Category Archives: On the Reef

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

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Can crabs hear? (Revisited, with answers!)

P1050260Four years ago, we traveled out into the oyster reefs of Alligator Harbor with Dr. David Kimbro.  It was both the start of an ambitious new study and of our In the Grass, On the Reef project.  Last June, we went back to those reefs with Dr. Randall Hughes as she, David, and their colleagues revisited study sites from North Carolina to the Florida Gulf.  In 2010, they sampled the reefs with nets and crab traps, and harvested small sections of reef.  This more recent sampling, which unfolds in the opening scenes of our recent documentary, Oyster Doctors, was conducted with underwater microphones.  Randall explains how sound became a tool in further understanding fear on oyster reefs.

The research in the following post was conducted while Randall and David worked at the FSU Coastal and Marine Laboratory.

Dr. Randall Hughes Northeastern University

A little over a year ago, I wrote about our research project, motivated by a question from WFSU producer Rob Diaz de Villegas, to test whether crabs can hear the “songs” made by their fish predators. At the time, the work had not been published, and so I was not able to share all of the juicy details. But now it has, in the Proceedings of the Royal Society B, so I can finally answer with a resounding YES!

To review a little bit, Rob’s question really had 2 parts:

  1. Can crabs hear (anything)? (They don’t have ears.)
  2. Do crabs respond to the sounds of their fish predators?

To answer #1, we paired up with Dr. David Mann. Dr. Mann is an expert in bioacoustics, and particularly in evaluating whether marine critters (primarily fish) can hear different sounds. We modified his methods slightly to accommodate our mud crabs – basically, we needed to immobilize the crabs on a ‘stretcher’ so that we could insert one electrode near the crab’s antennae, and another in the body cavity to pick up any background “noise” the crab may be produce that was not in response to the acoustic stimuli. Although it looks like mud crab torture, all the crabs survived the experiment!

Mud Crab Hearing TestWhat did we find? The crabs had a neurological response (i.e., they “heard”) a range of frequencies. They certainly wouldn’t ace any hearing tests, but if a sound is low- to mid- frequency and relatively close by, they can likely hear it. They do this using their statocyst, a structure containing sensory hairs that can detect changes in orientation and balance, and in this case, can detect changes in particle acceleration associated resulting from the acoustic stimuli.

Although cool to someone like me who is fascinated by marine biology, many of you are probably thinking “So what?”. And for that, we turn to the second part of our study, where we tested whether mud crabs change their eating habits in response to the songs made by their fish predators. We compared the number of juvenile clams that crabs ate when we played them either a silent recording or a recording of snapping shrimp (a common organism on oyster reefs that doesn’t eat crabs) to the number of clams that they ate when we played them recordings of songs from 3 fish that DO eat mud crabs – hardhead catfish, black drum, and toadfish. Apparently catfish and black drum songs are the same to a crab as the Jaws theme song is to me, because they hunkered down and did not eat nearly as many clams when they heard the calls of those two predators.

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Phil Langdon feeds a catfish in an iteration of a mud crab hearing experiment.  They had already noticed that mud crabs were eating less when they heard sounds made by catfish and other predatory fish.  Here, they sought to measure whether the response was more intense with chemical cues (pumped via those tubes into tubs), or predator sounds (played from underwater speakers).

So, now we know that mud crabs can hear, and that they don’t eat as much when they hear some of their predators. But we also know from our earlier experiments that these same crabs don’t eat as much when exposed to water that hardhead catfish have been swimming in, most likely because they can “smell” chemicals in the water that the fish give off. So which catfish cue generates a stronger response – sound or smell? Turns out that both cues reduce crab foraging and to about the same degree, although in our experiment the effects of catfish songs were slightly stronger than the effects of catfish smell.

So what’s the take-home message from this work? For one, it highlights that we still have a lot to learn about the ocean and the animals that live in it – we (and others) have been studying these mud crabs for years and never thought to consider their ability to use one of the 5 major senses! In addition, it’s a reminder that in studying the “ecology of fear”, or the effects that predators have on their prey even when they don’t eat them, we need to remember that few predators are silent, and the sounds that they make could be important cues that prey use to escape being eaten. And finally, it demonstrates that science can be really fun!

This material is based upon work supported by the National Science Foundation under Grant Number 1161194.  Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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Free Events Across Forgotten Coast Celebrate New WFSU Documentary

Update March 9, 2014 – We’d like to thank everyone who came out for one or more of our events on Saturday. It was a pleasure to meet all of you (photos will be posted soon).  If you missed the premiere, Oyster Doctors will air on WFSU-TV on Wednesday March 19, 8 pm/ 7 ct.  Look for it online shortly after.

