Category Archives: On the Reef

Dr. David Kimbro studies predator-prey relationships in the oyster reefs and salt marshes of Florida’s Gulf coast.

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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.

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Tile 2.0- Perfecting the Oyster Spat Tile Experiment

As we’ve been getting this post ready, David’s Apalach crew (Hanna, Stephanie, and Shawn) has begun deploying the experiment featured in the video above in Apalachicola Bay.  After years of perfecting it, the tile experiment has become a key tool in Randall and David’s oyster research.  As you can see, there were some headaches along the way.
If you’d like to know more about spat (young oysters), we covered that a few weeks ago in this video.
Dr. Randall Hughes FSU Coastal & Marine Lab

An “open” cage, with full predator access.

One of the primary goals of several projects in our labs involves figuring out where oysters grow and survive the best, and if they don’t survive, why not? Sounds pretty basic, and it is, but by doing this across lots of sites/environments, we can start to detect general patterns and identify important factors for oyster growth and survival that maybe we didn’t appreciate before. Our method of choice for this task is to glue the oysters to standardized tiles, place some in cages to protect them from predators, leave the rest to fend for themselves, and then put them in the field and see what happens over time.

In doing this lots and lots of times, we’ve learned who in the lab has a special knack for placing small drops of marine glue – Zspar (which you can see in the video) – on tiles, and who is better at adding the oysters so that the 2 valves of their shells don’t get glued shut. These are the sorts of crazy job skills that don’t go on a standard resume!

Any of you who have been following the blog for a while may remember the craziness of the our first NSF tile experiment (Tile 1.0) in the fall of 2010, which involved collecting lots of juvenile oysters (“spat”) that had recently settled in the field, bringing them back to the lab, and using a dremel to carefully separate that from the shell they settled on. (If you don’t remember and want to check it out, go here.)

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Two of our oyster “families” in the water tables at Whitney Marine Lab

Since the Tile 1.0 experience, we’ve developed more elegant (and much simpler!) methods: we contract with an amazing aquaculturist at a FL hatchery to collect adult oysters from the field, provide just the right ambiance to make them spawn (release eggs and sperm), and then raise the oyster larvae to a perfect size for attaching to our tiles. This year, we added another twist on this theme (Tile 2.0) by collecting adult oysters from different areas in FL, GA, SC, and NC, and then spawning and raising them separately in the same hatchery under identical conditions. We refer to these different groups of oysters as “families”, because all of the spat from a given location are related to one another, but not very closely related to the oysters from a different location (who had different parents).

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Evan and Tanya admiring our work after we deployed the first reef in St. Augustine.

By putting out tiles from each family at sites across this same geographic range (FL to NC), we can tell if some sites or regions are inherently better than others for oysters (for instance, as I’m currently learning first-hand, there’s a reason that everyone wants to spend the winter in FL!), or if some families are naturally better than others (think Family Feud with oysters), or if the oysters that came from a particular site do best at that site, but not in other places (like the ‘home field advantage’ that recently helped Maryland beat Duke in basketball). Whew – that was pretty mixed bag of metaphors! But you get the idea.

We’re still processing and analyzing the data from Tile 2.0, but it looks like which site is the best depends on what you’re measuring – the best place for survival is not always the best place for growth. And the different oyster families do look and “behave” differently – some grow quickly and some grow slowly, and some survive predators better than others.

Spat bred from adult oysters from Sapelo Island in Georgia (left) and ACE Basin in South Carolina (right).

Surprisingly, there doesn’t appear to be much of a home field advantage, at least from our initial analyses. And as Meagan pointed out, we’ve learned from other similar experiments for the National Park Service that it’s not just other oysters or predators that these guys have to worry about – it’s barnacles too! But there are still some ‘sweet spots’ out there for oysters, and once we’ve analyzed all of our data, we’ll have a much better sense for where those are.

We want to hear from you! Add your question or comment.
Music by Barnacled and Pitx.

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

 

Mud crabs (like the one pictured here), oyster drills, and crown conchs are the primary consumers of oysters on the reef.

How Do Predators Use Fear to Benefit Oysters?

