Tag Archives: salt marsh

Four Ways (and more) That Salt Marshes Earn Their Keep

Episode 5: The True Value of a Salt Marsh

Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip- habitat 150IGOR chip- sedimentation 150IGOR chip- filtration 150IGOR chip- human appreciation 150

Much like David finds it hard to distill why the oysters that he studies are so intriguing, I often struggle to convey the charisma of the salt marshes and seagrass beds where I spend so much of my time. At least people like to eat oysters! It can be harder for people to find a connection with the plants that form so many of the critical habitats along our coast (unless of course people misunderstand the meaning of “In the Grass” and think I study a VERY different type of plant!). But even if it is not recognized, there is a connection between the salt marsh and our everyday lives. Like oyster reefs, salt marshes provide many benefits to society, particularly along the coast:

1. A place to live (for marine and terrestrial animals)

Periwinkle snails are among the many animals that make use of the salt marsh habitat.

Even if you’re one of those folks who find it hard to get excited about a bunch of plants, don’t tune out – the salt marsh is teeming with animals! Snails, fiddler crabs, mussels, grasshoppers, dragonflies, and snakes (!) are all critters that we encounter regularly when the tide is out. And there’s always a bit of an adrenaline rush when you see an alligator hauled out nearby. Even better, when the tide comes in, there are lots of animals that you and I (or at least, I) like to eat. Think blue crabs, mullet, and sea trout, for starters. Studies in Florida estimate that marshes provide up to nearly $7000 per acre for recreational fishing alone. Not bad.

2. A safer place to live (for people)

Although it’s generally frowned upon to build houses in the marsh (since it makes it hard for all those animals I just mentioned to live there), it’s a great idea to have lots of healthy marshes near your coastal property. Marshes can protect the coastline from waves and storms, leading to less damage in areas with marshes present. One estimate places the dollar value of coastal protection in the U.S. at over $8000 per hectare per year in reduced hurricane damages! Although here’s hoping that we don’t get an opportunity to test that particular benefit this year.

In addition to reducing the size and strength of waves, marshes also prevent coastal erosion. An unfortunate example of the role of marshes in erosion control came following the Deepwater Horizon oil spill – plants in areas of the marsh that were heavily oiled died, leading to greatly increased rates of erosion in those areas (Silliman et al. 2012). Although the benefit of marshes for reducing erosion and combating sea level rise has been recognized for a long time, there are not any good estimates for what this erosion control is worth in $$. Given expectations of sea level rise in the coming years, I think that the motivation to understand the conditions that lead to sediment accumulation in marshes will only get stronger.

3. Clean water (for animals and people)

Because marshes lie at the intersection of the land and the sea, they serve as a filter for things trying to move between the two. When it comes to run-off and pollution from the land, it’s a very good thing that they do. Simply having a marsh present can serve as an effective alternative to traditional waste treatment. Of course, the protection can go the other direction too – marshes played a critical role in keeping oil from the Deepwater Horizon oil spill from getting to higher elevations.

4. A place to graze (for livestock)

Support for livestock grazing is an important role of marshes in some areas, including the U.K. Although it’s not a benefit commonly associated with marshes in this area, the decaying fence posts that extend out into some areas of St. Joe Bay suggest that it wasn’t too long ago that marshes were used for a similar purpose here!

I could go on, but these and other benefits of marshes are described in greater detail in a recent review by Barbier and colleagues (which I referenced on this blog in May of 2011). Here is the table that they put together summarizing the monetary benefits that we derive from intact salt marshes:

Luckily for us, salt marshes keep working their magic even in the absence of accolades or appreciation. But greater appreciation is needed to help curb the decline of salt marshes around the world – estimated to be as much as 2% per year! We hope that this blog will help generate greater understanding and enthusiasm for the incredible coastal habitats that we are lucky enough to work in every day. Let us know how we’re doing!