(L to R) Graduate student Hanna Garland, WFSU videographer Dan Peeri, oysterman Shawn Hartsfield, and WFSU producer Rob Diaz de Villegas look on as Stephanie Buehler dives in to survey oysters in Apalachicola Bay.

Rob Diaz de Villegas WFSU-TV

Almost four years ago, WFSU began the coastal adventure that is In the Grass, On the Reef.  Now, we want you to join the adventure.  And not through the magic of video- we want you physically there with us (but yeah, we’ll still make a video).

On Saturday, March 8, at the Ft. Coombs Armory in Apalachicola, Florida, we’ll be premiering In the Grass, On the Reef: Oyster Doctors.  It’s the culmination of these almost four years of losing my shoes in oyster reef and salt marsh mud, of kayaking to field sites in rain, waves, wind, and in those winter tides where the water all but disappears.  It’s that visceral experience, as much as the research and ecology, that we’ve tried to make a part of our videos and blog posts.  Seeing and feeling that magical place where the land meets the sea underlines the need to better understand it.

Hanna kayaks towards oyster reef experiment sites in October of 2010.

Hanna kayaks towards oyster reef experiment sites in October of 2010.

In that spirit, we’ll be having a few EcoAdventures where you, our viewers and readers, can join in the fun and get up close and personal with the wild places of our coasts.  There are three opportunities, one in each county of Florida’s Forgotten Coast and in each of its major coastal features.  These are free events, but some have limited spots available.  So register early to be a part of a lottery for these trips (winners will be selected on February 28).

A kayak tour of the animal rich marshes and oyster reefs of the Wakulla Beach unit of the St. Marks National Wildlife Refuge.  A walk through the St. Joseph Bay State Buffer Preserve to see the south Florida plant that’s more frequently popping up in north Florida marshes.  And a boat ride connecting the Apalachicola River and its bay, and those troubled oysters that are iconic of the Forgotten Coast.

With these trips, we recreate the IGOR journey in miniature.  Dr. Randall Hughes, our collaborator and one of the “oyster doctors” of our new documentary, will lead us through these first two trips.  In Wakulla Beach, she’ll be joined by Dr. William “Doc” Herrnkind, a retired FSU Coastal & Marine Lab professor and a guru when it comes to the critters that we have followed in this project.  This will be my first time meeting him, though I have heard quite a lot about him over the years from our research collaborators and even members of the community.  When the BBC wanted horse conch footage in our area, this is who they called.

Media attention at Save the Bay Day in Apalachicola

Media and community members gather in front of the Franklin County Courthouse in Apalachicola. With Florida’s U.S. Senate delegation in town, residents sent a clear message: Apalachicola oysters deserve their fair share of water from the Apalachicola/ Chattahoochee/ Flint basin.

For our Apalachicola boat trip, we’ll be led by Apalachicola Riverkeeper‘s Dan Tonsmeire.  I could not be more pleased to have Riverkeeper involved in this event.  Participating in their RiverTrek adventures over the last two years, in addition to being a life changing experience, has added immeasurably to our coverage of the Apalachicola oyster fishery crash.  Of course, when I signed on to paddle in early 2012, I had no idea that Florida’s largest oyster fishery was so close to disaster.  Likewise, when we first applied for the National Science Foundation grant that funds this project, we wrote in a possible Apalachicola premiere not knowing that its oysters would become a large part of our story.

Since we embarked on this journey, Dr. Randall Hughes, Dr. David Kimbro and their crews have let us be there for the twists and turns, failures and successes, and ultimately the discovery that has taken their research in a fascinating new direction.  While pursuing this new direction into animal behavior and it effects on these productive ecosystems, they were also investigating oyster reef failures in drought stricken areas.  On the one hand, they have relentlessly pursued this idea that animal behavior, the menace of a predator, can influence the health of marshes, oyster reefs, and seagrass beds.  On the other hand, does any of that matter if nature one day turns its back on these coastal habitats and cuts off the water?  It’s a question we ask as we delve into this spectacular world.  We’d love for you to join us in Apalachicola for the premiere, and join us on the water (and, I won’t lie, in the muck) as we go In the Grass, and On the Reef, one more time.

Register to attend the premiere of In the Grass, On the Reef: Oyster Doctors and to participate in pre-screening EcoAdventures!

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Blue crabs are a commercially important species that rely on both salt marsh and oyster reef ecosystems. They are also important predators in these habitats, preying on marsh grass grazing periwinkle snails and oyster eating mud crabs.

This material is based upon work supported by the National Science Foundation under Grant Number 1161194.  Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
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Video: Turtles, Octopus, & Crabs at the Gulf Specimen Lab

Video: Critters galore at the Gulf Specimen Marine Lab in Panacea

Rob Diaz de Villegas WFSU-TV
Jack Rudloe feeding Nurse Sharks at Gulf Specimen Marine Lab

Gulf Specimen Marine Lab founder Jack Rudloe feeding nurse sharks.