Over the last few weeks, we’ve explored the concept of the ecology of fear on oyster reefs. But, as David asks in the video, “does it matter?” Exactly how much does fear affect oyster filtration, or their ability to support commercially and ecologically important species? And how does fear affect the benefits we receive from ecosystems such as salt marshes and seagrass beds? Coming up, we see how David and Randall took these big questions and broke them down into a series of experiments and investigations geared at creating a clearer picture of fear in the intertidal zone.
Dr. David Kimbro FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150A few weeks ago, we had a bayside conversation about the important link between nutrients and oysters. But there is something else that may dictate whether a reef thrives: predators.

Academically, the importance of predators dates back to the 1960s. Some smart people proposed that the world is green because we have lots of big animals, which eat all of the smaller animals that would otherwise consume all the plants…hence the green world.

busycon eating moon snail

Busycon spiratum eating an Atlantic Moon snail on Bay Mouth Bar. These seagrass beds off of Alligator Point are home to the greatest diversity of predatory snails in the world. In the late 1950s and early 1960s, Dr. Robert Paine investigated the effect of the horse conch, the most dominant predator among the snails, on the habitat. David and his crew have similarly used the dynamic invertebrate population to test their theories on the ecology of fear. (click the photo for more on Bay Mouth Bar).

Now, that’s a pretty simple yet powerful concept.  Since then, lots of studies have tested the importance of predators and how they keep our world spinning. For example, Bob Paine relentlessly braved the icy waters of the NW Pacific for a decade in order to chunk ravenous sea stars from one rocky cliff, but not the other. After several years, the cliff with sea stars still had a tremendous diversity of sea creatures (algae, anemones etc.) and the cliff without predatory sea stars did not. The absence of sea stars allowed pushy, bullying mussels to outcompete all other animals for space and this gave the rocky cliff a uniform and boring mussel complexion.

The same concept has been tested on land. Ripple and Beschetta showed us why the national parks out west no longer have the really important and woody trees (aspen, willow, and cottonwood) that they historically had. By suppressing wolves for the last 50 years, we allowed elk numbers to explode and the elk have overrun the really important woody species.

But predators don’t just eat.  Enter my vivid memory of trying out for the Nash Central 8th grade football team in rural North Carolina. Contrary to my father in-law’s belief (who is a hall of fame football coach in Georgia), I wanted to play football instead of soccer.  But when it came time for try-outs, fear prevented me from pursuing this line of work.  To practice breaking tackles, each player had to lie on the ground and the rest of the team formed a circle around this player.  Unbeknownst to the guy on the ground, the coach secretly selected three players to tackle the football player at the sound of the whistle.  For twenty minutes, I watched physically un-developed friend after late-blooming friend get crushed by other guys who were definitely not late bloomers. The sights and sounds of this drill kept me nauseous until it was my turn. When my turn came, I couldn’t deal with the fear, didn’t perform well, and consequently became a soccer player.

My point is that fear is very powerful. Of course, I knew the charging football players were not going to eat me. But if I was paralyzed with fear from football, then imagine what it’s like for something that has to worry about being eaten. Going to back “the world is green” story: what if we overlay the concept of fear on that? How does the story change?

Well, the next generation of predator studies has examined how the fear of predators can be just as important as the appetite of predators. In addition, because predators can only eat only one animal at a time but can simultaneously frighten many more, fear can create powerful “remote-control effects”. In Australia, the fear of tiger sharks causes dugongs to avoid certain depths in a bay. As a result, only a small portion of the seagrass beds get grazed down by dugongs, possibly being one of the main reasons why areas like Shark Bay still have huge and lush seagrass meadows.

Mud crabs (like the one pictured here), oyster drills, and crown conchs are the primary consumers of oysters on the reef.

For the next few weeks, we will look at some work that my friends and I have conducted for the past three years on how predators and the fear of predators influence oyster reefs and the services that they provide us throughtout the southeast. Although we have the same predators and things that like to eat oysters from North Carolina to Florida, we suspect that differences in the environment will cause the effect of predators to play out differently.

