Tag Archives: marine biology

The making of an experiment

Dr. Randall Hughes FSU Coastal & Marine Lab

“Wow, quite the set-up! I am jealous of that space!

“…As a side question, how did you pump the cue water to all your tubs, a peristaltic pump? Was it just gravity? Seems like quite the complicated set-up.”

Excerpts from a comment on Randall’s September 28th post, Scared Hungry.  Read the whole comment here.

IGOR chip- employment 150This recent comment by John Carroll made me realize that there are a lot of unsung heroes at the lab that don’t typically get credit for the essential work that they do to facilitate our research. So here is a ‘behind-the-scenes’ look at setting up an experiment:

1. The idea. This is the main part that I can take credit for, though even then an idea usually stems not simply from my brain, but from a paper I’ve read, a conversation with a colleague or student, or an observation in the field.

2. The infrastructure. Each experiment has its own specifics, but in my research there are generally 3 main requirements:

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The "small" deck, used by David and me for mesocosm experiments with snails, crabs, plants, oysters - you name it!

a. Space. FSUCML has numerous tanks and related facilities for use in research (Visit the Lab site here.). Of course, I often have specific needs or desires, and thus my first step is usually to speak to Mary Balthrop, our Associate Director, and then to Dennis Tinsley, our Facilities Manager. Both Mary and Dennis show a great deal of good humor in receiving my seemingly hair-brained requests (e.g., a deck that can hold 16 plastic kiddie pools full of sand and water!), and they work with me to find (or devise) a suitable space to get the job done. Our incredible carpenter, Dan Overlin, then has the task of modifying or creating that space.

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The newer "large" deck, obscuring the view of the small deck closer to the water's edge

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Another view of the small deck, with the large seawater tanks in the background. (Photo credit: Nancy Smith)

b. Seawater. Since we work with marine critters, access to seawater is critical. FSUCML pumps seawater from the bay in front of the lab into large holding tanks that feed the entire facility.

Mark Daniels and Bobby Henderson then create the plumbing system that gets that water where it needs to go. They know everything there is to know about PVC pipes, water filters, pumps – you name it! As I mentioned in my response to John, it was Bobby who came up with the incredible pump apparatus (and several subsequent revisions) that has enabled us to conduct several experiments examining the effects of predator cues on prey behavior.

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Robyn and Emily working to set up a recent experiment on the large deck. Although the plants love all the light, we decided to erect a tent as a refuge from the sun/heat.

c. Light. When working with plants, light is key. I’m fortunate to have access to a greenhouse, as well as abundant outdoor space at the lab to set up experiments. Or perhaps I should say once-abundant outdoor space, since David and my decks now cover a good chunk of it! Dennis is a pro at thinking of suitable and available spaces to squeeze in a few tanks.

Robyn and Emily releasing grasshoppers into one of our cages. (Photo credit: Nancy Smith)

3. The supplies. Once the infrastructure is in place, it’s time to buy the supplies needed to make each experimental unit. The job then falls to Kathy Houck and Maranda Marxsen to explain to the accountants at FSU why I purchased several large bolts of tulle fabric (grasshopper cages), or 24 pair of knee-high panty hose (they make great filters when filled with gravel), or lots and lots of nail polish (for marking snails). For field experiments, Sharon Thoman is helpful in arranging vehicles and boat reservations, sometimes at the very last minute!

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Robyn and Liz cheerfully using nail polish to mark snails

 

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A thundercloud looms in the distance. Once this summer we were stranded in a storm and Dan came to retrieve us.

4. Set-up. Once things start to come together, there are inevitable surprises the crop up. In our recent predator-prey experiments, we had issues with flow from the pump being greater than that from the regular seawater lines, which required some brain-storming from Bobby, David, Kelly, Meagan, and myself. Or, a plumbing line will clog, and I’ll run to find Mark.  Or, we’ll get stranded in a thunderstorm while collecting mud crabs and Dan will come pick us up.   At least we often provide fodder for funny stories!

5. The experiment. And at last, the actual experiment can begin. When I come up with particularly high-maintenance experiments, it’s useful to utilize the lab dorms for the night. Linda Messer is always understanding of last minute housing requests and changes, making sure the lights (and, more importantly, the A/C) are on! Sometimes, the experiment itself is much shorter than the time required to set it up – duration never seems to equate with complexity. But one of the benefits of consulting with the staff is to ensure that the same space can be used for multiple purposes. And the second experiment is always easier to set up than the first!

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

Scared hungry?