In the next two weeks, we delve into a habitat that we have only occasionally covered: seagrass beds.  Next week we examine, with visiting researcher Dr. Peter MacReadie, seagrass beds’ role in fighting global climate change.  The week after that, we head to Bay Mouth Bar, one of the most ecologically unique places in the world.  Also, we’ll be look at the failure of the Apachicola Bay oyster reefs from a biological perspective.  Here are a few images of our visit to a Saint Joseph Bay seagrass bed and of Bay Mouth Bar at low tide, when you see all kinds of strange and interesting creatures:

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

Music in the piece by Kokenovem and Pitx

SciGirls Tallahassee (and Rebecca) Cope with Marsh Mud

Episode 3: Studying Nature Involves Visiting and Standing in Nature

In a couple of weeks we’ll dive right in and look at oyster reefs and their surprising value. In the weeks following, we’ll do the same with salt marshes, seagrass beds, and with the unique diversity of Bay Mouth Bar.  Right now, we hope you enjoy watching the WFSU/ Mag Lab SciGirls get their footing in the intertidal zone.
Rebecca Wilkerson WFSU-TV

SciGirls' mudy feetThe first question I was asked when I became involved in the In the Grass, On the Reef project was if I was afraid to go out in the field and get a little dirty. “Of course not!” was my response. I have always been a fan of the outdoors and love scalloping and kayaking, so of course I would love this. I guess I was expecting to be in the water more than anything. After all, we couldn’t really be going out into anything too messy, right?

The first few shoots I went on were great and went about how I expected they would. But after a few weeks we went to Wakulla Beach, where I discovered exactly why I was asked that particular question when I was hired. Not fully prepared for my experience that day, I had quite a time trying to walk through the mud without getting sucked in knee-deep and losing my shoes, causing others to slow down and get stuck as well while they were trying to help me out. After clawing my way out and finally escaping the mud, I walked on an oyster reef for the first time. While the mud was not nearly as bad at this point, I am a terribly clumsy person. Luckily, I was able to keep my footing and avoid falling on top of oyster shells.

Although it was exhausting, I still enjoyed my Wakulla Beach experience, as I’ve come to call it. It was definitely a learning experience for me and I loved being able to see the sunset over the reefs. I have yet to master the “quick, light steps” needed to defeat the mud, but I definitely have an appreciation for what our scientists, and many others, go through to set up experiments and collect their data. I also love that getting out in the water (and mud) are a part of my job, not to mention that we get to see some really cool things. Every shoot is a new experience and I notice more about the environment and the animals each time I go out.

And Also, the Animal Experience

Rob Diaz de Villegas WFSU-TV

Animals with claws suited to tearing through oyster shell can, unsurprisingly, injure you.

One thing we didn’t mention in the video above or in Rebecca’s post are the animals at the sites, which you definitely have to keep an eye out for.  Members of the Hughes and Kimbro labs have been pinched by blue crabs and have encountered the occasional snake in the marsh.  There are small sharks, the possibility of alligators, and the sting rays that we see and shuffle our feet to avoid stepping on and startling.  You keep an eye out for those knowing that they’re a potential danger, though not a pressing threat.  During last week’s shoots in Saint Augustine, however, events in the news had us paying serious attention to the smallest animals that are also the ones that attack us most relentlessly.  Our country is in the midst of perhaps its worst ever outbreak of West Nile virus.  Mosquitos are a fact of the coast.  During the day, there is usually enough of a breeze to keep them off you; but since the work we follow is tidally based, activities can occur before sunrise or after sunset, when mosquitos are at their worst.  Alligators may look scarier, but it pays to know what the most pressing threat is.

Listen to last Thursday’s Talk of the Nation on preventing West Nile.

Music in the video by grapes.  In the Grass, On the Reef theme music by Lydell Rawls.

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

WFSU SciGirls “In the Grass,” Talking Science

Episode 2: Talkin’ Science

In September we’ll tour our coastal ecosystems and learn why we love them.  These next couple of weeks, we’ll get a fresh set of eyes on Randall and David’s world of research and ecology as the WFSU/ Mag Lab SciGirls visit the FSU Coastal and Marine Lab.

