Category Archives: On the Sand

TulipMurex

Predator Diversity Loss and Bay Mouth Bar: The Next Stage

David and Randall’s NSF funded oyster study looks to understand how predators control oyster eating animals such as mud crabs and crown conchs. But this dynamic isn’t exclusive to oyster reefs. They are also investigating how predators might help maintain salt marshes and seagrass beds. In their seagrass bed studies, they have focused on a system loaded with predators: Bay Mouth Bar.
Tanya Rogers FSU Coastal & Marine Lab

Tanya RogersThe very first time I drove from Tallahassee to the FSU Coastal & Marine Lab I saw a black bear crossing the Crawfordville highway. No joke. This was in June of 2010, and I had just driven 5 days and 2800 miles from San Francisco to the Florida panhandle to take up my new job on the Gulf Coast. I had just finished college in Washington state, and I had never before been to the Southeast. What sort of wild place had I ended up in?

IGOR chip_ predators_NCE 150IGOR chip- biodiversity 150A very wild and unique one it turns out, and one I’ve come to know better working for the past few years as a research technician for Dr. David Kimbro in the fascinating coastal habitats of this region. Primarily I’ve been traipsing around oysters reefs across the state for the collaborative biogeographic oyster study (now drawing to a close), but for the past year or so I’ve also been managing our side project in the Bay Mouth Bar system, a sandbar and seagrass bed near the FSU Marine Lab. Bay Mouth Bar is a naturalist’s playground filled with surprises and an astonishing diversity of marine creatures that never ceases to amaze me. It is also a unique study system with an intriguing history out of which we can begin asking many interesting questions. This coming fall I’m excited to be starting as Dr. Kimbro’s Ph.D. student at Northeastern University, and for part of my dissertation I’ve decided to conduct some new experimental research this spring and summer out on Bay Mouth Bar.

Horse conch consuming a banded tulip snail on Bay Mouth Bar.

A horse conch in Tanya's experiment consuming a banded tulip snail.

Bay Mouth Bar is known for its especially diverse assemblage of large predatory snails, which the ecologist Robert T. Paine conducted a study of in the late 1950′s. In 2010, we began surveying the snail community on the bar, interested in what changes might have occurred in the 50 years since Paine’s time, a period during which very little research had been done in this system. I began synthesizing some of the data we’ve gathered, as well as talking to some of the long-term residents of the area. So what has changed on Bay Mouth Bar since the 1950’s? A number of things in fact:

  • Of the 6 most common predatory snail species, 2 are no longer present: the true tulip and the murex snail.
  • The number of specialist snails (like the murex, which only eats clams) has declined relative to the number of generalist snails (those that eat a variety of prey, like the banded tulip).
  • There has been a drastic reduction in the overall area of the bar and changes in the coverage seagrass, specifically the loss of large meadows turtle grass (Thalassia testudinum).
  • Surface dwelling bivalves (e.g. scallops, cockles), once enormously abundant, are now very rare.
True Tulip and murex Snails (no longer found at Bay Mouth Bar)

The two main snail species no longer found at Bay Mouth Bar, true tulip (The larger snail on the left, eating a banded tulip) and murex (right). The true tulip was, along with the horse conch, a top predator of the ecosystem, while the murex is a specialist snail, eating only clams.

Why is this interesting? Worldwide, we know that species diversity is declining as a result of human activities, that specialists are being increasingly replaced by generalists, and that consumer and predator species often face a disproportionate risk of local extinction. So what are the consequences of realistic losses and changes to biodiversity? Is having a diversity of predators beneficial (e.g. both horse conchs and true tulips) to an ecosystem as a whole? Do some species matter more than others? And how do the effects of predators depend on the type of habitat they’re in, given that habitats (like seagrasses) are also changing in response to the environmental changes? These are some of the questions I’m hoping to address in Bay Mouth Bar system, in which we have documented historical changes in predator diversity.

Tethered community in Tanya's Bay Mouth Bar experiment

One of communities in Tanya's experiment. At the center are top predators reflecting either the current assemblage (a horse conch alone) or the historic assemblage (the horse conch and true tulip). The predators are tethered to posts and given enough line to reach the lower level predatory snails (murex, lightning whelks, banded tulips, and Busycon spiratum) on the outside. Those snails have enough line to get out of the large predator's reach and forage for food.