Dr. Randall Hughes FSU Coastal & Marine Lab

A hardhead catfish, one of a mud crab's primary predators on North Florida oyster reefs.

IGOR chip_ predators_NCE 150As David has mentioned previously, predators can affect their prey by eating them (a very large effect to the prey individual concerned!) or by changing their behavior. And exactly how the prey change their behavior can have large consequences for the things that they eat. For instance, if you’re out camping and hear a bear lumbering around, do you quickly pack up all your food and put it out of reach of the bear and yourself? Or do you quickly eat as much as you can?

This summer we worked with Kelly, an undergraduate from Bridgewater College, to document how mud crabs deal with this dilemma of getting enough to eat but not getting eaten themselves.

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Kelly with the broken down truck on an ill-fated return trip from St. Augustine.

Specifically, we wanted to know how they respond to the presence or absence of catfish, and how this response affects the survival of juvenile oysters. Sounds straightforward, right? Well, yes, in concept, but as Kelly quickly discovered, putting that “on paper” concept into reality at the lab took a lot of time and effort!

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First, she had to get the “mesocosms” (aka large tubs) ready to serve as adequate habitat for the crabs, with plenty of sand and dead oyster shell for them to hide in.

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Next, Kelly took individual juvenile oysters, or “spat”, and used a marine adhesive to attach them to small tiles that we could distribute among all of the mesocosms.

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Juvenile oysters attached with Zspar (a marine adhesive) to a tile so we could assess mud crab predation.

 

You may have noticed that I mentioned catfish, and that these mesocosms are not particularly large relative to the size of a catfish. Never fear – because we wanted to separate the effects of catfish cues from the effects of catfish actually eating mudcrabs, the catfish were kept in a much larger tank, and then water from this tank was pumped into the mesocosms receiving catfish cues. (Setting up the pump and tubing to 60+ tanks was a several-day effort in itself!)

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The catfish tank, with tubing carrying catfish "cues" to individual mesocosms.

Once everything was in place, it was time to collect the mud crabs. We couldn’t collect the crabs gradually, because they like to eat each other when confined in small spaces in the lab, so we garnered as much help as we could and held our own little mud crab rodeo. (And got caught in quite a thunderstorm in Alligator Harbor, but that’s another story).

Finally, it was time to start the experiment! We measured the size of each of the mud crabs, added them to the mesocosms, and let them eat (or not). Each day, Kelly would count the number of live oysters remaining, and she would remove a few mud crabs from some of the mesocosms to simulate catfish predation. There were a lot of moving parts to this experiment, and Kelly did a great job managing it!

And what did we find? Turns out that individual mud crabs actually eat more juvenile oysters when they are exposed to catfish cues and the removal / disappearance of some of their neighboring mud crabs, compared to just the removal of neighboring mud crabs or the absence of catfish cues. But overall, the the removal of mud crabs have a positive effect on oyster survival. (Even though individual crabs may eat more, there are not as many crabs around, so it’s a net positive for oysters.)

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Mud crabs ate more oysters per individual in buckets with exposure to catfish cues and high rates of manual removal of mud crabs (to simulate predation).

Kelly has returned to classes, so we’ve now recruited a new assistant, Meagan, to help us with an experiment to address the additional questions that inevitably arise as you learn more about a system – for example, do mud crabs behave differently if catfish are around all the time versus only some of the time? We’ll keep you posted…

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

Switching gears: from kayak to office cubicle

Hanna Garland FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150As fast as summer approached, it is now over; and for myself, it marks the closing of an intense field season and the beginning of my first year as a graduate student. However, this does not mean that the experiments, laboratory work, and data collection is put on hold. There is still plenty of work to check off the “to do” list that seems to never get any shorter.

My last post introduced the scientific question I was hoping to answer and the reason for studying the relationship between crown conchs and oysters in the Matanzas River as opposed to a different location. While I did not answer the question entirely (that would be far too difficult to accomplish in one summer), I was able to establish a strong, preliminary data set that I can now analyze and re-configure in order to improve upon this research next season.

Similar to methods described in David and Tanya’s posts, the construction of my experiment consisted of (much smaller) trenches dug for cage installation, Z-spar for attaching oyster spat to tiles, bumblebee bee tagging kits for marking appropriately weighed and measured oyster clusters, and various amounts of PVC for expensive data logger equipment housing. The fun meter never stopped ticking this summer in St. Augustine!