If there’s one thing we have learned in 3-plus years of doing this project, it’s that everything eats blue crabs.  If you’ve watched our videos over the years, you’ve seen a gull eating one on Saint George Island.  You’ve seen (and heard) a loggerhead turtle crunch into one.  And in the video above, two octopi wrestle for the tasty treat at the Gulf Specimen Marine Lab in Panacea, Florida (That turtle shot was taken there as well, a few months back).  Lab founder Jack Rudloe spent some time with us, feeding sharks, hermit crabs, and various fish species.  It gave us a great chance to see many of the species that we cover in this blog, and many that we don’t, in action.

In the 50 years since Rudloe founded Gulf Specimen, the facility has served an eclectic range of services.

Its aquarium features many of the small critters that we’ve chronicled Randall and David studying in Alligator Harbor, Saint Joseph Bay, or Wakulla Beach.  You won’t see any orcas doing backflips for a fish treat.  These are the creatures of our coasts, many of them common (like fiddler crabs), some of them rare (like a white blue crab).  If it’s safe to touch the animals, you can (consult the signs on the tanks).

Loggerhead at Gulf Specimen Marine LabFor almost as long as its been open, Gulf Specimen has run a Sea Turtle Program to rehabilitate injured loggerhead and Kemp’s Ridley turtles.  They release 15-20 a year, many of which have swallowed fishing hooks.  The turtle in the aforementioned video is Allie the Loggerhead, released after a year in their care (full story here).  The loggerhead that tries to eat our GoPro camera in the video above is Little Girl, who is on display right now.

And then there’s the reason the lab was originally created, to provide specimens of animals to researchers, both medical and academic.  This keeps animals coming in and going out, so that the critter lineup remains somewhat fluid.

In their outreach in education initiatives, their goals mirror our own on the In the Grass, On the Reef project, only in a more up close and tactile manner.  They want you to know about the critters and their habitats, the threats facing them, and the benefits they provide us.  With their Seamobile, they can take that mission (and the critters) on the road to events like the St. Marks Stone Crab Festival.  After people crack open their claws, they could go and learn about the world their food had inhabited.  After the last year we have learned that this food only gets on your plate when there is a balance between these animals and their environmental conditions.  Sometimes, that balance is off, whether it is an overabundance of oyster drills in Apalachicola or, as we see in the video, octopus in crab traps.  It’s one thing to hear that crabs are being eaten.  It really comes alive, though, when you see it happening.  That’s mission we share with the Gulf Specimen Lab.

Over the next few months, we’ll be seeking out others who work to bring the big, wild, messy outdoors to you.  Is there anyone that you think we should be talking to? Let us know!

What is that octopus hiding under its tentacles?

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RiverTrek 2013 Preview: A Year in the Apalachicola River and Bay

Rob Diaz de Villegas WFSU-TV

RiverTrek paddlers are raising funds for the Apalachicola Riverkeeper, an organization whose mission is to “provide stewardship and advocacy for the protection of the Apalachicola River and Bay, its tributaries and watersheds…” (participating media members do not raise funds).  At the end of the paddle, on October 12, there will be a reception in Battery Park in Apalachicola.  There, people can greet the paddlers and bring non-perishable food items in benefit of Franklin’s Promise.  Franklin’s Promise aids the families affected by the failure of the Apalachicola Bay oyster reefs.

IGOR chip- gastronomy 150“The Good Lord giveth, and Georgia and the Corps taketh away.” Those words were spoken by Jon Steverson, Executive Director of the Northwest Florida Water Management District.  He was testifying before Florida senators Bill Nelson (D) and Marco Rubio (R) during a special field hearing to address the collapse of the Apalachicola Bay oyster fishery.  The high-profile event, held two weeks ago in Apalachicola, marked almost one year into a particularly turbulent era for this region.  Just one year ago, I was preparing to kayak the Apalachicola River for RiverTrek 2012.  The winter bars in the bay were just days away from opening.  When they did, a lot changed, including the nature of the RiverTrek videos we were to make, and the In the Grass, On the Reef project as a whole.

U.S. Senators Bill Nelson (D) and Marco Rubio (R) at the Senate Committee on Commerce, Science, and Transportation field hearing Apalachicola on August 13.

