Category Archives: Wildlife in North Florida- Critters Big and Small

Crown Conchs, Parenting, and Walks Along the Gulf Coast

We’re pleased to introduce our newest blogger, Jessie Mutz. A graduate student in the Florida State University Department of Biological Science, Jessie will be taking a closer look at some of the many fascinating plants and animals in our area. In the process, she’ll introduce us to FSU students and faculty conducting research across various ecosystems.  She starts in a place familiar to this blog when it comes to FSU research- our very own Forgotten Coast.
Jessie Mutz Graduate Student, FSU Department of Biological Science

With summertime officially and emphatically here in North Florida, many of us are coastward bound. Like long walks on the beach?  As it turns out, you’re not the only one.

Low tide on the Gulf Coast. Photo by Scott Burgess.

Low tide at the FSU Coastal & Marine Lab, St. Teresa, FL. Photo by Scott Burgess.

Meet Dr. Scott Burgess, a marine evolutionary ecologist and one of the newest faculty in FSU’s Department of Biological Science. Although it’s only the start of his first full summer in Tallahassee, Scott has already been hitting the beach – a prime location for researching the reproductive strategies of intertidal invertebrates like the crown conch, Melongena corona. “This area has a lot of species with an unusual life history type, one that is typically less common in other areas,” he says. “So that’s a big interesting thing: Why are there lots of these weird ones here? Why have all of the species chosen this particular life history in this area of the world?” Continue reading

Bird Watching & Nature Writing: Susan Cerulean at Bald Point

Video: bird watching, nature writing, and possibly the best sunrise spot on the Forgotten Coast. Author Susan Cerulean joins us at Bald Point State Park.

Rob Diaz de Villegas WFSU-TV

Susan Cerulean and I are watching a bufflehead duck dive for food by an oyster reef.  We’re at Bald Point State Park, and Susan is putting me in tune with nature’s cycles.  “You can’t know when that last one’s left,” she says of the duck, which should soon be departing for the north.  This is the seasonal cycle, warming and cooling that spurs many of the birds we’re seeing to start continental and intercontinental flights. Continue reading

Interning at the Gulf Specimen Marine Lab: Hands On

Video: Interns at the Gulf Specimen Marine Lab in Panacea, FL, get hands on experience working with marine life and equipment.

Rob Diaz de Villegas WFSU-TV

We’re on a boat, speeding through Apalachee Bay on our way back to land.  We’ve accompanied Cypress Rudloe and two Gulf Specimen Marine Lab interns on a trip to collect samples.  Buckets full of octopus and sea urchins slosh as I take a good look to my left and right and get a firm perspective of where I am.  We’re several miles from the St. Marks Lighthouse; it stands out unmistakably as it was designed to do.  Smoke unfurls over it and into the Gulf, from a controlled burn on the St. Marks National Wildlife Refuge.  I look left and see the mouth of the Ochlockonee River, and follow the contour of the land as it curls out of sight to Alligator Point.  These interns are preparing for a life that keeps them in places like this.  Bravo.

P1080062-smallerOf course, it’s more than merely being outdoors that they’re getting out of the deal.  They’re learning about sea turtle rescue, collecting specimens in the wild, and outreach activities.  This includes leading tours and taking the Seamobile out to where kids who don’t always make it to the coast can touch a horseshoe crab.  The day after our trip, the Seamobile is going to Thomasville, GA for a festival.  The stingray and horse conch that inhabit the tank at the rear of the mobile aquarium will be traveling dozens of miles from their home, but to a place bound to their home nonetheless.  Making that connection is part of the educational outreach that interns perform.

“We take the Seamobile around and do programs on sea turtles, coastal watersheds, marine invertebrates,” Tom Harrah told me as he loaded some critters into one of its tanks.  Tom manages the Seamobile and the intern program at Gulf Specimen.

Just a few miles west of Thomasville is the upper Ochlockonee River.  This makes it a part of Apalachee Bay’s coastal watershed.    If rivers are the strings that connect places like Thomasville to the bay, then standing on this boat I am over a knot.  Two watersheds meet here, the Ochlockonee and St. Marks, rivers whose mouths I can alternately see by turning my head one way or the other.  Somewhat by design, every video I’ve produced over the last few months tugs at this knot, and standing here I trace my way backwards to farms and through underwater caves.

