Tag Archives: gulf of mexico

RiverTrekkers climb into Means Creek, named for biologist Bruce Means.

Video: RiverTrek 2012 Days 1 & 2

Rob Diaz de Villegas WFSU-TV

Part 2 of our RiverTrek adventure is now live. You can watch it here.

RiverTrekkers climb into Means Creek, named for biologist Bruce Means.

IGOR chip- filtration 150The web version of the video, which you see above, has some shots of our impromptu spelunking expedition by Means Creek that were not in the air version.  I was waiting on permission to show our cave adventure, which was in a part of Torreya State Park that we were told will be opened to the public at some point in the future.  I got that permission after last week’s Dimensions had been completed.  You may notice that, for a video about a kayak trip, we spend a lot of time in caves, bushwhacking in the woods, or climbing up bluffs.  None of our off-river excursions were in lands open to the public, but were instead near parklands that were (Means Creek in Torreya and Alum Bluff on The Nature Conservancy’s Apalachicola Bluffs and Ravines Preserve, near the Garden of Eden Trail).  With those parks in the northern stretch of the river and the Apalachicola Wildlife and Environmental Area in the south, there are ample opportunities to explore the areas adjacent to the river.  Those protected lands are valuable for their ecotourism potential, but they have a indirect value when it comes to the water in the river, in Apalachicola Bay, and into the Gulf of Mexico.

It has to do with clean (or cleaner, anyway) water.  I wrote last week about the Army Corps of Engineers visit to Apalachicola Bay, and the meeting during which various presenters made their case for the why the river needed more water than has been flowing through the Woodruff Dam.  One presentation that left an impression was that of Dr. Felicia Coleman, Director of the FSU Coastal and Marine Lab.  She was showing how the water flowing from the Apalachicola River had positive effects beyond the bay, and she made an interesting contrast.  She was comparing the “green river” plumes from both the Apalachicola and Mississippi Rivers, the two largest North American sources of freshwater in the Gulf.  Along with the fresh water, they contribute chlorophyll and other nutrients.  There is a striking difference in what each river is putting into the Gulf.

“The two sources are quite different, because one is man made, agricultural… excess nutrients are falling into the Gulf” Dr. Coleman said, referring to the Mississippi, “and the other is a natural nutrient base that’s coming into the bay,” referring to the Apalachicola.  The Mississippi River drains 41% of the continental United States, along with considerable nitrogen and phosphorus such as are found in concentrated fertilizers typically used to grow crops and and keep lawns green.  The areas at the mouth of the Mississippi have been heavily developed, so there aren’t the kinds of coastal ecosystems that would filter these nutrients (though as David Kimbro pointed out to me, the sheer volume of runoff from the Mississippi is greater than what these coastal ecosystems could filter).  All of that nitrogen and phosphorous was of course meant to make plants grow, and a farmer can control how fertilizer is applied to get crops to grow how they want and to maximize their yield.  When it runs off of farms and lawns and into the water, you can’t control what plants grow and how fast.  If phytoplankton gets a super dose of nitrogen, its growth can become unchecked and it can suck the oxygen out of water.  Dr. Coleman estimated that the dead zone off of the Mississippi is about the size of New Jersey.

Shrimp boats in Apalachicola, at the very end of RiverTrek 2012.

So, that’s me taking a hike on Alum Bluff and trying to make it about the oysters in the bay.  But there is a connection to the bay, and as Felicia Coleman illustrated, beyond the bay and into the Gulf.  Gag and red grouper are commercially important fish that are caught in waters that are about 60 feet deep.  They spawn when the green river plume is at its seasonal peak (the flow of the river is not constant).  Dr. Coleman presented a map that showed the greatest concentration of grouper spawning happened within that plume.    So the water flow, which is at an all time low (since people have started measuring it), is crucial to that fishery as well as to the shrimp, crab, and oyster fisheries of the bay.  “If you look at rivers around the world that have had intense fresh water withdrawals,” Dr. Coleman said, “There have been some of the most spectacular fishery failures that we know about, in a global sense.”

Riverlinks

I’m not the only one publishing blog posts on RiverTrek 2012.  My fellow paddler (and author) Doug Alderson wrote this post for his Visit Tallahassee blog.