Dr. Randall Hughes FSU Coastal & Marine Lab

Randall explains experiment to SciGirlsWhen you think of your summer vacations during middle school, what do you think of? The first thing that comes to my mind is HOT (it was south Georgia, after all), and the next thing is Duke. I realize that is somewhat sacrilegious for someone who went to UNC-Chapel Hill for undergrad (at least if you care anything about basketball). But I spent 4 summers as a student at the Duke University Talent Identification Program, better known as TIP, and my 3 weeks spent there each summer definitely stand out in my mind.

It sounds horrible to most people – 3 weeks during summer vacation spent taking an intensive course that would typically last a semester. Although we spent a lot of time in class and studying, in many ways it was like any other summer camp, with time spent goofing off with really interesting and fun classmates from all over the country. I even crossed paths with some of my fellow TIPsters in graduate school!

SciGirls trek into the marshSo what does this have to do with In the Grass, On the Reef? In many ways, nothing. But in some ways, everything. Because one of those summers I took Marine Biology at the Duke University Marine Lab in Beaufort, NC, and it was there that I fell in love with doing research on coastal systems (and did my first experiment on fiddler crabs!). Admittedly, it still took me a while to figure out how to turn that into a career, but I’m not sure that I would be where I am today were it not for 3 weeks during the summer before 8th grade.

Enter the SciGirls. For the last 4 summers, I’ve been thrilled to participate in the SciGirls summer camp run by WFSU and the National High Magnet Field Laboratory (aka, the Mag Lab), aimed at introducing middle and high school girls to careers in science. Although the SciGirls program is structured differently from the TIP program that I participated in, it provides me an opportunity to share my love of field research with some really amazing girls, and hopefully to plant the seed in their minds that they can turn their love of science into a career too.

This year, in addition to explaining my research to the SciGirls and getting their help collecting data, we talked about the importance of being able to communicate what you’re doing to others. It turns out that explaining research to non-scientists is not something that scientists are trained to do, and it doesn’t always come easy.  So we decided to start early with the SciGirls and see what happens!   As you can see from the video, they quickly grasped what they needed to do and were quite comfortable with the camera. There were some discrepancies among the observations, but hey, that’s why we take lots of data – you can’t always see the overall pattern when you’re only looking at a subset of the information!

The circle is complete. Randall was once the middle school student being led into a marsh for the first time, she is now the one leading middle school girls in. Might this fiddler crab have inspired someone into a career in research?

After a lunch break and a look at the results of our data collection, we headed to the field. This part of the day is always my favorite – watching the girls explore, answering their excited questions, helping them pick up their first fiddler crab, assuring them their shoes / clothes will come clean.  Even a short rainstorm didn’t dampen their enthusiasm. I would venture a guess that when these girls look back on their middle school summer vacation, their memories of SciGirls will be front and center.

For more on the SciGirls’ day at FSUCML, check out their blog.  And check back next week for video of their experiences in the grass (and mud)!

Music in the video by grapes.  In the Grass, On the Reef theme music by Lydell Rawls.

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

Video: Where the Land Meets the Sea

Episode 1: Where the Land Meets the Sea

Rob Diaz de Villegas WFSU-TV

This time around, everything is both familiar yet new.

On the new tiles, spat are glued on with a mixture used to repair boat hulls.

I recently went to Saint Augustine to document the second version of Dr. David Kimbro and Dr. Randall Hughes’ tile experiment.  The basic concept is this: attach a certain amount of oyster spat (larval oysters- basically little blobs in the process of growing and building shells) to tiles, leave them on or by oyster reefs and see how they grow, or if they are eaten.  I’ll let Randall and David explain the intricacies of the experiment when we post those videos in January.  Or, you could watch our coverage of that first experiment, conducted in the fall of 2010.  Watching that video and then watching our new videos on the experiment, you’ll notice that both the approach to the experiment and to the video coverage have evolved.  After the Kimbro lab spent so many long days scrambling to collect spat, The 2010 experiment didn’t succeed like they’d hoped.  Likewise, our communication of their research, and the importance of the ecology of intertidal ecosystems, didn’t quite succeed like I had hoped.   I like watching the old videos; I just don’t think they did what we wanted them to.  But you learn, and hopefully, you improve.