Both Full Earth and Turkey Hill Farms compost using fish waste. The compost should release less nitrogen into waterways. Both farms are near rivers that drain into Apalachee Bay, so a more efficient means of fertilizing their crops helps keep the watershed cleaner, ultimately benefiting the species that provide fuel to their plants.

Both Full Earth and Turkey Hill Farms compost using fish waste. The compost should release less nitrogen into waterways than synthetic fertilizers. Both farms are near rivers that drain into Apalachee Bay, so a more efficient means of fertilizing their crops helps keep the watershed cleaner, ultimately benefiting the species that provide fuel to their plants.

In our last segment we covered two farms in the Ochlockonee watershed.  Full Earth Farm co-managers Katie Harris and Aaron Suko are cognizant of where their farm is in relation to the river, and it influences the way they work their land.  “We don’t want to negatively impact the local waterways and the groundwater.” Aaron told me. “That’s, I’d say, one of the primary reasons we don’t use synthetic fertilizers.”  In our first segment on the Red Hills Small Farm Alliance, I talked to Louise Divine.  She and her husband, Herman Holley, run Turkey Hill Farm just east of Tallahassee, and near to a small waterway named Black Creek.  Like Full Earth, Turkey Hill is an organic food grower.  And like Aaron and Katie, Louise and Herman are well aware of their place in the watershed.  “I think about it every day.” Louise said.  “I think about it when I drive down the highway and I see Roundup sprayed everywhere.  And I know that that Roundup ends up in Black Creek and I know that Black Creek goes into the St. Marks and I- it makes me insane.”

Excess nitrates from fertilizers figure prominently in stories we’ve done on Wakulla Springs.  It runs off of lawns in Tallahassee and down streets, into sinkhole lakes like Upper Lake Lafayette or into Lake Munson, a heavily polluted waterway that drains into Ames Sink.  Dye trace tests have linked Ames Sink to the springs, its water running through one of the largest underground cave systems in the country.  Nine miles or so after its water emerges from Wakulla Spring, the Wakulla River meets up with the St. Marks.  Wakulla Spring has suffered from an increase an algae due to excess nitrates.  Perhaps due to tidal influence, the lower river’s water appears to be cleaner.

Chloe Jackson is an honors biology student at Florida State University. She interned at the Gulf Specimen Lab over the summer, and is currently using their dock for an experiment using recruitment tiles (which should look somewhat familiar for those of you who've been following In the Grass, On the Reef over the last few years).

Chloe Jackson is an honors biology student at Florida State University. She interned at the Gulf Specimen Lab over the summer, and is currently using their dock for an experiment using recruitment tiles (which should look somewhat familiar for those of you who followed In the Grass, On the Reef over the last few years).

Both the St. Marks and the Ochlockonee provide an important influx of freshwater to coastal ecosystems.  “There’s a high level of biodiversity in this area” Tom Harrah said.  “There are a lot of rivers coming into the ocean, dumping nutrients.  And there’s just animals everywhere.”*

Tom was new to the area when he volunteered at Gulf Specimen as an FSU biology major.  Eight years later, he’s still here working and enjoying these natural resources.  Intern Cara Borowski’s love of these natural resources manifested itself in a different way, as we cover in the video above.  For her, the thrill is getting kids interested in ecology and fostering a spirit of stewardship.  When she entered the program, she was aiming to be a research biologist.  Now, she’s thinking more about education.  Without an opportunity to host field trips and take the Seamobile to schools, she might never have considered this career path.

 *If you’re confused about the roles of nutrients, which can cause lethal algal blooms but also provide a foundation for all life on earth, I’ll direct you to this blog post written by Dr. David Kimbro about the nitrogen cycle.