In parting, I just want to say that this predator stuff is really interesting and I think it’s very important for oyster reefs. But of course, when you are dealing with an ecosystem that may be on the verge of collapse like Apalachicola Bay, the distinction between the appetite and fear of predators may not matter that much. But, we will soon see because we are now investigating this important system too.

We'll be following the Apalach study as well. Here, Stephanie Buhler, who we had previously seen diving in Apalachicola Bay, welds a cage to house an upcoming experiment in that research. It's a variation of the tile experiments that became such a staple of the NSF oyster study. In a few days, we break down the tile experiment, and David's collaborator, Dr. Randall Hughes, talks about what the results are telling them so far.

Music in the video by Revolution Void.

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

Barnacles overtaking the experimental oysters.

Notes from the Field: Overwhelmed Oysters

Meagan Murdock is a lab technician in the Hughes and Kimbro Labs, operating out of the FSU Coastal and Marine Laboratory. The experiment she describes in the following post is a central staple in the research conducted by Dr. Randall Hughes and Dr. David Kimbro into oyster reef ecology. They seek to measure factors affecting the health of an oyster at a given location by monitoring the growth of young oysters (spat) in a controlled unit- the spat tile. We’ll be further exploring the use of spat tiles in their NSF funded oystern study in the next couple of weeks. David Kimbro is also gearing up to deploy a tile experiment in Apalachicola Bay, with the goal of measuring conditions there (see photo below).
Meagan Murdock FSU Coastal & Marine Lab

Beautiful reef backing up to red mangroves (Rhizophora mangle) in Mosquito Lagoon, FL. Notice our experiment on the reef!

Mosquito Lagoon of Canaveral National Seashore is in the northern section of possibly the most diverse estuary in North America, the Indian River Lagoon. But don’t let the name “Mosquito” Lagoon scare you off! This lagoon is an expanse of mangrove islands, oyster beds, and home to charismatic animals like manatees and dolphins (maybe a few mosquitoes, but where in Florida can you not find mosquitoes??).  Eight months ago, we set up a rendition of the “Tile Experiment” at three National Park Service units in hopes of elucidating factors contributing to oyster spat (spat=newly settled oyster) survival and growth. Last week we ventured out to Mosquito Lagoon to check on our baby oysters and this is what I found. The tiles were covered in BARNACLES!

Tile 75 pictured after being deployed for 2 months and 8 months.

I felt bad for the little oysters. Not only are these spat expected to survive through adverse environmental conditions and hope they do not become some crab or fish’s dinner, but they also are competing for space and resources with other filter feeders. Geez it must be tough being an oyster! But-yeehaw!-the oysters are persevering and I got to enjoy the nice weather of Central Florida.

Barnacles overtaking the experimental oysters.

As Meagan continues to monitor the growth of her Canaveral oysters, David is having Stephanie Buhler and Hanna Garland deploy some test tiles in the subtidal (always submerged) oyster reefs of Apalachicola Bay.  The tiles will be protected by a steel cage which will allow access to researchers while protecting the experiment from an oysterman’s tongs.  Different prototypes of tiles and cages were deployed last week with the full experiment to begin in the coming weeks:

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

Experimental spat tiles, open, closed, and partially open.

Fear and the Choices Oysters Make

Last week, Dr. David Kimbro broke nutrients and oysters down for us.  But what if oysters are too scared to eat the nutrient fed plankton they need to survive?  David and Randall take us another step closer to understanding the Ecology of Fear, examining oysters’ choices and how their behavior affects the important habitat they create.  Stay tuned over the following weeks as they unravel the relationships between predators and prey on oyster reefs and their neighboring coastal ecosystems.  We’ll also continue to follow David’s crew in Apalachicola, Hanna and Stephanie, as they research the oyster fishery crisis.

Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150I recently moved and was faced with the dilemma of finding a place to live. This can be a touch decision, especially when you’re in a new city or town. Which neighborhood has the best schools? The best coffee shop? Friendly neighbors? Low crime? My solution was to find something short-term while I scope the place out some more, and then I can decide on something more permanent. (As anyone who has me in their address book knows, “permanent” is a very relative term – I have changed residences a lot over the last 15-20 years!) But imagine you had just one shot – one, for your whole life – to decide where to settle down. Talk about a tough decision! That’s what oysters have to do, because once they settle down and glue themselves to their location of choice, they don’t have the opportunity to move around any more. So how do they decide?

