Tag Archives: crown conch

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The Apalachicola Bay Situation Report: A Quick Take

Rob Diaz de Villegas WFSU-TV
The leaders of SMARRT look on as Dr. Karl Havens presents the Apalachicola Bay Oyster Task Force's report.

The leaders of SMARRT look on as Dr. Karl Havens presents the Oyster Task Force’s report.

This past Wednesday researchers from the University of Florida Oyster Recovery Team presented their report on the state of Apalachicola Bay to a public audience at the Apalachicola Community Center.  In the months since a Fishery Disaster was declared in the bay, this task force was formed by researchers from the University of Florida and our collaborator, Dr. David Kimbro (who was at Florida State University and is now at Northeastern).  They collected and analyzed historical sets of data and collected new data from the field to look at current conditions, their causes, and potential future actions aimed at restoration.  Here is a quick look at what was discussed:

  • In his introductory presentation, Dr. Karl Havens (Director of Florida Sea Grant) included an image in his PowerPoint depicting how the Apalachicola/ Chattahoochee/ Flint Basin was affected by recent drought conditions.  He called attention to an area of extreme red, approximately over the Flint and Chattahoochee rivers in Georgia, stating that “in 2011, and 2012, it was the driest place in the entire United States.”  Those rivers feed the Apalachicola.
  • Landings data (oyster harvest reported) show a sharp decline in oysters between August and September of 2012.  The suddenness of the decline, said Dr. Havens, is not consistent with overfishing, which results in a gradual drop. (Page 12 of the report)
  • Dr. Steve Otwell cautioned that the reputation of Apalachicola oysters is being tainted by undersized oysters making it to restaurants.  It was acknowledged by representatives of SMARRT that certain individuals do harvest sub-legal oysters, and that a goal of SMARRT is to educate seafood workers about the legal catch sizes and the reasons behind them. When it comes to sub-legal oysters reaching consumers, Franklin County Seafood Workers President Shannon Hartsfield said, “It takes two.”  Someone has to harvest and bring a sub-legal oyster to the dock, and someone has to buy and sell it to restaurants.  SMARRT is the Seafood Management Assistance Resource and Recovery Team, an organization made up of seafood workers and buyers.
  • The report finds that the three inch legal size is effective in preventing “size overfishing,” if it is properly enforced. (Pages 12-13)
  • Concern was raised over out-of-state oysters replacing Apalachicola oysters in restaurants, and whether Apalachicola could regain the market.  Dr. Otwell pointed to Chesapeake Bay, which had its fishery collapse only to rebound as a premium product.
  • Using their ECOSPACE modeling tool, they projected the recovery of the bay under several scenarios.  The worst case scenario has the bay recovering in 2020.  That’s with no shelling or reduction in harvesting.  Reducing effort in 2013 and 2014 would bring it back a couple of years faster, but the best scenario is a harvesting reduction and an increase in shelling (200 acres a year for 5 years).  That scenario predicts recovery by 2015. (Page 17)
  • Three years after the Deepwater Horizon explosion, people are still concerned about the possibility of oil contaminated seafood.  Tests of oysters, blue crabs, shrimp and fish species showed little or no trace of chemicals associated with crude oil or dispersants. (Page 19)
  • Hanna Garland installs a rebar cage on the floor of the Apalachicola Bay, in which her and David's experiments will be safe from oyster tongs and boat props.

    Hanna Garland installs a rebar cage on the floor of the bay, in which her and David’s experiments will be safe from oyster tongs and boat props.  We will have videos explaining the experiment in the coming weeks.

    One goal of the Task Force is to set up ongoing sampling of the bay.  The Florida Department of Agriculture and Consumer Services (FDACS) has surveyed oysters living on the most harvested reefs in the bay, and that data was used in the computer modeling.  But where that work looked at number of oysters (legal and sub-legal), a more thorough look at conditions on the reef was deemed necessary.  That’s what David Kimbro and Hanna Garland have been working on.  They have already completed their survey of the bay and presented a snapshot of predator distribution, reef structure, oyster size, and of oyster mortality (Many of the oysters on the floor of the bay are “gapers.”  When they die, their shells open permanently).  You can read a brief summary of his results here.  Hanna is currently deploying an experiment featuring live oysters and spat tiles (watch a video on the Kimbro/ Hughes lab’s use of spat tiles here).  Through this, they will learn how spat (the next generation of oysters) and adults are surviving conditions in the bay, how well spat are growing, and how many are being eaten by predators.