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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Snakes, Eagles, & Gopher Tortoises at the E.O. Wilson Biophilia Center

Rebecca Wilkerson WFSU-TV

In the coming days, we refocus our attention to the coasts as we gear up for the world premiere of In the Grass, On the Reef: Oyster Doctors. This is the culmination of almost four years of collaboration with Dr. Randall Hughes and Dr. David Kimbro. Together, we have explored the salt marshes, oyster reefs, and seagrass beds that fuel Florida’s Forgotten Coast. Stay tuned for more information on the premiere event and opportunities to join us on coastal EcoAdventures.
Regena, one of the two American Bald Eagles housed at the E.O. Wilson Biophilia Center.

Regena, one of the two American Bald Eagles housed at the E.O. Wilson Biophilia Center.

For this video we take a step back from the coast and travel inland to visit one of Florida’s environmental education centers. The E.O. Wilson Biophilia Center is named after Dr. E.O. Wilson for his work in conservation, preservation and restoration. Dr. Wilson contributed to the development of several new academic specialties in biology and paved the way for many global conservation efforts. He also coined the term “biophilia”, meaning  “love of all living things.”  His life’s work and achievements set the standard for the development of the center and its various education programs.

The Biophilia Center is surrounded by Longleaf Pine ecosystem and is ideal for educating students on the importance of biodiversity. The programs offered through the center are available to fourth and seventh grade classes. While the center focuses on serving students, teachers and professional audiences, it is not your average field trip:

  • Students visit the center for either a 2 or 4-day program. Educators from the Biophilia Center have written hundreds of pages of curriculum that meet state standards. The curriculum can be incorporated into their classroom activities before and after their visits.
  • Currently transitioning from a private foundation to a public foundation, the center relies heavily on donations, grants, and volunteers. This allows the center to host schools free of charge. Schools only pay for transportation and substitute instructors for their classrooms.
  • The Biophilia Center is now open to the public on the first Saturday of every month. Each public day includes a focused educational program and activities based around that theme.
  • Twice a year, the center hosts a Special Needs in Nature in nature event, and they accommodate the special needs of visitors during regular programs as well. With the center also being accessible for visitors in wheelchairs, the educators hope to give everyone an opportunity to enjoy the facility and learn more about the world around them.

The E.O. Wilson Biophilia Center provides an opportunity for fun, hands-on learning about the natural world and the animals within. The educators also teach visitors how to interact with the natural world and appreciate all ecosystems, shaping visitors into budding naturalists.

Visiting schoolchildren handle an eastern indigo snake with "Turtle" Bob Walker.

Visiting schoolchildren handle an eastern indigo snake with “Turtle” Bob Walker.

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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?

Diversity- Getting by With a Little Help From (Salt) Marsh Friends

2-Minute Video: Marsh cordgrass, needlerush, sea lavender, mussels, periwinkle snails, and fiddler crabs: diversity in the salt marsh.

In Randall’s last post, she looked at whether genetic diversity within the salt marsh foundation species– smooth cordgrass- made for a stronger marsh (and by stronger, of course, we mean better able to shelter yummy blue crabs for people and sea turtles). In today’s post and video, Randall examines how the combination of plants and animals around cordgrass- the species diversity of a marsh- might play a role as well.
Dr. Randall Hughes FSU Coastal & Marine Lab/ Northeastern University

IGOR chip- biodiversity 150Even though salt marshes often look like one big sea of green in the intertidal, there are plants and animals other than marsh cordgrass around. And even though I devote a lot of effort to understanding the effects of diversity just within cordgrass, these other species are also important – no marsh is an island. (Well, actually they are, but you get the analogy.)

Fiddler crab found in a St. Joseph Bay salt marsh.So who is important, and why? There are at least two animals that can be classified as “friends” of cordgrass – fiddler crabs and mussels. Fiddler crabs create burrows that allow oxygen to get down in the sediment, and cordgrass roots appreciate that oxygen. The fiddler crabs also aerate the sediment during their feeding, and they can excrete nutrients that the plants use to grow.

As an aside, fiddler crabs are also irresistible for kids (and maybe adults too!).

Mussels aren’t quite as charismatic as fiddler crabs, but they like to nestle around stems of cordgrass, and the byssal threads that they use to attach to one another and to the sediment can help prevent erosion. In addition, they excrete nutrients and other organic material as a byproduct of their filter-feeding, and the plants take advantage of these nutrients.