The Army Corps of Engineers is updating the Apalachicola/ Chattahoochee/ Flint Master Water Control Manual, and they are taking public input.  You can let your voice be heard here.

Stay tuned for Part II of the RiverTrek Adventure on Wednesday November 14 at 7:30 PM/ ET as we complete our journey to the bay.

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Shells, Buried History, and the Apalachee Coastal Connection

Rob Diaz de Villegas WFSU-TV

IGOR chip- human appreciation 150IGOR chip- habitat 150Have you ever found oyster shells in the dirt of your backyard?  If you have and you live in Tallahassee’s Myers Park neighborhood, then you might be looking at the remains of a powerful native village that rose to prominence over 500 years ago.

Missions San Luis scallop-oysterI was on a shoot for the first episode of our newest program, Florida Footprints. We were at the Florida Museum of History interviewing KC Smith about her involvement in the excavation of the Hernando de Soto winter encampment in 1987.  Back then the city was abuzz about the artifacts being found so widely dispersed off of the appropriately  named Apalachee Parkway.  They had likely discovered the central Apalachee village of Anhaica, where de Soto spent the first winter of his North American expedition.  People were finding piles of artifacts in their backyards.  After the interview, I asked Smith how deep I’d have to dig to see if I had artifacts in my yard.

“Do you have oyster shells in your yard?”  she asked.

Oyster shells?  Evidently, these were the indicator of an Apalachee site.  No one is sure what the shells were used for, though she believes they were used as small dishes.  This is consistent with the interpretation in the photo above, taken at Mission San Luis, of scallop shells storing food stuffs.  As Dr. Bonnie McEwan, Director of Archeology at the Mission, points out, “… Apalachees undoubtedly harvested and ate a lot of oysters when they were near the coast.  But because there was no way to preserve them, they didn’t carry them.”  So they weren’t eating oysters in Anhaica, so far from the coast, they were just bringing the shells back.  Of all the shells they carried with them from Apalachee Bay, the most valuable belonged to a resident of the oyster reef, and to all of the intertidal habitats we follow: The lightning whelk (Busycon contrarium).

whelk-black drink vesselMuch like our coastal shellfish are economically important today, lightning whelk shells were of particular value for the Apalachee.  This had less to do with their meat than it did the size and shape of their shell.  Whelks are predatory snails that get quite large, with an elegant sinistral (left hand) curve.  I imagine that it’s the impressive appearance of a mature Busycon that led to their use in ritual life.  “The outer shells with the columellae removed were used as dippers or cups,” Dr. McEwan said, “and these were used in Black Drink ceremonies. As we discussed, Black Drink was an emetic tea brewed from yaupon holly (Ilex vomitoria) leaves.”  Anyone familiar with the effects of holly knows where the vomitoria species name comes from.  The regurgitation caused by the Black Drink was a form of ritual purification, and was a central component of the ceremonies held in preparation for the fierce and occasionally deadly Apalachee ball game (the ball game is the focus of my segment in Florida Footprints).  In the second photo to the right, you can see an interpretation of what a decorated Black Drink vessel looked like.

And whelks had value far outside of our area.  The Apalachee were part of the Mississippian culture, and with it part of a trade network that stretched to the Great Lakes.  Whelks with chemical signatures identifying them as from the Gulf have been found in Arkansas and Illinois.  “In exchange for the shells,” Dr. McEwan said, “the Apalachees received artifacts made from ‘exotic’ or non-local materials such as copper, lead, mica, and steatite, all of which were found associated with burials at the Apalachees’ Mississippian capital– Lake Jackson.”  Lake Jackson was capital of the Apalachee until about 1500.  Judging by the materials for which they were traded, whelks were highly valued.  Dr. McEwan elaborates on this. “In general, most of these items are found in association with burials of high status individuals throughout the Mississippian world since they conferred prestige.”

Here is a video of a lightning whelk roaming nearby St. Joseph Bay:

Since we’ve started the In the Grass, On the Reef project, one of the things that has interested me most is how the many cultures of this area, spanning thousands of years, have connected with the Gulf.  I’ve enjoyed the illumination I’ve received on this little sidebar to the segment I produced.  The next few episodes of Florida Footprints will move forward in time to cover our history since the Spanish arrived.  Hopefully, we will later also look in the other direction at the people who left oyster middens on St. Vincent Island or to the Aucilla River, where the remains of the first Floridians and the mastodons they hunted continue to be found.