This time around, I was struck by how orderly everything was at the Whitney Lab as the oyster crew prepared their tiles.  No more scrambling out at low tide to collect oysters; they had hired someone to breed spat from oysters spanning the Eastern seaboard.  The current tile design and construction had been tested, and would withstand the elements.  Randall and David had learned lessons, and were efficiently implementing their new plan.  But what had I learned?

This attractive gastropod, seen in the video above, is a busycon snail wrapped around an atlantic moon snail that it just happens to be eating. Nature videos have a cast of human, animal, and plant characters.

Early last year, WFSU had a moment equivalent to that of the Hug-Bro labs’ realization that the glue on their initial tiles couldn’t withstand the waves at their sites.  The National Science Foundation had rejected our grant application to fund this project.  After a few months of following their studies and a couple dozen videos, a panel of reviewers let us know everything they thought we did wrong.  That was fun.

When Randall, David, Kim Kelling-Engstrom (WFSU’s Educational Services Director) and I decided to reapply for the grant, we needed a new narrative for what it was that we wanted to communicate.  What was our story?  If you watch our old videos, we’re very narrowly focused on experiments and field work.  There’s a lack of perspective on the impact of the ecosystems on our area, a lack of local color from the excellent locations we visit, and I kind of feel like we could have better captured what a day on a salt marsh or oyster reef was like.  The new application reflected more of the world around the reefs and marshes, and the people who need them.  If you’ve watched the video above, you may have figured that this time, our application was successful.

The red snapper being held by Ike Thomas, owner of My Way Seafood, was caught in 150 feet of water. Before reaching market size, younger snapper are one of many fish species that forage on oyster reefs.

I’m finding the new videos are more fun to put together.  We’re exploring the area more, talking to more people, and it’s easier to spot the animals we care about and get footage of them.  And with funding we have some extra staff helping on the blog and on shoots (like new associate producer Rebecca Wilkerson).  The upcoming videos are like the new tiles sitting in their cages off of Saint Augustine oyster reefs: they are the product of some hard won knowledge.  That experiment ends soon and they’ll see if they get the data they needed to meet their larger goals.  We, on the other hand, are just getting started, and we hope that you’ll keep joining us as we explore that area where the land meets the sea.

Over the next couple of weeks, we see the WFSU SciGirls visit the FSU Coastal & Marine Lab to learn about what Randall does: in the marsh, at the lab, and in front of the camera.  It gets a little messy.  In September, we go in the field with Randall and David onto oyster reefs and into seagrass beds and salt marshes.

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

Music in the piece was by Kokenovem and airtone.

Biodiversity and the Apalachicola: Why it’s Worth a Visit

Rob Diaz de Villegas WFSU-TV

Tune into WFSU-TV’s dimensions on Wednesday, February 15 at 7:30 PM/ ET to watch our paddling and wildlife watching EcoAdventure throughout the Apalachicola River system.

Zoom into the clusters of flags to see each site in more detail.
Island 3

This marsh island might be comprised of several genetically distinct cordgrass individuals, or just a few.

IGOR chip- human appreciation 150IGOR chip- biodiversity 150In composing and researching this post, I seem to have stumbled upon a diversity of biodiversity. In Randall Hughes’ salt marsh biodiversity study, you don’t always even physically see it.  Within a salt marsh, you might be looking at a variety of cordgrass individuals, or just one.  You wouldn’t know until you got the DNA results back from the lab.  That’s genetic diversity, the variation of genes within a species.  A little more obvious is the diversity of plant and animal life within a habitat: what other plants are mixed in with the cordgrass, what different predators are eating and terrorizing periwinkle snails, etc.  This species diversity is also crucial to a system’s health, and to the services it provides us. Continue reading

Dude, where’s my water?