  • Dr. Otwell had an interesting solution to two problems: harvesting crown conchs.  Those who have followed this blog (or harvest oysters) know that crown conchs can become a real nuisance on oyster reefs (though a potential benefactor of the equally productive salt marsh system).  A crown conch fishery would provide some income for seafood workers while relaxing the effects of a predator that can get out of hand when the water gets saltier (like in recent drought conditions). (Page 28)
crown conch meat

The queen conch (Strombus gigas) is a popular delicacy, but it is under current consideration as an endangered species. Interest is growing in using the related crown conch (Melongena corona, shown above) as a substitute meat.

The hope is that some of the partnerships and research work can continue despite a lack of funding, and even after the fishery recovers.  ”I’ve said it over and over and over again, most of our information comes from the really extreme low events,” said Dr. Bill Pine.  ”And we don’t know how these systems look during normal flow or high events.”  As he pointed out, research doesn’t always get done when the system is healthy, and that leaves gaping holes in the data.  Likewise, this unprecedented collaboration between seafood workers, the state agencies that manage the fishery, and the research community was created in crisis.  Will it survive as the fishery recovers?

Download a PDF of the full report here.

Coming up

The meeting on Wednesday was part of one of our busiest months of production for In the Grass, On the Reef.  This week alone, we went from one end of our viewing area to another, starting with an EcoAdventure on Slave Canal (towards the eastern end of our range) to Choctowhatchee Bay for a look at a different kind of oyster restoration project (that’s as far west as we air).  We tagged along on an oystering trip and got footage for videos dealing with another coastal ecosystem susceptible to drought: the salt marsh.  We’ve logged a lot of miles, and I have a lot of footage to put together.  Here is a preview:

David’s Apalachicola Bay research is funded by Florida Sea Grant.

In the Grass, on the Reef is funded by a grant from the National Science Foundation.

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Crown Conchs- Friend or Foe?

For today’s post, we shift our look at the ecology of fear from oyster reefs to the (often) neighboring salt marsh.  We know crown conchs are villains on oyster reefs, but might they redeem themselves “in the grass?”  If they live on the Forgotten Coast, it depends on what side of Apalachicola they live.
Dr. Randall Hughes FSU Coastal & Marine Lab
The Crown Conch (Melongena corona).

The Crown Conch (Melongena corona).

IGOR chip_ predators_NCE 150If you’re a fan of oysters and you read David’s previous post, then you probably don’t like crown conchs very much. Why? Because David and Hanna’s work shows that crown conchs may be responsible for eating lots of oysters, turning previously healthy reefs into barren outcrops of dead shell.  And we generally prefer that those oysters be left alive to filter water and make more oysters.  And, let’s be honest, we would rather eat them ourselves!

But, in something of a Dr. Jekyll and Mr. Hyde act, crown conchs can take on a different persona in the salt marsh. Here, the exact same species acts as the good guy, increasing the abundance of marsh cordgrass.  And more abundant marsh plants generally means more benefits for we humans in the form of erosion control, water filtration, and habitat for the fishes and crabs we like to eat.  How exactly does that work?

Periwinkle in Spartina predator experiment

The Marsh Periwinkle (Littoraria irrotata).

If you look out in a salt marsh in much of the Gulf and Southeast Atlantic, I can nearly guarantee that you’ll see a marsh periwinkle snail. Usually, you’ll see lots and lots of them. These marine snails actually don’t like to get wet – they climb up the stems of the marsh grass as the tide comes in. While they are up there, they sometimes decide to nibble on a little live cordgrass, creating a razor blade-like scar on the plant that is then colonized by fungus. The periwinkles really prefer to eat this fungus instead of the cordgrass, but the damage is done – the fungus can kill the entire cordgrass plant! So these seemingly benign and harmless periwinkles can sometimes wreak havoc on a marsh.

But wait a minute – if periwinkles cause all the cordgrass to die, then why do you still see so much cordgrass (and so many snails) in the marsh? That’s where the crown conch comes in.

Crown conch pursuing periwinkle snail

At the edge of a marsh at high tide, a crown conch approaches a periwinkle snail. As shown in the video above, the conch was soon to make contact with the smaller snail and send it racing (relative term- the video is of course sped up) up a Spartina shoot.

In marshes along the Gulf coast, there are also lots of crown conchs cruising around in the marsh (albeit slowly), and they like to eat periwinkles. Unlike other periwinkle predators such as blue crabs, the crown conchs stick around even at low tide. So when the periwinkles come down for a snack of benthic algae or dead plant material at low tide, the crown conchs are able to nab a few, reducing snail numbers. And fewer snails generally means more cordgrass.

