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checking out oysters and reef balls

If you build it, oysters will come

Oyster beds off of the coast of Cedar Key, Florida. Seafood, fishing, Gulf of Mexico. UF/IFAS Photo by Tyler Jones.Globally, oyster reefs are in free-fall. Disappearing faster than we can restore them, oyster reefs are one of the most threatened habitats on the planet. They are also one of the most valuable. Oysters create structure favored by many fish and invertebrates. They are also great at filtering water, capturing carbon, and breaking wave energy. For these reasons and more, oyster reefs are prominent features of several living shoreline projects we are building with the help of the community in Cedar Key.

Meet the materials

Oysters cannot move around once they settle in place. Young oysters, called spat, are fairly picky about where they land. They need to attach to a hard substrate, and their preference is to settle on adult oysters. But oysters can also settle and thrive on a range of other materials. In Cedar Key, we are using four types materials to form the base of new oyster reefs. These are reef balls, oyster castle blocks, shell bags, and reef prisms. Read on to learn more about each of these materials and the progress we are seeing on each.

Reef balls
a reef ball reef close to shore

One of 16 reefs deployed off Airport Rd. in Cedar Key that is accruing oysters at a rapid rate. Photo: UF/IFAS, Tyler Jones

In mid-June 2020, our team worked with Reef Innovations to place 384 reef balls along Airport Rd. in Cedar Key. These are arranged into sixteen reefs and each reef is composed of two rows of twelve reef balls. The reef balls are sitting along the -2 ft depth contour, specifically chosen to put the maximum amount of surface in the optimal zone for oysters. In just two short months, the oysters have definitely moved in! Our team is monitoring the progress of these young oysters using exciting 3D modelling technology. Using this, we can track the growth of oysters and increase in complexity over time.


a blue crab in the hole of a reef ball

A blue crab rests and feeds in the hole of a reef ball. Photo: UF/IFAS Tyler Jones

You may remember that back in 2018 we installed reef balls at the UF/IFAS Nature Coast Biological Station. We reported promising results in 2019, and the oysters are still going strong today! Overall, oyster domes made of concrete (like reef balls) are a great choice for oyster restoration in our region if you have the capacity and the means to install them.

Shell Bags
Volunteers and project team members pose with bagged oyster shell.

Volunteers and project team members show off oyster shell bags they helped make. Photo: Keith Kolasa

Shell bags can be made from a range of materials but most are made from plastic mesh or synthetic fabrics. At the Joe Rains Living Shoreline, the bags are made from a nylon fabric mesh and filled with clam shell. But many other projects, such as the Centipede Bay oyster reef in Hernando County, use hard plastic mesh bags with recycled or fossilized oyster shell as filler. Shell bags are one of the most commonly applied oyster restoration approaches. This is because they are easy and cheap to make, light enough for volunteers to carry, and generally have good success rates. Our team has even found that many types of shell are able to recruit oysters equally well. However, shell bags are increasingly problematic because they introduce harmful plastics into the marine environment.

Oyster Castle Blocks
oyster castle blocks in a stack

Oyster castle blocks interlock to form reef structures.

June was a busy month for oyster enhancements in Cedar Key! We also constructed two point bar reefs using oyster castle blocks. Castle blocks are basically cinder blocks that are molded into a shape that easily interlocks. While many shapes are possible with these blocks, we stacked them in a linear pyramid configuration. Oysters and barnacles are already settling on the surfaces of the blocks!

Reef Prisms
placing a reef prism along the shoreline

Dr. Mark Clark places a reef prism in place along G Street in Cedar Key. Oyster Castle Blocks are also visible, behind Dr. Clark. Photo: UF/IFAS, Tyler Jones

Reef prisms are a new material developed by Dr. Mark Clark in the UF/IFAS Soil and Water Sciences Dept. In this configuration, they function very much like shell bags with the added benefit of being plastic-free! The basic materials that make up reef prisms are jute fiber erosion control mat and Cement-All rapid setting concrete. The jute mat is soaked in the concrete mixture and draped around a form. Once dry, the forms are removed and the prism is filled with shell and capped off. While there are many shapes and configurations possible, we are using the prism shape in the current project due to the ability to stack them in multiple rows.

close up of oyster spat on reef prism

Oyster spat are clearly visible on the reef prisms after just two short months. Photo: UF/IFAS, Tyler Jones

As far as oyster growth, reef prisms and similar forms made of the same material perform quite well. A pilot test of the material at the Joe Rains Living Shoreline yielded impressive oyster growth. Last week, we deployed almost 90 reef prisms along G Street in Cedar Key. About a third of the prisms were moved to G Street from another location, where they were submerged in the water. These prisms were already coated with small oysters, showing a lot of promise for the future use of this material for oyster reefs elsewhere.

Have you used any of these materials on your local shorelines? Or have you used other materials? Tell us about it in the comments, and stay tuned for more shoreline updates.

7 Comments on “If you build it, oysters will come

  1. Excellent, informative story! I had only been familiar with shell bags, so thanks for the lesson in reef building! How long did each of these projects take? It looks to me like it’s labor intensive.

    • Hi Chris – It varies by project but if you don’t take into account the planning and permitting, these projects ranged from 1 day to a few weeks to deploy. Building the materials is also a key part, and that also varies from days to weeks. Honestly, the planning and the permitting is the slowest step but it’s very rewarding when you get to deployment day!

  2. This is great news! You all do so we’ll reaching out to the public for help. I don’t know if it’s allowed but for those who don’t follow your page it may be beneficial to post this info on Levy county Word of Mouth FB page. I think you you all you gain a lot of followers and hopefully volunteers!

  3. Savanna, the JR-CSA prisms look very promising. How do you monitor/measure the recruitment/settlement on the oyster prisms? Typically with bags, you remove a sample bag. Do you just observe the outside of the prism?

    • Hi Rhonda,

      We are experimenting with different monitoring methods. In the first pilot test, we just did mass change measurements and visual surveys of percent cover on the outside. But with these we are trying some 3D surface modelling as well as quadrat methods. The monitoring technique is definitely something we are still working on. But we do not plan to remove any of the units like you suggest is common for shell bags. Open to ideas if you have any!

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