Our Restore Our Shores (ROS) team is constantly working to bring the Indian River Lagoon back to good health through a variety of projects, including re-establishing oyster reefs in this important body of water as a natural water filter and habitat. We are always looking for ways to make our programs more effective and sustainable, and the results of an oyster reef project built in 2022 will guide how we move forward with restoration work using fewer man-made materials! Read on to learn more.
Our oyster reef project places shells in the lagoon to attract oyster spat, or larvae, to attach to the shells and form reef structure. In the past, we used plastic mesh bags (as was industry standard) to hold the shells together and line the bottom of the lagoon. In 2020, we began using gabions, or galvanized metal cages, on select oyster reef builds to test their success.
We found that on average, gabions (when compared side-by-side with bags) naturally recruited almost three times as many live oysters! This is great news as gabions are a plastic-free material, which aligns with our goals of reducing plastic pollution. The only downside to gabions, however, is that they have a higher cost and take more time to build than bags.
Last year, we tried another innovative way to recruit oysters using even less foreign materials while also cutting cost: gabion corrals. A corral involves building a border of shell-filled gabions, then filling the middle area with loose, recycled oyster shell. In March 2022, we installed our first corrals at Ryckman Park in Melbourne Beach as a pilot project to test their success in recruiting live oysters. The corrals were built side-by-side with equal-sized gabion reefs so that we could monitor them together.
“It takes several weeks or even months for oysters to begin growing on the shells we deploy, especially since oysters only spawn a couple of times a year from late spring through the fall,” said Conservation Manager Olivia Escandell.
One Year Later
Although we monitored the reef at Ryckman Park at its six-month mark, we were able to get a better idea of its success one year out. Recently, we went back to the site to evaluate how the corrals and gabions performed.
Our team expected that corrals may have lower oyster densities because the gabion metal may protect the shells from certain predators, whereas the loose shells in the corral are more vulnerable. So, what did we find?
“Generally speaking, oyster recruitment at this site was very good! Over the entire project, we had an average of 760 oysters per square meter after one year. In total, around 40,000 oysters have recruited to the 900 square foot project,” said Olivia. She noted that her team observed over 20 different species growing on the reef! This included oyster toadfish, porcelain crabs and barnacles. “We found that both designs were maintaining their structure very well after one year, despite going through hurricane season.” The largest live oyster our team found had grown to almost four inches in just one year!
How We Monitor
How does one evaluate this type of project? According to Olivia, the ROS team uses standard methods that are implemented by many other oyster restoration groups. “We remove predetermined, random samples of shell from both gabions and corral reefs. On shore, we sort through the shells looking for live oysters and any other organisms growing on the shells. We then measure the live oysters and record the total number in each sample,” she said.
Other conditions, such as salinity, water temperature, water depth and height of the oyster reefs are also recorded.
Corrals Vs. Gabions
When we monitored the site at six months, the oyster density was about the same on oyster gabions and corral modules. After one year, however, oyster density was slightly higher in oyster gabions than in corrals – which is what we predicted might happen due to vulnerability to predators.
Although oyster density was slightly lower on those pulled from corrals, we have decided to keep moving forward with this design on more oyster restoration projects for several reasons, First, corrals are doing well! Although their numbers were slightly lower, they are providing great habitat for live oyster larvae to grow on. Second, they use less man-made materials. Last, they will reduce our project cost and labor needed to assemble gabions. Gabion metal can be very expensive and time-consuming to put together, so using less of this material will reduce our expenses and labor. This may give our team an opportunity to complete more restoration projects!
The majority of our 20+ oyster projects this year will use oyster corral designs. We will even begin piloting oyster corrals with locally-sourced limestone walls instead of gabions to eliminate man-made materials entirely! Later this spring, ROS will be building oyster reefs with gabions and corrals along south Merritt Island. Over the summer, we will be establishing more oyster reefs in Melbourne, Indialantic and Palm Bay.
“We will continue to monitor the way corrals are performing and test designs that reduce man-made materials on projects while maximizing restoration potential and success,” said Olivia.
The Indian River Lagoon is central to our community’s well-being by providing food and recreation, while also supporting our region’s economy. We’re thankful to our Space Coast community for understanding this and helping us and other lagoon restorationists.
Our ROS team couldn’t do all of this amazing lagoon work without the help of partners! This oyster reef project was funded by the Brevard County Save Our Indian River Lagoon Project Plan and given the project site and support by the Town of Melbourne Beach. This project was inspired by the work of other restoration groups, including GTMNEER, FWC, Sarasota Bay Watch and Sea & Shoreline.
Our incredible volunteers help us with many ROS projects and provide the hands that we need to continue this critical restoration work. If you’re interested in being part of this good work, you can check out our current volunteer opportunities here! We hope to see you volunteering in the lagoon soon!
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