By Silas Tanner, Nikki Dix, Pam Marcum, & Shannon Dunnigan

Long-term monitoring of oyster populations is a big project at the GTM.

If you have driven over any of the bridges in northeast Florida at low tide, you know how expansive our oyster reefs are. Here locally we have intertidal oyster reefs, which means that they are situated at just the right elevation so that they are covered up at high tide, and have access to all the delicious plankton in the water, but exposed at low tide, to escape predators and disease.

So, why study and monitor oysters?

Because they’re cute?? No. Because they’re tasty? Well, sort of… Oysters are extremely valuable to coastal economies because people love to eat them. Packed full of essential amino acids and other nutritious vitamins and minerals, these bivalves have been a cultural favorite for a long, long time.

Spat, settled oysters, on an adult oyster shell

In addition to the numerous socioeconomic benefits of oysters, many ecological benefits are derived from a thriving oyster population. These include improved water quality, shoreline stability to combat erosion, provision of habitat for many species of fish and crabs, as well as oysters to eat!

Oysters have historically been an abundant food source in many estuarine regions. Within the GTM NERR alone, there are 20 documented oyster middens that date back to 1000 AD! A midden is an archeological feature that contains the debris of human activity. These shell middens were created by the Eastern Timucua tribe of Native Americans located here in northeast Florida. They contain a detailed record of what food was eaten or processed and even may contain fragments of stone tools and household goods.

The rich history of oysters extends locally, too. In the early 1900’s, the Usina family of St. Augustine used to have oyster roasts at shacks near the beach for tourists who came to visit via Henry Flagler’s railroad.

Enough local oysters were served during this time that the piles of shells were used for building roads, filling in holes, making septic tank drainfields, and even constructing homes. As with many things, as time moved on, things began to change. Increased development of the area – like the construction of the Guana Dam and dredging of the ICW waterway, among others- altered the condition of the water and flow patterns. Many local harvesters, including the Usinas, noticed declines in the local oyster populations.

“As with many things, as time moved on, things began to change.”

By 1995, water conditions had changed so drastically that many local harvest areas had to be closed.  Concern over the future of oysters in the area grew and that same year local harvesters, management agencies, and many others came together to form the GTM Shellfish and Water Quality Task Force. The goal of the task force was to identify research needs, determine potential sources of pollution, and make recommendations for improving management practices; all of which can be found in a Progress Report produced in 1997.

Despite best efforts, twenty years later most of the estuarine waters within the GTM boundaries are considered impaired for fecal coliforms by the state of Florida. In 2015, the task force was re-assembled into the Oyster and Water Quality Task Force of the GTM. The current task force includes several of the original members and even more agencies, researchers, and citizens that are concerned with the sustainability of local oysters and water quality. This task force is focused on promoting inter-agency collaborations to identify information gaps and prioritize research needs.

Here at the GTM, we have combined the needs of the task force as well as our own research questions to develop a long-term oyster monitoring plan. We monitor the condition of our oyster populations for a few reasons:

• How do we know if they’re changing if we don’t know where they started? By collecting long-term data, we can establish a baseline condition of the population so we can detect changes in the future.
• Oysters sit in the same place their whole life, filtering water with each tidal cycle, so they are great indicators of water quality. By monitoring where oysters are living, (and where they are not!) we can identify potential water quality issues and patterns.
• Oysters are tasty. But…we also need to understand how harvesting effects the population.
• There is a time and place for everything…including oysters! We evaluate seasonal and regional/water body differences in oyster populations to help us determine the best management practices to maintain healthy reefs.

Conducting oyster monitoring at the GTM Research Reserve

Conducting oyster monitoring at the GTM Research Reserve

So, why study oysters?  

Because…why not!?

The next time you’re slurping an oyster down, or just looking at an oyster reef as the sun sets over the Intracoastal Waterway, think about all the hard work these shellfish do for our estuary!