This oyster shell, harvested from an intertidal St. George Island reef, had been settled by multiple young oysters called spat. Spat grow into mature oysters with a hard shell, fused with the oyster on which they originally landed. Clumps of attached oysters form a crucial coastal habitat.

It turns out that oyster larvae (baby oysters swimming in the water) can use a number of “cues” to help them in the house-hunting process. First of all, they can detect calcium carbonate, the material that makes up oyster shells (and other things) – if there’s lots of calcium carbonate in an area, that could be a good sign that it’s an oyster reef. (Or it could be a sign that people have put a lot of cement blocks in the water in the hopes that oysters will settle and create a reef – that’s how a lot of oyster restoration projects are started.) Some recent research even shows that oysters can detect the sounds of an oyster reef, and then swim in that direction! Maybe these guys are smarter than we think…

Regardless of how oysters decide, there are times when we are also faced with the question of what makes good oyster habitat, or deciding which area is better than another. As scientists, we turn to experiments. One type of experiment that we have perfected over the years involves getting juvenile oysters- (either from the field, which can be pretty difficult -as you can see from the first round of our tile experiment, or from a hatchery), and gluing them to portable sections of “reef” (ceramic tiles weighed down by bricks). LOTS of ceramic tiles and bricks. We’re talking 800+ ceramic tiles and 700+ bricks last summer alone! That’s enough to make a path that is ~2 football fields long. All moved by truck, hand, boat, hand, kayak, and hand to their temporary location on a reef (and then moved back again when the experiment is done). But I digress.

In the second incarnation of the tile experiment, oyster spat were attached to tiles with an epoxy used in the repair of boat hulls. The tiles in the first version- the ones in the video above- were assembled differently. In a video we'll premiere later this month, we'll look at the twists and turns the experiment took.

After attaching the juvenile oysters to the tiles with a lovely substance known as z-spar, we enclose some tiles in cages to protect them from oyster predators, and we leave others with no cage so they are “open” to predators. (There’s also a 3rd group – the “cage control” – that get 1/2 a cage so we can test whether the cage has effects on the oysters other than keeping out the predators.) Then we take our oyster tiles and put them out in the field at different sites that we want to test. By observing the survival and growth of the ones in the cage (where no predators have access), we can get a general sense for whether it’s a good environment or not. Lots of large, live oysters are a sign of a good environment – plenty of food, good salinity (not too salty or too fresh), good temperature, etc. Also, by comparing the survival of the ones in a cage vs. not in a cage, we can get an idea of how many predators are around – lots of live oysters in the cage and none out of the cage is a pretty good sign that oysters are getting eaten. (If oysters in the cage are dead and oysters outside of the cage are missing, it’s a little tougher to figure out exactly what’s causing it, but it’s clearly not a good place for oysters to live!)

Experimental spat tiles at the Guana Tolomato Matanzas National Estuarine Research Reserve- open, closed, and partially open.

Of course, the oysters themselves don’t know whether they are nice and safe inside our cages, or easy pickings for a predator. So if there are lots of predators lurking around the reef, the oysters may try to “hide”. Obviously, hiding for an oyster does not mean packing up and moving elsewhere, but they do have a few tools at their disposal. In the short term, the oysters can choose not to open up their shells and feed (filter water) as often. This strategy has 2 benefits – 1, they are less vulnerable to predators when their shells are closed and 2, they aren’t releasing lots of invisible chemical cues in the water when they’re closed, so it’s harder for the predators to tell they are there. But as any of you who have been sticking to your New Year’s resolution to lose weight will know, there’s only so long that you can go without eating before that strategy loses its appeal! Over the longer term, the oysters can decide to devote more of the energy that they get from eating to create a thicker, stronger, rougher shell, rather than plumping up their tissues.

So, those are the big-time decisions that an oyster faces: where to live, and when to eat. Sounds kind of familiar…

We want to hear from you! Add your question or comment.

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