canal areas, such as those in South Bethany.

He said a major aim of the project is to prove to officials with the Delaware Department of Natural Resources and Environmental Control (DNREC) that such project can, indeed, improve water quality in the canals. Plus, he said, “Nobody has come up with any other solution, other than drilling out to the ocean for flushing” the canals with a new tidal source.

Swimmable and fishable are goals for now-stagnant canal waters

In all, South Bethany has 5 miles of poorly-flushed dead-end canals, Chalabala noted. Poorly flushed, in this case, means that the average “residence time” for the water in the canals is more than three months before it moves out to get freshened up again, leading to stagnation and anoxic conditions, which such projects are hoped to eliminate.

In South Bethany, the end goal has been fishable, swimmable waters, which Chalabala said will be two of the three objectives for the project. For fishable waters, they will be checking for levels of dissolved oxygen, water temperatures, salinity, nitrogen and phosphorous levels, and turbidity (cloudiness). Aiming for swimmable waters will involve measuring bacteria present in the water. In addition, he said, they’ll aim to collect accurate rain data to address related stormwater issues.

The plan for the new project will involve placing oyster cages in the York canal in South Bethany, each containing about two bushels of young oysters — about 15,000 to 20,000 oysters in all. Chalabala said that number of oysters can be expected to filter 22 percent to 30 percent of the canal’s water volume, which is 2.689 million gallons at high tide. A single oyster can filter between 20 and 40 gallons of water per day.

“If we’re correct on the amount that doesn’t flush, we know we can at least hit that 22 percent mark,” he added.

The floating wetlands are already being used in Baltimore’s Inner Harbor, he noted, and now they’ll become part of the York canal, with eight islands encompassing 600 square feet and 1,200 plants. Each island will include about 10 to 12 marsh hibiscus, 80 black needlethrush and 60 smooth cordgrass plants, which Chalabala said were selected not just for their ability to improve water conditions but for their aesthetic value along the residential canal area.

“When we grow these plants, a nice root mat comes down, putting in dissolved oxygen,” he explained. “We hope to document some kind of water quality improvements.”

While the York canal will be the study site for the project, the Carlisle canal will serve as a control, with three monitoring stations (two in York and one in Carlisle) to be installed to continuously measure DO, turbidity, salinity, temperature and depth.

The oysters themselves will be monitored for mass and content (including both tissue and shell growth.

“We’ll monitor how big they’re getting, what they’re eating,” over the course of 18 months to two years of growth, he explained.

Protection of project area, aquaculture program a focus

In addition, the project calls for continuous video monitoring, both underwater and above ground.

“We hope to see fish swimming around the root systems,” Chalabala said, adding that the scientists know the water is comparatively cloudy but that it does clear up a bit during the winter, and that the above-ground monitoring will aim to prevent vandalism.

That’s not just to protect the oysters and the project data, but from a public health standpoint as, he said, DNREC officials are extremely concerned that people might be tempted to steal the growing oysters and eat them.

That would be a very bad idea, he explained, as temperatures in the canals could kill some of the oysters or they could become diseased, which could make people sick were they to eat the oysters used in the water quality project.

“That would give the oyster aquaculture program a black eye,” he noted of the potential impacts of such a situation, extending beyond its impact on the water quality project and into the brand new commercial aquaculture program in Delaware, which hasn’t even seen its first oyster cages put in place.

To make sure that point gets across to even the casual observer, the project will include marking the locked oyster cages with a “skull and crossbones” sign, indicating that the oysters within are dangerous and potentially deadly to eat.

“You don’t want to eat some of these. This is probably the worst water quality that is in some of these canals. It’s full of [harmful] nutrients, especially in the summer,” he emphasized. “We’re going to do everything we can to not allow that.”

Chalabala pointed out that Delaware is one of the only U.S. states that hasn’t yet seen the presence of the oyster disease vibrio, which can cause potentially fatal sepsis and cellulitis in humans who ingest the safe-seeming oysters or even just handle them.

That means the state’s oyster harvesters have four or more hours before their catch is legally required to be chilled, as opposed to the hour limit seen elsewhere, which requires harvesters to have on-board refrigeration. It also speaks to the impact that human illness contracted from oysters illegally taken from the water quality program could have on the state’s fledgling commercial oyster industry.

Chalabala said another concern for the project is the cages’ and islands’ impacts on boating — something upon which he said the CIB was trying to work with boaters.

The project will use the York canal — the widest in South Bethany’s canal system — as its testing ground, with the Carlisle canal for a comparison. The monitors will be placed at both ends of the system, to see what the water is like coming in and going out.

The oyster cages and wetland islands would, ideally, be distributed in clusters along the entire York canal, he noted, but could also be positioned in a layout such as nine groups at the end of the canal and five more at its inlet. Each of the oyster cages would be positioned between some of the floating wetlands.

“We do need some more permissions from South Bethany,” he added of the immediate future of the project.

Timeline set for project

A monitoring permit for the project was obtained in June of 2014, and a permit for the oysters also submitted last month. Monitoring equipment could be deployed this month, with the wetland islands put in place later in July or in August. In September 2014, the oyster cages would go into place.

Come December, Chalabala said, they would move to harvest dead vegetation from the above-ground sections of the wetland islands, both to help it grow better and to make it look more attractive.

The islands and oyster cages would stay in place in the canal until December of 2015, with analysis of the project’s impact taking place from then until May of 2016, with the final report due in September of 2016.

With a positive report, Chalabala said, the CIB could go to other municipalities in the Inland Bays watershed and say, “This is something we might like to try.”

“This is something we could try on your canals,” he told the Fenwick Islanders. “It could show a substantial difference.”

One of the differences could be in the growth of algae in the canals, which has been particularly heavy this year and in past years has required harvesters to remove it from the waters in South Bethany.

“There is too much nutrients in our bay,” Chalabala explained of the rampant growth of the algae, noting that people over-fertilize their lawns and ornamental plants, and that many still have septic systems that lead to harmful nutrients moving into the groundwater. “The algae grows and grows so quick because it has so many nutrients to eat,” he said.

Chalabala said solving that problem is one of the goals of such projects. “We want to see if we can make the water quality impact enough to decrease the nutrients and minimize the algal growth you’re seeing,” he added, saying that the “overnight” growth of massive amounts of algae has not been unusual in the Inland Bays during the last 10 to 20 years.

Beyond the aesthetic impacts of the algae on humans, he noted, the eventual sinking of the algae turns it anoxic, which means clams and eel grass present in the water will die, further reducing the viability of the habitat for a variety of fish and invertebrates and negatively impact the entire ecosystem.

“They know there is a problem, but they can’t fix it,” he said of efforts to get rid of the algae in the canals. Moves to eliminate septic systems in favor of central sewer, to encourage people to use less fertilizer and to keep “gray water” (such as the wastewater from outside showers) out of the canals have been made in recent years as part of organized work to reduce the nutrient load in the watershed.

Chalabala said he expected the planned change in the outfall of the Rehoboth Beach water treatment plant from the Lewes-Rehoboth canal to the Atlantic Ocean would be a boon for the northern Inland Bays, since it will remove that point source of excess phosphorous and nitrogen from the bay waters.

In addition, water quality projects such as the South Bethany canal project are hoped to reduce pollutants in the Inland Bays, which haven’t had a substantial natural oyster population in more than 30 years, according to the CIB.

“Without more oysters and more filtration from these bivalves, we’re going to continue to have a nutrient and algae problem,” he said. “It takes all of us to do the work,” he added.