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Apalachicola Bay System Initiative (ABSI) Q & A

Answers provided by ABSI, current as of  05/05/2023.  This is a working document, meaning that as more data and information become available, we will update the page accordingly. For questions or comments, please reach out to Thank you!

Q1:  I see oysters, why can’t I harvest them?

            A:  It is currently illegal to harvest any wild oysters from Apalachicola Bay, including recreational harvest (see FWC article). Outside of Apalachicola Bay, wild oysters can be taken but only in places that are open to harvest. While there are oysters growing in several areas of the Bay, they need to remain untouched and in place to help build back the reefs and provide spat to aid in oyster growth and recovery.

Q2:  What is the condition of the oyster beds (disease, shell loss, etc.)?

            A: The oyster beds in Apalachicola Bay are severely depleted, and much of the historical oyster reefs are shell hash. There is some disease, and in the saltier areas, oyster predator populations are high, but the biggest problem is lack of good habitat. We really need to restore the reefs then give the oysters time to grow. If not, it will collapse again.

Q3: What oyster diseases can be found in the Bay?

            A: An excellent question! First, let’s make a distinction between a parasite and a disease. A parasite is an organism that lives on or within another organism (its host). The parasite receives a benefit from the host (the host is often food for the parasite) and the parasite causes harm to the host. The amount of harm a parasite causes can vary a lot. Some parasites have negligible effects on their hosts (think headlice: pretty gross, but not too harmful), other parasites can make their hosts very sick and, in some cases, can kill their hosts. Disease is the term we use to describe harm (manifestation of symptoms) caused by a parasite. 

In Apalachicola Bay, there are two parasites that commonly infect oysters. Importantly, neither of these parasites infect people. The first parasite is Perkinsus marinus and it causes what is known as “Dermo disease” in oysters. Perkinsus marinus infects about 50% of oysters in the Bay and it is thought to be not particularly harmful to Apalachicola oysters. In the Northeastern United States, Perkinsus marinus can be problematic and has led to major oyster die-offs. Members of ABSI are therefore keeping a close eye on Perkinsus marinus in Apalachicola while carefully investigating its effects on individual oysters.  

The second parasite is a flatworm (or trematode) called Bucephalus. Bucephalus is a parasitic castrator, meaning that it lives in oyster gonads and sterilizes its oyster host. Parasitic castrators are extremely common in molluscs like snails, clams, mussels, and oysters—they occur in virtually all molluscs around the world. These flatworms are natural players in ecosystems and, in some cases, can even serve as indicators of ecosystem health. As with Perkinsus marinus, we are keeping a close eye on Bucephalus and working to learn more about its impacts on Apalachicola oysters. 

Q4:  What is the best material or substrate for restoring reefs in the Bay?

            A: Different materials have been used to restore the reefs in Apalachicola Bay. Natural shell is great for oyster recruitment but is hard to find in large quantities, is easily moved around by currents and it can become buried in sediment. Fossil shell can fall apart and degrade fairly quickly. The most successful material so far has been small limestone rocks (about 2”). These do not move as easily, but they are prone to being buried in areas where currents are strong. Some of these problems may be solved by putting more material out to make higher reefs. Of all the materials used so far, only the limerock has persisted, and oysters have settled and grown on it; however, the oyster populations have not recovered. In 2021, ABSI deployed our first restoration experiment using three materials: shell, small limerock and large limerock.(5-8 inches) and the reefs were 18 inches tall. So far, the larger limerock material seems to be doing the best – it is more stable and provides more hiding places from predators, and after 14 months, market sized oysters appeared on these reefs.

Limerock, also known as limestone, is a type of rock that is made of calcium carbonate, but can be comprised of different mineral forms such as calcite or aragonite. Shells of oysters, clams, and snails that you pick up on a beach or find in the Bay are made of calcium carbonate. Limerock was formed millions of years ago as the result of an accumulation of shells, corals, algae, and ocean debris. Limerock is not toxic.  

Lime is produced when limerock or limestone are subjected to extreme heat, altering the composition from calcium carbonate to calcium oxide. Lime is frequently utilized in some environmental remediation practices and is capable of decreasing turbidity in water, neutralizing acidity, and eliminating impurities. Additionally, when lime reacts to seawater, increased levels of CO2 can be absorbed and the boost in alkalinity simultaneously moderates ocean acidification caused by equilibration with increasing atmospheric CO2. Lime has never been used for oyster restoration in the Bay.

In contrast, lye is an alkali metal used mostly in producing soap and paper products. Lye is also used in tissue digestion and has a completely different chemical composition than lime and/or limerock. Lye is not used for any restoration purposes within the Bay.

Q5: Why don't you use shell for your restoration experiments?

            A: We know that oysters like to settle on shell; it is their natural habitat and has successfully been used in the past for restoration and re-shelling programs. However, there are a few important reasons as to why ABSI is not using just shell in our restoration experiments.

Since the Apalachicola Bay oyster fishery collapse, millions of dollars have been spent on oyster restoration. Some of these projects used shell, which has become difficult in recent years to obtain in large quantities. Fossil shell was used instead, but neither shell nor fossil shell lasted very long - it was buried, degraded, or dispersed by currents and waves. One of the Florida Department of Environmental Protection (FDEP) projects used small limerock and this material held better than the shell, but still, the oyster populations did not recover.