While investigating the relationship between mussels and marsh cordgrass, Randall’s graduate student, Althea Moore, noticed that mussels also seemed to often accompany sea lavender in the marsh. This led to a separate study for Althea.

So who is MORE important, mussels or fiddler crabs? We did an experiment to test that question, or really, to test whether having mussels and fiddler crabs together is better than having just one or another. The answer? As with much in ecology – it depends. For one, it depends on what you measure. If you look at the number of cordgrass stems, then fiddler crabs are the better friend – cordgrass with fiddler crabs does better than cordgrass without fiddler crabs, regardless of whether you have mussels or not. But if you look at how tall the plants are (another important characteristic in the marsh), then mussels are the better friend, but only when fiddlers aren’t around. And if you look at the amount of organic content, mussels increase organic content at the sediment surface, whereas fiddlers increase it belowground. In the end, the take-home message is that the more things you measure about the marsh, the more important it becomes that you have both mussels and fiddler crabs in order to be the “best”.

In the process of doing the experiment I described above, Althea (my graduate student) noticed that when she was out in the marsh, she often found mussels in and around sea lavender (Limonium) plants more often than she found them around cordgrass. She became interested in finding out whether the mussels benefit the sea lavender, the sea lavender benefits the mussels, or a little bit of both. She’s still working on the answer, but it just goes to show that although we often tend to focus on who eats who (think Shark Week) or who can beat who (Octopus vs. Shark, anyone? Or, for kids, there’s always Shark vs. Train – a favorite at my house!), there are just as many instances of species helping one another (not that they always intend to).

Of course, it’s not just animals helping (aka, facilitating) plants – plants can help other plant species to. We’ve shown through a series of experiments that cordgrass benefits from having its tall neighbor needlerush (Juncus roemarianus) around, but only if the snails that like to graze on cordgrass are also present. Nothing is ever as simple as it looks in the marsh…

Music in the piece by Revolution Void.

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.

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.

 

A mud crab ready for his hearing test.

Can crabs hear? (A testament to the benefits of collaboration)

Over the last few weeks, we’ve explored the ecology of fear in oyster reefs. What makes oysters too scared to eat, potentially keeping them from reaching market size or filtering water? What makes mud crabs too scared to eat oysters, giving the oysters a better chance to succeed? New research by Dr. Randall Hughes and Dr. David Kimbro might change the way we understand fear in mud crabs.
Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150When we started the In the Grass, On the Reef project, Rob (WFSU-TV Producer Rob Diaz de Villegas) embarked on a crash course learning about oyster reefs and salt marshes, biodiversity, and non-consumptive predator effects.  While you’re most likely familiar with those first few terms, the last one – non-consumptive effects – is a bit of a mouthful and hasn’t exactly made the list of new slang words of 2013.  The term refers to the ability of predators to SCARE their prey even when they don’t EAT them, causing the prey to hide, or eat less, or change their size/shape to make it less likely that they will be eaten.  Of course, these changes are only possible if the prey realizes the predator is there before getting eaten!  There are several “cues” that prey can use: (1) they can see them (visual cues); (2) they can feel them (physical cues); or (3) they can “smell” them (chemical cues).  This last category is really common in the ocean, especially with slimy snail or fish predators that give off lots of chemicals into the water!

As Rob was learning more about the fish predators that we find on our oyster reefs, he discovered audio clips of the sounds that several of these fish make.  Putting 2 and 2 together, he posed a simple question to David and me: Can mud crabs use fish sounds as a cue that their predators are near?

Housam collecting juvenile clams attached to oyster shells for use in the experiment.

To be quite honest, David and I didn’t have an answer.  But, we knew how to find out – do the experiment(s)!  We enlisted Housam Tahboub, an undergraduate at the University of Michigan Flint, who wanted to do his summer Honors project in our labs.  (Little did he know what he was getting into.)  And then we set off on a crash course in bioacoustics, underwater speakers, and crab torture chambers (more on that in a minute).