Rob Diaz de Villegas WFSU-TV

IGOR chip- human appreciation 150

St. Joe Bay is really jumping in the summer. People are everywhere; scalloping, fishing, kayaking and snorkeling. The people are mostly gone in the autumn, as they head back to work and school, and the weather is a little cooler. With less people to scare them off, you see more blue crabs, stingrays, and sharks swimming closer to the shore. It’s my favorite time of year to get footage there. When winter rolls around, the only people out on the water either have to be because they’re working (like Randall and her crew), or they’re just hardcore ecowarriors. It can make for difficult paddling in the winter (though this December is much milder than last year, when we shot this footage).

Super-low tide in St. Joe Bay.

The difficulty doesn’t so much stem from the cold, though it can get cold (especially for a native Floridian who thinks Massachusetts beach water is too chilly in July). The real challenge is the wind and the tides. It makes for a surreal landscape.  It’s mostly devoid of living animals, at least on the surface, but that north wind does push some interesting seagrass bed denizens onto the marsh with the seagrass wrack.

As I noted earlier, it has been milder this year.  Hopefully that holds for our next few EcoAdventure shoots, which include trips down the Wacissa and St. Marks rivers.  And I’ve already started planning some of next year’s shoots as well, so stay tuned!

Dan and Debbie VanVleet, who we interviewed in the video, are the proprietors of Happy Ours Kayak and Canoe Outfitter.
The music in the video was by Bruce H. McCosar.

A long time in the making

Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip- biodiversity 150

As I mentioned in my last update, we have been working to set up a new marsh experiment in St. Joe Bay. The goal of the experiment is to see whether the genetic diversity of marsh cordgrass (Spartina alterniflora) affects how quickly or abundantly the plants grow, or influences the number of fiddler crabs, grasshoppers, snails, and other critters (like Ibis??) that call the plants home. But what is genetic diversity, exactly, and why do we think it may be important?


A flock of Ibis resting among our experimental marsh plots.

Spartina is a clonal plant, which means that a single “individual” or clone made up of many stems can dominate a large area (low diversity), or there can be lots of different individuals mixed together (high diversity). In our surveys of marshes in the northern Gulf of Mexico, we find that there can be as few as 1 and as many as 10 clones in an area of marsh about the size of a hula-hoop. You may notice that our experimental plots are about that same size, though we used irrigation tubing rather than actual hula-hoops (not as fun, but more practical and less expensive!). We’re testing whether the differences in genetic diversity (1 vs. 10 clones) that we see in natural marshes has any influence on the marsh community.

A single experimental plot of Spartina that is 1m in diameter.

But why genetic diversity? We know from experiments by other researchers that Spartina clones grown individually differ in height, how many stems they have, and other characteristics. These same plant traits affect the critters that live in and among the plants – for example, periwinkle snails preferentially climb on the tallest plants. Because different animals may be looking for different plant traits, then having greater diversity (genetic and trait) may lead to a greater number of animal species that live in that patch of marsh. Or, a single clone may be the “best”, leading to higher numbers of animals in lower diversity areas.


A view of the existing marsh behind our experiment.

As my title alludes, this experiment has taken a long time to come to fruition, in large part because it’s impossible to look at any 2 stems in a marsh and know for certain whether they’re the same individual or not. Unlike some clonal plants such as strawberries, where there are multiple berries connected by a single above-ground “runner”, Spartina has runners (aka, rhizomes) that connect stems of the same genetic individual under the ground, making it difficult to tell which stems are connected to which. We have 2 ways to get around this problem: (1) we use small snippets of DNA (analyzed in the lab) to tell clones apart, and (2) we start with single stems that we know are different clones and then grow them separately in the greenhouse until we have lots of stems of each different clone. It’s this latter part that has delayed this experiment – it has taken much tender loving care from Robyn over the last 2 years to get our Spartina clones to grow in the greenhouse to the point that we have enough of each clone (36 small flowerpots of each, to be exact) to plant in our experiment.


Emily and Robyn work to remove existing rhizome material from around the plot edges.

But plant we finally did! With lots of help from members of the Hughes and Kimbro labs, we got all the sand in the experimental plots sieved (to remove any existing root material) and all the plants in the ground the Thursday and Friday before Thanksgiving.