Of course, the periwinkles aren’t dumb, and they often try to “race” away (again, these are snails!) when they realize a crown conch is in the neighborhood. One escape route is back up the cordgrass stems, or even better, up the stems of the taller needlerush that is often nearby. By causing periwinkles to spend time on the needlerush instead of grazing on cordgrass, or by making the periwinkles too scared to eat regardless of where they are sitting, the crown conch offers a second “non-consumptive” benefit for cordgrass. One of our recent experiments found that cordgrass biomass is much higher when crown conchs and periwinkles are present compared to when just periwinkles are present, even though not many periwinkles were actually eaten.

Periwinkle in Spartina predator experimentOn the other hand, if the periwinkles decide to climb up on the cordgrass when they sense a crown conch, and if they aren’t too scared to eat, then crown conchs can actually have a negative effect on the plants. This is exactly what David found in one of his experiments.  In this case, the tides play an important role – west of Apalachicola, where there is 1 high and 1 low tide per day, each tide naturally lasts longer than east of Apalachicola, where there are 2 high tides and 2 low tides per day.  The longer tides west of Apalach appear to encourage the snails not only to stay on the cordgrass, but also to eat like crazy, and the plants bear the brunt of this particular case of the munchies.

So even in the marsh, it turns out that crown conchs can be both a friend and a foe to marsh cordgrass, depending on how the periwinkles respond to them. And figuring out what makes periwinkles respond differently in different situations just gives us more work to do!

Music in the piece by Revolution Void.

In the Grass, On the Reef is funded by a grant from the National Science Foundation.

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Notes From the Field: Hermit Crab/Crown Conch Cage Match

Last week David connected the regional dots, noticing similarities in oyster reefs overrun by oyster eating crown conchs across North Florida, from the Matanzas Reserve south of Saint Augustine to Apalachicola Bay. That included a breakdown of what they found during surveys of the Bay. Below, Hanna Garland details one of her experiments mentioned by David in the post.
Hanna Garland FSU Coastal & Marine Lab

Gaining a better understanding of the beautiful yet complex habitats that border our coastlines require a significant amount of time surveying and manipulating organisms (as you may know if you have been following our research for the past three years!), and even so, there can still be limitations in whether or not we truly know what is “naturally” occurring in the system.  Unfortunately, pristine salt marshes, seagrass beds and oyster reefs are in a general state of decline worldwide; however, this only heightens our incentive to investigate further into how species interact and how this influences the services and health of habitats that we depend on for food and recreation.

For the past two and a half years we have been studying the oyster populations along 15km of estuary in St. Augustine, but it did not require fancy field surveys or experiments to notice a key player in the system: the crown conch.  Present (and very abundant!) on oyster reefs in the southern region of the estuary, but absent in the northern region, it was obvious that there were interesting dynamics going on here…and we were anxious to figure that out!

In hopes of addressing the question: who is eating whom or more importantly, who is not eating whom, we played a game of tether ball (not really!) with nearly 200 conchs of various sizes by securing each one to a PVC pole (with a 1m radius of fishing line for mobility) onto oyster reefs.  After six months (and still ongoing), the only threat to the poor snails’ survival appeared to be the thinstripe hermit crab (Clibinarius vittatus)!

Hypothesized that hermit crabs invade and occupy the shell of a larger crown conch in order to have a better home, we decided to further investigate the interactions between crown conchs and hermit crabs by placing them in a cage together (almost like a wrestling match).

After only a few days, the mortality began, and results showed a weak relationship between species and size, and appeared to be more of a “battle of the fittest”.

The implications of how the interactions between crown conchs and hermit crabs influence the oyster populations are still largely unknown, but knowing that neither species have dominance over one another is important in understanding the food webs that oyster reefs support…and that organisms occupying ornate gastropod shells can be lethal as well!

In the Grass, On the Reef is funded by a grant from the National Science Foundation.

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Predatory Snails Overrunning Florida Oyster Reefs

A couple of years ago, David wrote about what seemed to be a very locally contained problem.  An out of control population of crown conchs was decimating oyster reefs south of Saint Augustine. Now, he’s seeing that problem in other Florida reefs, including those at the edges Apalachicola Bay. In reviewing his crew’s initial sampling of the bay, he sees that the more heavily harvested subtidal reefs are being assaulted by a different snail.

Dr. David Kimbro FSU Coastal & Marine Lab

Along the Matanzas River south of St. Augustine Florida, Phil Cubbedge followed in the footsteps of his father and grandfather by harvesting and selling oysters for a living. But this reliable income became unreliable and non-existent sometime around 2005. Then, Phil could find oysters but only oysters that were too small for harvest. Like many other folks in this area, Phil abandoned this honest and traditional line of work.