This past week, I set up an experiment featuring a menagerie of snails tethered in different assemblages across Bay Mouth Bar. Some assemblages mimic the current assemblage, whereas others mimic the assemblage found on the bar during Paine’s time. These historical assemblages include the snail species no longer found there, which I collected from other locations where they are still abundant. Some assemblages have top predators (e.g. horse conchs) whereas others do not. Some are in turtle grass, others are in shoal grass. We’ll see how, over the course of the summer, these different assemblages affect the prey community (clams, mussels, small snails) and other elements of seagrass ecosystem functioning.

Music in the piece by Donnie Drost.  Theme by Lydell Rawls.

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

 

IMG_0983a

Notes From the Field: Leashing Your Clams

Tanya Rogers FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150It’s a problem commonly faced by field biologists: You want to put some particular critters out in the field in various places, but how do you keep them from getting swept away or wandering off too far, and how do you ever find them again later to see how they did? Behold the tether! So long as tethers are designed not to interfere too much with the animals’ natural behavior (walking around, burrowing, etc), leashing them to a fixed object is generally a good way to relocate them (provided you study something like crabs or snails and not lions or bald eagles). The other fun benefit of tethering marine invertebrates: you can take them for walks (albeit slow ones).

I recently conducted an experiment in which I put tethered baby clams (sunray venus and quahog, about 12 mm long) out on Bay Mouth Bar to see how their growth, survivorship, and burial depth was affected by (1) their location on the bar (NE, SW, SE, NW) and (2) the type of habitat the clams were in (sand, shoal grass, turtle grass). I checked on the clams a month later: some were still alive and growing, others were dead with clues indicating their likely cause of demise – gaping shell with no damage (stress), cracked shell (eaten by crab), drill hole in shell (eaten by predatory snail). My preliminary analysis suggests that survivorship and causes of death varied between habitat types. Next I hope to do a similar sort of study with tethered snails on Bay Mouth Bar.

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

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

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Notes From the Field: Horse Conch Honeymoon

Rob Diaz de Villegas WFSU-TV

When we started doing Notes From the Field, the intention was for the researchers and their techs and students to write about interesting things they saw or did while conducting their studies.  But I’m sneaking one in.  A couple of weeks ago I went out to Bay Mouth Bar with David Kimbro and his crew for their monthly sampling of gastropods and bivalves.  Horse conchs were plentiful during the summer months, but as the temperature drops they leave for deeper and warmer waters.  WFSU videographer Dan Peeri and I walked around getting shots of dead turtlegrass, a sign of seasonal change.  Oystercatchers were eating sea urchins; how close would they and the other birds let us get?

It was an interesting but quiet day when we heard a shout at the west end of the bar, facing the open Gulf.  Hanna Garland, newly returned from her graduate study on the crown conch problem south of Saint Augustine, seemed to have found something interesting.  Whenever there’s yelling at Bay Mouth Bar, there’s good footage to be found.  Hanna had found a pair of horse conchs mating.  There were several of the football sized orange snails on this side of the bar, including a second coupled pair.  It seems that they hadn’t quite made it to deeper waters, but were perhaps on the way.  And the behavior we observed got my imagination going.  Do they mate before heading on, laying their eggs in deeper waters?  Is that why they leave in the winter, leaving the door open for increased lightning whelk activity?  We can’t say that based on things we saw one day.  But that is one of the wonderful things about visiting wild habitats: seeing animals behave in different ways and getting glimpses into why things happen the way they do (even if careful study ends up providing an alternate narrative).

Horse conchs make an appearance in my EcoAdventures segment on the Leave No Trace principles on tonight’s episode of Dimensions, at 7:30 PM/ ET.  Part of visiting wild places and witnessing interesting behavior is not influencing it with your own behavior. We go over best practices for not disturbing a habitat and its inhabitants.  And for those who haven’t gotten enough Apalachicola River video, our State Parks One Tank Adventure segment tonight is on Torreya State Park.  Also, you can check out our new Apalachicola River and Bay Basin page, under the EcoAdventures North Florida menu.  From there you’ll have access to all of our videos on the basin (beyond the river and the bay) and play with our interactive photo map.

We want to hear from you! Who has seen any interesting animal behavior based on seasonal change? Add your question or comment.