Team Hug-bro (Hughes and Kimbro) helping sieve sand!



Meagan and Randall get the easy job – planting the plants.

Now we get to wait and see (and take data) whether Spartina genetic diversity matters for the marsh plant or animal community. There won’t be any quick answers – the experiment will run for at least 2 years – but we’ll be sure to keep you up-to-date!

Randall’s research is funded by the National Science Foundation.

Tricks or Treats? And more on the effects of predators in marshes.

Dr. David Kimbro FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150Unlike most of the experiments that I’ve conducted up to this point in my career, the oyster experiment from this past summer does not contain a lot of data that can be analyzed quickly.

For example, predator effects on the survivorship of oysters can be quickly determined by simply counting the number of living as well as dead oysters and then by analyzing how survivorship changes across our 3 experimental treatments (i.e., cages with oysters only; cages with mudcrabs and oysters; cages with predators, mudcrabs, and oysters).  But this simple type of data tells us an incomplete story, because we are also interested in whether predators affected oyster filtration behavior and whether these behavioral effects led to differences in oyster traits (e.g., muscle mass) and ultimately the oyster’s influence on sediment characteristics.  If you recall, oyster filter-feeding and waste excretion can sometimes create sediment conditions that promote the removal of excess nitrogen from the system (i.e., denitrification)


As we are currently learning, getting the latter type of data after the experiment involves multiple time-consuming and tedious steps such as measuring the length and weight of each oyster, shucking it, scooping out and weighing the muscle tissue, drying the muscle tissue for 48 hours, and re-weighing the muscle tissue (read more about this process here).

After repeating all of these steps for nearly 4,000 individual oysters, we can subtract the wet and dry tissue masses to assess whether oysters were generally:

(a) all shell…“Yikes! Lot’s of predators around so I’ll devote all of my energy into thickening my shell”

(b) all meat…“Smells relaxing here, so why bother thickening my shell”

(c) or a mix of the two.

For the next two months, I will resemble a kid with a full Halloween bag of candy who cannot wait to look inside his bag to see whether it’s full of tricks (nonsensical data) or some tasty treats (nice clean and interesting data patterns)!  I’ll happily share the answer with you as soon as we get all the data in order.

Because of this delay, let’s explore some new research of mine that examined how predators affect prey traits in local marshes and why it matters.


There are two main ingredients to this story:

(a) tides (high versus low) dictate how often and how long predators like blue crabs visit marshes to feast on tasty prey.

(b) prey are not hapless victims; like you and me, they will avoid risky situations.

attach.msc1In Spartina alterniflora systems, periwinkle snails (prey) munch on dead plant material (detritus) lying on the ground or fungus growing on the Spartina leaves that hover over the ground.  Actually, according to Dr. B. Silliman at the University of Florida, these snails farm fungus by slicing open the Spartina leaves, which are then colonized by a fungal infection.  If snails fungal farm too much, then the plant will eventually become stressed and die.

So, I wondered if the fear of predators might control the intensity of this fungal farming and plant damage.

For instance, when the tide floods the marsh, snails race (pretty darn fast for a snail!) up plants to avoid the influx of hungry predators such as the blue crab.

After thinking about this image for a while, I wondered whether water full of predator cues might enhance fungal farming by causing the snail to remain away from the risky ground even during low tide.  Eventually, the snail would get hungry and need to eat, right?  Hence, my hypothesis about enhanced fungal farming due to predator cues.   I also wondered how much of this dynamic might depend on the schedule of the tide.

Before delving into how I answered these questions, you are probably wondering whether this nuance really matters in such a complicated world.  Fair enough, and so did I.

Addressing this doubt, I looked all around our coastline for any confirmatory signs and found that Spartina was less productive and had a lot more snail-farming scars along shorelines subjected to a diurnal tidal schedule (12 hours flood and 12 hours ebb each day) when compared to shorelines subjected to a mixed semidiurnal schedule (2 low tides interspersed among 2 high tides that are each 6 hours).  Even cooler, this pattern occurred despite there being equal numbers of snails and predators along both shorelines; obviously density or consumption effects are not driving this pattern.


Ok, with this observation, I felt more confident in carrying out a pretty crazy laboratory experiment to see if my hypothesis might provide an explanation.


Enter Bobby Henderson.  This skilled wizard constructed a system that allowed me to manipulate tides within tanks and therefore mimic natural marsh systems; well, at least more so than does a system of buckets that ignore the tides.


Within each row of tide (blue or red), I randomly assigned each tank a particular predator treatment.  These treatments allowed me to dictate not only whether predators were present but whether they could consume & frighten snails versus just frightening them:

-Spartina only

-Spartina and snails

-Spartina, snails, and crown conch (predator)

-Spartina, snails, blue crab (predator)

-Spartina, snails, crown conch and blue crab (multiple predators)

-Spartina, snails, cue of crown conch (non-lethal predator)

-Spartina, snails, cue of blue crab (non-lethal predator)

-Spartina, snails, cues of crown conch and blue crab (non-lethal multiple predators)

attach.msc6After a few weeks, I found out the following:

(1) Predators caused snails to ascend Spartina regardless of tide and predator identity.  In other words, any predator cue and tide did the job in terms of scaring the dickens out of snails.

(2) Regardless of tide, blue crabs ate a lot more snails than did the slow moving crown conch and together they ate even more.  This ain’t rocket science!

(3) In this refuge from the predators, snails in the diurnal tide wacked away at the marsh while snails in the mixed tide had no effect on the marsh.


Whoa…the tidal schedule totally dictated whether predator cues indirectly benefitted or harmed Spartina through their direct effects on snail predator-avoidance and farming behavior.  And, this matches the observations in nature… pretty cool story about how the same assemblage of predator and prey can dance to a different tune when put in a slightly different environment.  This study will soon be published in the journal Ecology.  But until its publication, you can check out a more formal summary of this study here.

If this sort of thing happens just along a relatively small portion of our coastline, I can’t wait to see what comes of our data from the oyster experiment, which was conducted over 1,000 km.

Till next time,


David’s research is funded by the National Science Foundation.

Are two friends better than one?

Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip- biodiversity 150


Sand fiddler crab.

This summer we’ve been conducting an experiment on our new deck to look at the effects of fiddler crabs and ribbed mussels on Spartina alterniflora (smooth cordgrass).

Past studies by Dr. Mark Bertness have shown that crabs and mussels by themselves can have positive effects on plant growth – most likely because crabs can reduce the stress of low oxygen in the sediments by building their burrows, and mussels can add nutrients to the sediments.

Fig. 3 from Bertness 1984, Ecology 65: 1794-1807

Figure 3 from Mark Bertness’s 1984 Ecology study illustrating the positive effects of mussel presence (white bars) on Spartina

Table 3 from Bertness 1985, Ecology 66: 1042-1055

Table 3 from Mark Bertness’s 1985 Ecology study. Fiddler removal has a negative effect on Spartina in the marsh flat, but not the marsh edge.

Although both fiddlers and mussels occur together in the field, no studies have looked at how the combination affects the plants. Are the positive effects of each species by itself doubled? Or are they redundant with each other? Do crabs somehow reduce the positive effect of mussels, or vice-versa? How many crabs or mussels do you need to get a positive effect on Spartina? These are some of the questions that we hope to answer with our experiment.


Our new deck at FSUCML.

But first, we had to get everything set up. There were several long and hot days of shoveling sand into our “mesocosms” (10 gallon buckets) – many thanks to Robyn, Chris, Althea, and all the others who took care of that task! Then there was another day spent transplanting the Spartina.


Chris, Randall, and Robyn work to transplant Spartina from the greenhouse to the mesocosms.

Finally, it was time to add the fiddlers and mussels, and everything began!


Mussels nestled among the Spartina stems in one of our experimental mesocosms

Althea and Chris have been leading the charge on this experiment, and they’ve spent a lot of time getting to know (and identify) the fiddler crabs. All in all, a pretty fun study organism!