My co-producers on this episode are Mike Plummer and Suzanne Smith.  Suzanne is covering the de Soto excavation and the discovery of Anhaica.  Mike is looking at the Spanish mission period in our area.

Watch a preview of Florida Footprints: Once Upon Anhaica:

Photo feature: Oyster Love

From the FSU Coastal & Marine Lab

IGOR chip- human appreciation 150What’s not to love about oysters? They clean the water, they’re delicious, and they have surprising economic value. Members of the Kimbro Lab found this unique oyster, which itself seems very loving, on one of their study sites. “Now I’ve seen a lot of weird-shaped oysters,” says lab tech Tanya Rogers,” but never one quite this perfect. I took it on a photoshoot this evening for some nice background and lighting.”

A long time in the making

Dr. Randall Hughes FSU Coastal & Marine Lab

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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?

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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.

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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.

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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.

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

 

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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)

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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.

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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.

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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.

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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.

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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.

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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

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

The Path Less Paddled

Take a photo tour of the Forgotten Coast segment of the Florida Circumnavigational Saltwater Paddling Trail.  Watch a video on the trail on Wednesday, September 14 at 7:30 PM/ ET on WFSU-TV.

Rob Diaz de Villegas WFSU-TV

IGOR chip- human appreciation 150IGOR chip- habitat 150IGOR chip- gastronomy 150It all happened in about five minutes. The gull swooped down and grabbed a soft-shell blue crab about half its size, abandoned it to a swarm of small fish, whose activity may or may not have attracted a shark coming in from Apalachicola Bay.  I was standing at Sugar Hill, a beach campsite in the St. George Island State Park, the last campsite along the Forgotten Coast segment of the Florida Circumnavigational Saltwater Paddling Trail.  You can see this video on tomorrow’s dimensions.

(watch a video on the making of a blue crab molting its shell)

Were a kayaker to try to make the five or six day paddle from Cape San Blas to St. George Island, they would likely see a few of these little dramas play out.  As Doug Alderson (Paddling Trails Coordinator for the Florida Office of Greenways and Trails)  says in the piece, it’s one of the wildest stretches of the statewide trail.  That means it has a lot of nice scenery of coastal habitats.  Much more interesting, though, is that they are functioning habitats.

Predatory snails on Sugar Hill Beach at St. George Island State Park

Large predatory snails congregating on a tree stump at Sugar Hill camp site.

For instance, Doug loves to catch redfish when he camps on St. George; and they’re always there for him.  But why are these fish so abundant in Apalachicola Bay?  The answer is in those tasty oysters that put the name Apalachicola on the map.  Oyster reefs are a refuge for all kinds of animals like stone crabs, blue crabs, and various predatory snails and small fish.  It’s an all you can eat buffet for larger fish looking for those small fish and little mud crabs.  The action I described above happened by a seagrass bed not far offshore.  Those beds thrive in water that oysters filter clean, and so they provide another habitat for marine life in the bay.  I ate Apalachicola oysters for years without realizing just how much they give, and give, and give…

Rob and Debbie by kayak

Rob photographs small fish and crabs that Debbie scooped out of St. Joe Bay.

At the other end of the trail, In Saint Joseph Bay, we caught up with Dan and Debbie VanVleet of Happy Ours Kayak and Canoe Outpost.  When WFSU first started the In the Grass, On the Reef project, we rented our kayaks from Dan and Debbie.  Debbie’s been wanting to take us snorkeling for a while, to get some video of some of the critters living in seagrass beds in St. Joe Bay.  Kayaking over the shallow waters in the bay, you can see the turtlegrass from where you’re sitting, as well as rays, horseshoe crabs, and snails making their way about the sandy bottom.  To see the creatures living in the seagrass beds, you have to get out of the kayak.  This is where you have to be careful.