In 2010, Phil was fishing with his grandson along the Matanzas River and spotted several individuals who seemed severely out of place. Because Phil decided to see what they were up to, we are one step closer toward figuring out what happened to the oyster reefs of Matanzas and what may be happening to the oyster reefs of Apalachicola Bay.

Before I met Phil on this fateful morning, I was studying how the predators that visit oyster reefs may help maintain reefs and the services they provide (check out that post here). My ivory-tower mission was to see if the benefits of predators on oyster reefs change from North Carolina to Florida. To be honest, I’m not from Florida and I blindly chose the Matanzas reefs to be one of my many study sites. And in order to study lots of sites from NC to Florida, I couldn’t devote much time or concern to any one particular site. In short, I was a Lorax with a Grinch-sized heart that was two sizes too small; I just wanted some data from as many sites as possible.

Hanna Garland (r) discusses with Cristina Martinez (l) how they will set up gill nets as part of their initial oyster reef research in St. Augustine.

But then I met Phil, heard about his loss, and understood that no one was paying attention to it. After looking around this area, my Grinch-sized heart grew a little bigger. Everywhere I looked had a lot of reef structure yet no living oysters. Being a desk-jockey now, I immediately made my first graduate student (Hanna) survey every inch of oyster reef along 15 km of Matanzas shoreline. I think it was about a month’s worth of hard labor during a really hot summer, but she’s tough. Hey, I worked hard on my keyboard!

With these data and lots of experiments, we showed that a large loss of Matanzas oyster reef is due to a voracious predatory snail (crown conch, Melongena corona). This species has been around a long time and it is really important for the health of salt marshes and oyster reefs (in next week’s post, Randall shows the crown conch’s role in the salt marsh). But something is out of whack in Matanzas because its numbers seemed to look more like an outbreak. But, why? Well, thanks to many more Hanna surveys and experiments, we are closing in on that answer: a prolonged drought, decreasing inputs of fresh water, and increasing water salinity.

David took an exploratory trip to Apalachicola Bay with the Florida Department of Agriculture and Consumer Services in the fall of 2012, where they found these snails.

We need to figure this out soon, because we see the same pattern south of Matanzas at Cape Canaveral. In addition, I saw conchs overwhelming the intertidal reefs of Apalachicola last fall. While these reefs may not be good for harvesting, they are surely tied to the health of the subtidal reefs that have been the backbone of the Apalachicola fishery for a very long time. Even worse, the bay’s subtidal reefs seemed infested with another snail predator, the southern oyster drill (Stramonita haemastoma). Is this all related? After all, according to locals and a squinty-eyed look at Apalachicola oyster landings, it looks like Apalachicola reefs also started to head south in 2005.

To help answer my question, my team began phase 1 of a major monitoring program throughout Apalachicola Bay in January 2013.With funding from Florida SeaGrant, my lab targeted a few oyster reefs and did so in a way that would provide a decent snap shot of oysters throughout the whole bay. With the help of Shawn Hartsfield and his trusty boat, a visit to these sites over a time span of two weeks and hours upon hours of sample processing back at the lab revealed the following:

(1) There is a lot more oyster reef material in the eastern portion of the bay;

(2) There are also a lot more adult oysters toward the east;

(3) Regardless of huge differences in adult oyster density and reef structure, the ratio of dead oysters to live oysters is about the same throughout the whole bay;

(4) Although the abundance of snail predators is not equal throughout the whole bay, it looks like their abundance may track the abundance of adult oysters.

These data do not show a smoking gun, because many different things or a combination of things could explain these patterns. To figure out whether the outbreak of  multiple snail predators is the last straw on the camel’s back for Apalachicola and other north Florida estuaries, we are using the same experimental techniques that Hanna used in Matanazas River. Well, like any repeat of an experiment, we had to add a twist. Thank goodness Stephanie knows how to weld!

Luckily, I have a great crew that is daily working more hours than a day should contain. As I type, they are installing instrumentation and experiments that will address my question. If you see Hanna and Stephanie out on the bay, please give them a smile and a pat on the back.

More later,

David

Click here to see graphs illustrating the increase in salinity in the Matanzas National Estuarine Research Reserve (NERR). The NERR System allows you to review data from sensors at any of their reserves, including Matanzas and Apalachicola.

Music in the piece by Philippe Mangold.

In the Grass, On the Reef is funded by a grant from the National Science Foundation.