Althea working to identify fiddler crab species.

We’ll continue the experiment another month and then measure the height and density of the plants in each treatment to see if there are any differences. Once this experiment is complete, we’ll set up a separate one asking somewhat of the converse question – are two enemies (periwinkle snails and grasshoppers) worse than one? We’ll keep you posted.

Randall’s research is funded by the National Science Foundation.
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The End of an Era

Dr. Randall Hughes FSU Coastal & Marine Lab

Randall examines an experiment cage as Robyn looks on.

IGOR chip- biodiversity 150Calling a one year experiment an “era” is probably a bit of an over-statement, but the end of our snail field experiment definitely feels significant. Especially for Robyn, who has traveled to St. Joe Bay at least once a week for the past year to count snails and take other data. And also for the Webbs, who were kind enough to let us put cages up in the marsh right in front of their house and then proceed to show up to check on them at odd hours for the last year!  And finally for this blog, because the beginning of the snail experiment was the first thing we documented last summer when we started this project with WFSU.  It’s nice to come full circle.

So why, you may wonder, are we ending things now? Is it simply because one year is a nice round number? Not really, though there is some satisfaction in that. The actual reasons include:

(1) The experiment has now run long enough that if snails were going to have an effect on cordgrass, we should have seen it by now. (At least based on prior studies with these same species in GA.)
(2) In fact, we have seen an effect of periwinkle snails, and in some cages there are very few plants left alive for us to count! (And lots of zeros are generally not good when it comes to data analysis.)
(3) Perhaps the most important reason to end things now:  it’s become increasingly difficult in some cages to differentiate the cordgrass that we transplanted from the cordgrass that is growing there naturally. Being able to tell them apart is critical in order for our data to be accurate.
(4) The results of the experiment have been consistent over the last several months, which increases my confidence that they are “real” and not simply some fluke of timing or season.

And what are the results? As I mentioned above, snails can have a really dramatic effect on cordgrass, most noticeably when our experimental transplant is the only game in town (i.e., all the neighboring plants have been removed). And not surprisingly, cordgrass does just fine in the absence of snails and neighbors – they’re not competing with anyone or being eaten!


Snails also have a pretty strong effect on the experimental cordgrass transplant (compared to when no snails are present) when all of its neighbors are cordgrass.


Most interestingly, snails do not have a big effect on the experimental cordgrass transplant when some of the neighboring plants are needlerush.


This result is consistent with some of the patterns we’ve observed in natural marshes, where cordgrass growing with needlerush neighbors is taller and looks “healthier” than nearby cordgrass growing without needlerush.

Having decimated the plants in the cage, the snails move towards the tallest structure they can reach- a PVC pipe.

But why? Those snails are pretty smart. They generally prefer to climb on the tallest plant around, because it gives them a better refuge at high tide when their predators move into the marsh. (We’ve shown this refuge effect in the lab – fewer snails get eaten by blue crabs  in tanks with some tall plants  than in tanks with all short plants.) Needlerush is almost always taller than cordgrass in the marshes around here, so this preference for tall plants means that snails spend less time on cordgrass when needlerush is around. And finally, less time on cordgrass means less time grazing on cordgrass, so the cordgrass growing with needlerush experiences less grazing pressure.

These results – consumer (snail) effects on cordgrass are lower when cordgrass grows mixed with needlerush – are consistent with theory on the effect of diversity, even though in this case we’re only talking about a “diversity” of 2 plant species.  And they could be important in the recovery or restoration of marsh areas where snails are causing a large reduction in cordgrass biomass.

The one thing we still don’t know with certainty – how do the snails determine which plant is taller??

I guess that’s the beauty of this job, in that there are always more questions to answer.

Randall’s research is funded by the National Science Foundation.

The new documentary, In the Grass, On the Reef: Testing the Ecology of Fear had a segment on the snail experiment.  Watch the full program here.  You can also read Randall’s post from the beginning of the experiment, and watch a video, here.

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