It is illegal to remove shells from St. Joseph BayWhen I say be careful, I’m not just talking about your safety, though you should shuffle your feet to alert stingrays that you’re coming, or if you kayak to St. Vincent Island, definitely stay out of the way of charging boars.  You also have to be careful with these habitats, and the marine life within them.  Dan and Debbie (and local law enforcement) are very big on people not taking seashells out of the bay.  Taking a bunch of whelks and crown conchs out of the bay means taking out critical predators, removing a top layer in the local food web.  And, as the sign implies, even a dead shell has a role to play (any hermit crab would agree).  It’s called the “leave no trace” approach, and there are tips on how to best accomplish this on the trail website.  There are also safety tips and maps.  If you’re attempting anything more than a day trip along this trail, it’s a pretty comprehensive resource.

Doug has put a lot of work into mapping the trail- it took three years- and assembling resources so that people could best enjoy it.  You can hear the love he has for paddling when he reads from his book, Wild Florida Waters.  You’ll hear a couple of passages in the show tomorrow.  Even hearing him read about paddling in a strong wind kind of gets me excited about going out again.  It reminds me of paddling to safety in St. Joe Bay after a sudden thunderstorm erupts, or paddling in December when the cold water numbed my hands.  It’s not as predicable a form of recreation as visiting a beach resort.  But it’s never boring.

Doug and Josh

Thanks to Doug (L) for talking to us, and Park Ranger Josh Hodson for driving us around St. George Island State Park.

Dan and Debbie from Happy Ours

Thanks to Debbie and Dan for taking us out.

Have fun out there.  And share your stories with us!  Click on the Ecotourism North Florida link above if you have an eco-adventure you’d like to see us cover.

Kayaking, anyone?

Rob Diaz de Villegas WFSU-TV

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Here’s a vacation idea for you.

If you had the time, didn’t mind camping for months on end, and were physically up to paddling fifteen hundred miles, you could paddle around the entire state of Florida using trails mapped out by Doug Alderson.  He coordinates the Florida Circumnavigational Paddling Trail for the Florida Department of Environmental Protection (Visit the trail’s web site).  You would pass by major urban centers like Tampa and Miami.  You would make your way through the entirety of the Florida keys.  And you would see a lot of amazing coastal habitats.

Ready to go?

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The Forgotten Coast segment of the trail starts in St. Joseph Peninsula State Park.

I’m guessing the vast majority of people reading this are saying no, though we would certainly want to hear from you if you were doing this.  Luckily, the trail breaks down into twenty six segments, and over one hundred individual day trips.  The one I’m interested in is Segment 4: The Forgotten Coast.  It takes you through some of my favorite places.  St. Joseph Bay has clear water and lively seagrass beds and salt marshes.  Many of St. Vincent Island’s most interesting animals aren’t aquatic, but if you look over as you paddle past you might see wild hogs running or even one of those elusive red wolves (not likely, but it doesn’t hurt to look).  Once you pass there, you could choose to either go along St. George Island or stick to the mainland and pass by Apalachicola, where you can try to find a place to land your kayak while you pick up some oysters.

We’ll be kayaking part of this trail for September 14 episode, and talking to Mr. Alderson about it.  Have any of you done this?  Are any of you attempting this, or any section of it, any time in the next month?  We want to know.  We want to see your photos.  We want to watch your videos. Leave a comment below, with links to any videos or photos if you like.  If you’ll be out that way in the next couple of weeks, we may want to interview you.

Leave your comments!

And we want to keep hearing from you.  If you have any ideas for stories we might do related to coastal ecotourism, leave a comment on our Ecotourism North Florida page.

 

Are two friends better than one?

Dr. Randall Hughes FSU Coastal & Marine Lab

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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.

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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.

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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!

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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!

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

The End of an Era

Dr. Randall Hughes FSU Coastal & Marine Lab
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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!

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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.

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

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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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Horse Conchs Rule the Seagrass Bed

In the Grass, On the Reef: Testing the Ecology of Fear

Premieres on WFSU-TV Wednesday, June 29 at 7:30 PM, 6:30 CT.  In high definition where available.

Rob Diaz de Villegas WFSU-TV

IGOR_chip_predators_NCE_100This clip is a short segment on one of the predators featured in this program: the horse conch.  It’s practically an ecosystem onto itself, as you can see in the video’s poster frame above.  Barnacles, crepidula, bryozoans, and other marine creatures that affix themselves to hard surfaces settle on its shell.  In the video you’ll see its bright orange body as it roams the seagrass beds of the Forgotten Coast.  And you’ll see it eat another large predatory snail, the lightning whelk.

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