As I prepare to cover RiverTrek 2013 (October 8-12), the answers to the Apalachicola’s water flow problems remain elusive, and frustration remains high.  Much of that frustration is aimed, as one might gather from the first sentence of this piece, at the state of Georgia and the Army Corps of Engineers.  Thirteen days into the job as Mobile District Commander, Colonel Jon Chytka absorbed decades of displeasure at the Corps’ management of the ACF basin.  “I’m going to try to find out why they sent you,” said Senator Nelson, “Why didn’t they send the generals that I’ve been talking to?”  Part of the frustration stems from the rigidity with which the Corps follows the ACF Water Control Manual, and their interpretation of the authority granted them by congress.  The economic impact of fresh water on Florida’s seafood industry is not given as much weight as its economic impact on Georgia agriculture.   The Endangered Species Act of 1973 is the only guarantor that the river flow is not set below 5,000 cubic feet per second (cfs), which is how low it stayed for 10 months starting May 1, 2012.  That qualifies as the lowest river flow in recorded history, and only endangered mussels and gulf sturgeon kept it from being lower.  Senator Rubio asked whether the Apalachicola oyster would qualify for such protection.  Crassostrea virginica, the common oyster, is the main oyster species found on the east coast of this country and in the Gulf of Mexico.  The oysters you see on the fringe of the coast are the same species as the larger ones harvested from the floor of the bay.  Apalachicola oysters are the same species as Chesapeake oysters.  To the letter of the law, and despite massive decline in oyster reefs worldwide, it is not an endangered species.

This oyster was retrieved from Dr. David Kimbro’s oyster experiment in Apalachicola Bay. They found it dead, with its meat having been eaten. Like many of the dead oysters they’ve found, it has oyster drill egg sacs growing on it. Each of the sacs (here growing on the “chin” of the oyster) contains 10-20 drills.  Low freshwater input to the bay increases its salinity, making the bay hospitable to oyster predators such as drills, crown conchs, and stone crabs.

A further source of frustration with the Corps is the speed with which the Manual is being updated.  As Col. Chytka pointed out, the process began in 2008 and was complicated by lawsuits, the amount of input from stakeholders in the affected states (over 3,000 comments), and the “technical complexities” of the system.  He projected that a draft of an Environmental Impact Statement would be ready in the Summer of 2015, after which they’d reopen it to comments and then finalize by 2016.  The oyster industry may not have that kind of time.  “I don’t see any hope for the near future,” said Shannon Hartsfield, President of the Franklin County Seafood Workers Association. “We don’t have a near future.”

The best-case scenario for the bay, as determined by the University of Florida’s Oyster Recovery Team, is full recovery within a couple of years.  That’s dependent on being able to place a significant amount of oyster shell at the bottom of the bay.  So far, Hartsfield estimates that they’ve covered 35-40% of Cat Point, historically one of Apalachicola’s most productive bars.  By the end of the current shelling project, he believes that they’ll have covered 50% of another of the bay’s main bars, East Hole.  So, in addition to fresh water, oysters will still be lacking adequate substrate where spat could settle.  Additional funding will be needed to cover the bars fully.  There is, though, a glimmer of hope.

While frustration has remained high, so too has passion for the ecosystem and compassion for the people affected.  Says Hartsfield, “This is the first time, ever, out of all this disaster that Franklin County has experienced in the commercial (seafood) industry, that we’ve had any recognition.  And we appreciate it greatly.”  That recognition drew dozens to the steps of the Franklin County Courthouse that day to show support.  It has drawn researchers willing to work with oystermen to find solutions.  It has drawn a steady stream of regional and national media.  And it drew the United States Senate to a fishing town on Florida’s Forgotten Coast.  At the very least, lot of people are invested in finding a solution.

RiverTrek paddlers make their way to Sutton Lake, off of the Apalachicola River.  Last year, the water was too low to paddle to where the largest cypress trees in the Apalachicola watershed are found.  With a year of healthy rainfall, this year's paddlers will have better opportunities to explore the creeks and sloughs branching off of the river.

RiverTrek paddlers make their way to Sutton Lake, off of the Apalachicola River. Last year, the water was too low to paddle further into the lake, where the largest cypress trees in the Apalachicola watershed are found. With a year of healthy rainfall, this year’s paddlers will have better opportunities to explore the creeks and sloughs branching off of the river.

I’m one of the media members who have found themselves returning to cover the crisis, and it started with 105 miles of paddling.  Last year at this time, RiverTrek was to be a different perspective on our local ecology than our marsh, oyster reef, and seagrass videos.  A change of pace.  Instead, it kicked off a year of content that connected the river with the coast, and with the people who care for and rely on these resources.  I now find myself getting ready for this year’s journey with a better knowledge and feel for the story, but with much less certainty about the outcome.  RiverTrek will end after five days.  For this other, much larger Apalachicola adventure, we’ll all just have to keep on paddling.

For more information on RiverTrek 2013, visit the Apalachicola Riverkeeper web site.  To watch videos from last year’s Trek, click here.

Music in the video by airtone.  “Salt in the Blood” was written and performed by Brian Bowen.

This material is based upon work supported by the National Science Foundation under Grant Number 1161194.  Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.