Rob’s question really has 2 parts:
(1) Can crabs hear (anything)? (They don’t have ears.)
(2) Do crabs respond to the sounds of their fish predators?

A mud crab ready for his hearing test.

A mud crab ready for his hearing test.

To answer #1, we paired up with Dr. David Mann at the University of South Florida. 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 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 I know it looks like crab torture, all the crabs survived the experiment!

A mud crab submerged in the acoustic chamber

A crab submerged in the acoustic chamber.

Once the crab was immobilized and the electrodes were in place, we submerged the crab in a tank full of seawater that had an underwater speaker in it. We then played a series of acoustic stimuli of different volumes and frequencies and quantified the response recorded by the electrode. The really nice thing about this method is that we don’t have to train the crabs to tell us when they hear the noise like in the hearing tests that you and I take!

A marked oyster shell with juvenile clams glued on it as a crab buffet.

To tackle question #2, we set up a mesocosm experiment at FSUCML. Each mesocosm (aka, bucket) had sediment, a layer of loose oyster shell to serve as habitat for the crabs, and 5 mud crabs that we collected from nearby oyster reefs. We also added some juvenile clams glued to a few marked oyster shells in each mesocosm – this way, we could count the number of clams eaten over time and determine whether crabs were eating more or less in response to the predator sounds.

To run the experiment, we downloaded sound clips of several different crab predators – toadfish, black drum, and hardhead catfish – as well as 2 non-predators to serve as controls – snapping shrimp and a silent recording. Housam put these on his iPod, connected it to an amplifier and underwater speaker, and we were ready to begin.

(Well, let’s be honest, it wasn’t quite that simple. Housam read a lot of papers to figure out the best methods, spent lots of time collecting crabs, and logged lots of hours (both day and night, in the company of mosquitoes and biting flies) moving the speaker from tank to tank before we finally settled on a good protocol. He even tried all of this in the field! But when his summer ended, Tanya, Phil, and Ryan kindly stepped in to run the rest of the trials we needed.)

But we didn’t stop there. We know from our earlier experiments with Kelly Rooker (another undergraduate researcher) that the crabs don’t eat as much when exposed to water that hardhead catfish have been swimming in, most likely because they can detect chemicals in the water that the fish give off. So which cue generates a stronger response – chemical cues or sound cues? Time for another experiment!

Phil checks on the mesocosm experiment at FSUCML

In this version, the mesocosms were assigned to one of 4 combinations: (1) a silent recording, paired with water pumped from a tank holding 2 hardhead catfish into the mesocosm; (2) a recording of a hardhead catfish, paired with water that did not go through the catfish tank; (3) a recording of a hardhead catfish, paired with water from the catfish tank; (4) a silent recording, paired with water that did not go through the catfish tank. We again looked at the number of clams eaten over time to see how the crabs change their behavior.

This project has been a lot of fun, and it never would have happened were it not for Rob’s curiosity. We gave a preview of our results at the Benthic Ecology conference in Savannah, GA, last weekend. But we’ll have to wait until everything is reviewed by other scientists and published in a scientific journal before we can share all of the details here. So stay tuned!

Music in the piece by zikweb.

Black Drum recording used in the video courtesy of James Locascio and David Mann, University of South Florida College of Marine Science.

Catfish and toadfish recordings copyright University of Rhode Island.  They were obtained from dosits.org, under these terms:

Copyright 2002-2007, University of Rhode Island, Office of Marine Programs. All Rights Reserved. No material from this Web site may be copied, reproduced, re-published, uploaded, posted, transmitted, or distributed in any way except that you may download one copy of the materials on any single computer for non-commercial, personal, or educational purposes only, provided that you (1) do not modify such information and (2) include both this notice and any copyright notice originally included with such information. If material is used for other purposes, you must obtain permission from the University of Rhode Island. Office of Marine Programs to use the copyrighted material prior to its use.

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

Crown Conchs- Friend or Foe?