The reefs in Apalachicola Bay are so badly degraded that they need to be built up to give the oysters a stable habitat, like a natural reef. ABSI built a series of experimental mini-reefs (30 ft x 30ft x 18 inches tall) on Peanut Ridge and Dry Bar, using shell, small limerock (~2 inches), and larger limerock (5-7 inches). The shell reefs were quickly blown flat, dispersed, and partly buried by the currents and waves. The small limerock reefs did better but became very compact and difficult to tong.  The larger limerock performed best. It provided a stable, secure base and market-sized oysters grew in 14 months.

The next step for the ABSI restoration experiments is to try building a base of limerock or concrete (which is more readily available and cheaper than rock), with a layer of shell on top. We are placing 16 small reefs (50 ft x 26 ft x 15 inches tall) on Cat Point and half of these will have 3 inches of shell on top. Our hope is that the rock and concrete will make a stable base for the shell so oysters can settle and grow on their natural habitat.

Q6:  What caused the collapse of the oysters?

            A: The most likely cause of the collapse is a number of factors all working together. There were a few severe droughts between 2007 and 2012 when the fishery collapsed. Droughts reduced the fresh water coming from the river, so salinity increased, allowing marine predator populations to thrive in the Bay. Oyster drills are particularly damaging to the Bay oysters. Additionally, oysters need hard substrate to settle and grow. A traditional part of oyster management is reef ‘shelling’ or ‘cultching’ where material is placed on the reef to replace material lost to harvest or natural processes. There was a historical shelling program in the Bay, but it was significantly declined with changes in the industry,so there was no consistent replacement of reef materials to build back the reefs. Both of these problems contributed to the decline in oyster populations, and harvesting was allowed to continue while the fishery was collapsing until 2020 when FWC closed harvesting for five years.  All of these factors contributed to the decline, but there is now concern that the Bay is also ‘spat limited’ in addition to habitat limited, which means there are too few adults to produce the next generation of oysters.

Q7:  What types of studies are being done in the Bay to ensure oyster recovery?

            A:  Studies cover a range of topics, including developing models to help identify the best places to restore reefs, monitoring oyster populations to understand their recruitment, growth, and mortality, and conducting a number of studies on different aspects of Apalachicola Bay ecology. We have also deployed experiments to assess the effectiveness of different materials, and the benefits of creating higher reefs. Additionally, we are producing hatchery spat (juveniles) using Apalachicola adults to determine whether these will help supplement wild spat and ‘kick start’ the system. The ABSI website has more information on our research efforts, and the 2021-2022 Annual Report has more detail on the different studies. 

Q8: What is the plan to make sure a collapse does not happen again?

            A: For the past two years, ABSI has been working with a Community Advisory Board made up of oyster harvesters, seafood industry, scientists, county and city leaders, extension office, business owners and residents, and management agencies -FWC, DEP, DACs, to develop an oyster restoration and management plan (see draft here). When the oyster populations are strong enough to support a fishery, FWC will allow oysters to be harvested and they will monitor and manage the oyster reefs based on a plan developed by the  ocal CAB committee. The plan will be adaptable to changing situations to help prevent another collapse.

Q9: Haven’t we studied the Bay enough?

            A: The first comprehensive ecological studies of the  Bay date back to the 1970s when the system was in much better condition. Since then, there has been a lot of research, but we don’t understand completely:

      1. Why the oyster populations collapsed so quickly
      2. Why they haven’t recovered despite millions of dollars of investment
      3. Whether their decline is a symptom of a larger problem in the Bay or an isolated problem
      4. What extent the oyster population collapse is impacting the larger ecosystem

Restoration efforts so far have not resulted in population recovery, and we need to understand why. Were past restoration projects designed to optimize success or would something different work better? Are there so few oysters that there aren’t enough spat in the Bay? We do know a lot, but there are still plenty of unanswered questions. ABSI’s research is a large-scale, multi-disciplinary long-term study that is specifically focused on trying to address these knowledge gaps, with the help of stakeholders that understand the history of the Bay.

Q10: Is ABSI going into the aquaculture business with the new oyster hatchery?

            A:  No, the ABSI hatchery is intended for research and restoration only. The purpose of the hatchery is to generate spat on shell and individual juveniles for restoration and research.  The ABSI Shellfish Hatchery is not permitted to sell seed for aquaculture. We are hosting an experimental hatchery that is designed to produce commercial quantities of seed in a very small mobile space to kickstart restoration in the Bay, but this is not a commercial enterprise.

Q11: What can I do to help?

            A: To stay informed on the progress, please explore more of our website, sign-up for the ABSI bi-monthly Newsletter via email, attend outreach events where we ask for public input, and reach out to us at Harvesting wild oysters, even for personal use, will undermine restoration efforts. If you see anyone taking oysters, please report to FWC ( 850- 617-7600). We also welcome volunteers (see opportunities here!) at the Marine Lab and can find plenty for willing helpers to do.