As I sit in my cubicle in my new office on campus, my mind cannot help but wander back to my life this summer driven by the time of low tide and whether I would have enough sunlight or energy to kayak out to one more site. To my surprise, the running of my experiment was manageable and actually became a relaxing routine. Data collection was divided into three categories: conch surveys, oyster health, and data logger maintenance. The number of conchs found on the experimental reefs was recorded in order to quantify the varying densities of these predators at each site. The health of the small oysters attached to tiles as well as the tagged larger clusters were assessed based on the number of live and dead. The data logging instruments record the water temperature, salinity and amount of tidal inundation occurring at each of my six experimental oyster reefs every five minutes (so there are a lot of data points to be analyzed here!) and require periodic scrubbing to remove algal and barnacle growth.

While the daily workload may seem light as far as stress levels; the fine print of every step of an experiment can be a tremendous mix of emotions. The hope for not just data but “good” data is something that all scientists share; however, this does not mean that conducting research needs to be filled with anxiety. The outlook that I aimed to have this summer was more based on the feelings of excitement and opportunity rather than high expectations that may or may not be met. To be able to conduct this study in such an ecologically rich environment surrounded by intelligent, supportive, and proactive people and institutions is an accomplishment in itself.

While my data set still requires endless hours of manipulation and analysis, the general outcome of my experiment this summer revealed that there is in fact an oyster health gradient occurring along the Matanzas River, with a change in health occurring around the Matanzas Inlet. In tandem with this increasing oyster mortality moving from my sites north of the inlet to the sites south; are high densities of crown conch populations on the southern reefs, with a decrease in these populations moving towards reefs north of the inlet. Furthermore, environmental factors (water temperature, salinity and tidal inundation data collected by my instruments) will be considered when looking at these patterns.

As a way to better quantify the health and size of the oyster community as well as the density of the resident species (such as crabs, worms, and other amphipods) that inhabit oyster reefs; I surveyed and sampled background reefs at each of my six experimental sites. Long story short, this meant that I randomly selected four new oyster reefs at each site in which I collected environmental data and basic reef characteristics (type of reef, location, dimensions), conducted conch surveys, and collected every living oyster cluster, dead shell, crab, piece of biota, etc. inside of a 0.25 x 0.25 meter quadrat. After washing away the mud, extracting the living organisms and preserving them in ethanol, and weighing, measuring, and recording each live and dead oyster, I have developed a solid database of the oyster reef communities at each of my sites. This will help to better describe the type and abundance of species present at each site.

Oyster reef communities impact us in more ways than providing a tasty appetizer at a restaurant. Not only do they provide a habitat for commercially and ecologically important species, but they also serve to locally improve water quality and prevent erosion. Oyster reefs are complex communities that are in a state of decline along the Florida coast. Unfortunately, unhealthy oysters cause unhealthy or collapsed resident species communities because these organisms depend on oyster reef habitats for food, shelter, and other important aspects of their life cycle. This experiment and preliminary data set provides insight to changing food web dynamics occurring not only along the Matanzas River but in all oyster reef communities.

Apalachicola oysters

Tasty as they are, oysters have a far greater ecological- and economical- value when they're alive in their oyster reefs.

Whether you are enjoying seafood for dinner or driving on a bridge over estuarine environments, keep in mind the important role each individual species plays in a larger community structure. Our actions upstream of these fragile habitats impact everything from microscopic worms to the maturing oyster spat and larger fish populations. As my project evolves, I hope to not only strengthen the scientific community but also raise awareness among people who unknowingly influence an aspect of oyster reef habitats.

 

Summer Chaos and The Tower of Cards

Throughout this week, Dr. David Kimbro has been updating us about the premature dismantling of his lab’s summer experiment in preparation for Hurricane Irene.   Before this turn of events, David’s lab tech, Tanya Rogers, had written this account detailing how much work went into assembling the experiment and all of its (literally) moving parts.

Tanya Rogers FSU Coastal & Marine Lab

Beautiful, isn't it? But working on oyster reefs in Jacksonville hasn't been as nice as its sunrises.

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For many labs, the summer field season is a period of intensity and madness: a time for tackling far too many projects and cramming as much research as possible into a preciously short window. It’s a demanding flurry of activity occasionally bordering on chaos. The greatest challenge for technicians like myself is to maintain order in this pandemonium of science, and to carry out as much field work as efficiently as possible without going crazy.

Continue reading

Are two friends better than one?

Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip- biodiversity 150

Sand fiddler crab.

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

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

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

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

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

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

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

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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.
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