For today’s post, we shift our look at the ecology of fear from oyster reefs to the (often) neighboring salt marsh.  We know crown conchs are villains on oyster reefs, but might they redeem themselves “in the grass?”  If they live on the Forgotten Coast, it depends on what side of Apalachicola they live.
Dr. Randall Hughes FSU Coastal & Marine Lab
The Crown Conch (Melongena corona).

The Crown Conch (Melongena corona).

IGOR chip_ predators_NCE 150If you’re a fan of oysters and you read David’s previous post, then you probably don’t like crown conchs very much. Why? Because David and Hanna’s work shows that crown conchs may be responsible for eating lots of oysters, turning previously healthy reefs into barren outcrops of dead shell.  And we generally prefer that those oysters be left alive to filter water and make more oysters.  And, let’s be honest, we would rather eat them ourselves!

But, in something of a Dr. Jekyll and Mr. Hyde act, crown conchs can take on a different persona in the salt marsh. Here, the exact same species acts as the good guy, increasing the abundance of marsh cordgrass.  And more abundant marsh plants generally means more benefits for we humans in the form of erosion control, water filtration, and habitat for the fishes and crabs we like to eat.  How exactly does that work?

Periwinkle in Spartina predator experiment

The Marsh Periwinkle (Littoraria irrotata).

If you look out in a salt marsh in much of the Gulf and Southeast Atlantic, I can nearly guarantee that you’ll see a marsh periwinkle snail. Usually, you’ll see lots and lots of them. These marine snails actually don’t like to get wet – they climb up the stems of the marsh grass as the tide comes in. While they are up there, they sometimes decide to nibble on a little live cordgrass, creating a razor blade-like scar on the plant that is then colonized by fungus. The periwinkles really prefer to eat this fungus instead of the cordgrass, but the damage is done – the fungus can kill the entire cordgrass plant! So these seemingly benign and harmless periwinkles can sometimes wreak havoc on a marsh.

But wait a minute – if periwinkles cause all the cordgrass to die, then why do you still see so much cordgrass (and so many snails) in the marsh? That’s where the crown conch comes in.

Crown conch pursuing periwinkle snail

At the edge of a marsh at high tide, a crown conch approaches a periwinkle snail. As shown in the video above, the conch was soon to make contact with the smaller snail and send it racing (relative term- the video is of course sped up) up a Spartina shoot.

In marshes along the Gulf coast, there are also lots of crown conchs cruising around in the marsh (albeit slowly), and they like to eat periwinkles. Unlike other periwinkle predators such as blue crabs, the crown conchs stick around even at low tide. So when the periwinkles come down for a snack of benthic algae or dead plant material at low tide, the crown conchs are able to nab a few, reducing snail numbers. And fewer snails generally means more cordgrass.

Of course, the periwinkles aren’t dumb, and they often try to “race” away (again, these are snails!) when they realize a crown conch is in the neighborhood. One escape route is back up the cordgrass stems, or even better, up the stems of the taller needlerush that is often nearby. By causing periwinkles to spend time on the needlerush instead of grazing on cordgrass, or by making the periwinkles too scared to eat regardless of where they are sitting, the crown conch offers a second “non-consumptive” benefit for cordgrass. One of our recent experiments found that cordgrass biomass is much higher when crown conchs and periwinkles are present compared to when just periwinkles are present, even though not many periwinkles were actually eaten.

Periwinkle in Spartina predator experimentOn the other hand, if the periwinkles decide to climb up on the cordgrass when they sense a crown conch, and if they aren’t too scared to eat, then crown conchs can actually have a negative effect on the plants. This is exactly what David found in one of his experiments.  In this case, the tides play an important role – west of Apalachicola, where there is 1 high and 1 low tide per day, each tide naturally lasts longer than east of Apalachicola, where there are 2 high tides and 2 low tides per day.  The longer tides west of Apalach appear to encourage the snails not only to stay on the cordgrass, but also to eat like crazy, and the plants bear the brunt of this particular case of the munchies.

So even in the marsh, it turns out that crown conchs can be both a friend and a foe to marsh cordgrass, depending on how the periwinkles respond to them. And figuring out what makes periwinkles respond differently in different situations just gives us more work to do!

Music in the piece by Revolution Void.

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