Switching gears: from kayak to office cubicle

Hanna Garland FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150As fast as summer approached, it is now over; and for myself, it marks the closing of an intense field season and the beginning of my first year as a graduate student. However, this does not mean that the experiments, laboratory work, and data collection is put on hold. There is still plenty of work to check off the “to do” list that seems to never get any shorter.

My last post introduced the scientific question I was hoping to answer and the reason for studying the relationship between crown conchs and oysters in the Matanzas River as opposed to a different location. While I did not answer the question entirely (that would be far too difficult to accomplish in one summer), I was able to establish a strong, preliminary data set that I can now analyze and re-configure in order to improve upon this research next season.

Similar to methods described in David and Tanya’s posts, the construction of my experiment consisted of (much smaller) trenches dug for cage installation, Z-spar for attaching oyster spat to tiles, bumblebee bee tagging kits for marking appropriately weighed and measured oyster clusters, and various amounts of PVC for expensive data logger equipment housing. The fun meter never stopped ticking this summer in St. Augustine!

As I sit in my cubicle in my new office on campus, my mind cannot help but wander back to my life this summer driven by the time of low tide and whether I would have enough sunlight or energy to kayak out to one more site. To my surprise, the running of my experiment was manageable and actually became a relaxing routine. Data collection was divided into three categories: conch surveys, oyster health, and data logger maintenance. The number of conchs found on the experimental reefs was recorded in order to quantify the varying densities of these predators at each site. The health of the small oysters attached to tiles as well as the tagged larger clusters were assessed based on the number of live and dead. The data logging instruments record the water temperature, salinity and amount of tidal inundation occurring at each of my six experimental oyster reefs every five minutes (so there are a lot of data points to be analyzed here!) and require periodic scrubbing to remove algal and barnacle growth.

While the daily workload may seem light as far as stress levels; the fine print of every step of an experiment can be a tremendous mix of emotions. The hope for not just data but “good” data is something that all scientists share; however, this does not mean that conducting research needs to be filled with anxiety. The outlook that I aimed to have this summer was more based on the feelings of excitement and opportunity rather than high expectations that may or may not be met. To be able to conduct this study in such an ecologically rich environment surrounded by intelligent, supportive, and proactive people and institutions is an accomplishment in itself.

While my data set still requires endless hours of manipulation and analysis, the general outcome of my experiment this summer revealed that there is in fact an oyster health gradient occurring along the Matanzas River, with a change in health occurring around the Matanzas Inlet. In tandem with this increasing oyster mortality moving from my sites north of the inlet to the sites south; are high densities of crown conch populations on the southern reefs, with a decrease in these populations moving towards reefs north of the inlet. Furthermore, environmental factors (water temperature, salinity and tidal inundation data collected by my instruments) will be considered when looking at these patterns.

As a way to better quantify the health and size of the oyster community as well as the density of the resident species (such as crabs, worms, and other amphipods) that inhabit oyster reefs; I surveyed and sampled background reefs at each of my six experimental sites. Long story short, this meant that I randomly selected four new oyster reefs at each site in which I collected environmental data and basic reef characteristics (type of reef, location, dimensions), conducted conch surveys, and collected every living oyster cluster, dead shell, crab, piece of biota, etc. inside of a 0.25 x 0.25 meter quadrat. After washing away the mud, extracting the living organisms and preserving them in ethanol, and weighing, measuring, and recording each live and dead oyster, I have developed a solid database of the oyster reef communities at each of my sites. This will help to better describe the type and abundance of species present at each site.

Oyster reef communities impact us in more ways than providing a tasty appetizer at a restaurant. Not only do they provide a habitat for commercially and ecologically important species, but they also serve to locally improve water quality and prevent erosion. Oyster reefs are complex communities that are in a state of decline along the Florida coast. Unfortunately, unhealthy oysters cause unhealthy or collapsed resident species communities because these organisms depend on oyster reef habitats for food, shelter, and other important aspects of their life cycle. This experiment and preliminary data set provides insight to changing food web dynamics occurring not only along the Matanzas River but in all oyster reef communities.

Apalachicola oysters

Tasty as they are, oysters have a far greater ecological- and economical- value when they're alive in their oyster reefs.

Whether you are enjoying seafood for dinner or driving on a bridge over estuarine environments, keep in mind the important role each individual species plays in a larger community structure. Our actions upstream of these fragile habitats impact everything from microscopic worms to the maturing oyster spat and larger fish populations. As my project evolves, I hope to not only strengthen the scientific community but also raise awareness among people who unknowingly influence an aspect of oyster reef habitats.