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

P1030522

Backyard Ecology (Plus new video on Bay Mouth Bar)

Episode 7: Where Everything is Hungry

It’s always a good shoot day at Bay Mouth Bar as every animal seems to be eating every other animal.  Oyster reefs, salt marshes, and seagrass beds- the habitats we’ve covered over the last three weeks- reward those who take the time to look closely.  At Bay Mouth Bar, everything is all out in the open.  For a limited time, anyway…
Dr. David Kimbro FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150IGOR chip- filtration 150Like most kids, I spent a lot of my formative years in the backyard practicing how to throw the game-winning touch down pass, to shoot the game winning three-pointer, and to sink the formidably long putt.  Although my backyard facilities obviously didn’t propel me into the NFL, NBA, or PGA, they never closed, required no admission fee from my pockets (thanks Mom and Dad!), and were only a few steps away.

Now that I’m striving to be an ecologist at Florida State University, I’m feeling pretty darn lucky about my backyard again. Instead of spending tons of time flying, boating, and driving to far away exotic places, I can use a kayak and ten minutes of David-power to access some amazing habitats right here along the Forgotten Coast.

Part of this coastal backyard was first intellectually groomed by one of the more famous and pioneering scientists of modern-day ecology, Dr. Robert Paine. Five decades ago, Dr. Paine noticed that the tip of Alligator Point sticks out of the water for a few hours at low tide. Of course, this only happens when the tides get really low, which happens about 5 days every month. But when the tip of Alligator Point (which is locally called Bay Mouth Bar) did emerge from the sea each month, Dr. Paine saw tons of large carnivorous snails slithering around a mixture of mud and seagrass. When I first saw this place, my eyeballs bulged out at the site of snails as large as footballs!

Fast- forward 2 decades later: Dr. Paine is developing one of the most powerful ecological concepts (keystone species), one that continues to influence our science and conservation efforts to this very day. Using the rocky shoreline of the Pacific North West as his coastal backyard, he is showing how a few sea stars dramatically dictate what a rocky shoreline looks like.

By eating lots of mussels that outcompete wimpy algae and anemones for space, the sea star allows a lot of different species to stick around. In other words, the sea star maintains species diversity of this community by preventing the mussel bullies from taking over the schoolyard. That’s one simple, but powerful concept….one species can be the keystone for maintaining a system. Lose that species, and you lose the system.

Lightning Whelk

A large lightning whelk found on Bay Mouth Bar in December of 2010.

Ok, let’s grab our ecological concept and travel back in time to Dr. Paine’s earlier research at Bay Mouth Bar. Wow, the precursor to the keystone species concept may be slithering around our backyard of Bay Mouth Bar in the form of the majestic horse conch! In this earlier work, the arrival of this big boy at the bar was followed by the disappearance of all of the former big boys (like this lightning whelk). By eating lots of these potential bullies, the horse conch may be the key for keeping this system so diverse in terms of other wimpy snails.

But why should anyone other than an ecologist care about the keystone species concept and its ability to link Bay Mouth Bar with rocky shorelines of the Pacific NW? Well, what if the lightning whelks eat a lot more clams than do other snails, and less clams buried beneath sediments means less of the sediment modification that can really promote seagrass (Read more about the symbiotic relationship between bivalves and seagrasses here)?  Thanks to Randall’s previous seagrass post, we can envision that less horse conchs could lead to less clams, less seagrass, and then finally a lot less of things that are pleasing to the eye (e.g., birding), to the fishing rod (e.g., red drum), to the stomach (e.g., blue crabs), and ultimately to our economy.

For the past two years, I’ve really enjoyed retracing Dr. Paine’s footsteps at Bay Mouth Bar. But lately, I’m feeling a little more urgent about needing to better understand this system because it’s disappearing (aerial images provided by USGS’s online database at http://earthexplorer.usgs.gov/).

To figure this out, we repeat a lot of what Dr. Paine did five decades ago. At the same time, we are testing some new ideas about how this system operates. For example, if the horse conch is the keystone species, is it dictating what Bay Mouth Bar looks like by eating stuff or by scaring the bully snails? How exactly does or doesn’t the answer affect clams, seagrasses, birds and fishes?

Luckily, because this system is so close, with some persistence and some good help, we’ll soon have good answers to those questions.

Cheers,

David

Ps: Many thanks to Mary Balthrop for helping us access this awesome study system every month.

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

P1000139

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: