I recently completed teaching a 2-week course in Field Marine Science at FSUCML. Nine undergraduate students and one graduate teaching assistant lived in housing at the lab for the duration of the course, and we were busy from virtually sun-up to sun-down each weekday with class activities. It was a lot of fun:
The students of Field Marine Science 2012 inspect what we caught trawling through a local seagrass bed.
A group of students works to complete our field survey before the sun sets.
Students hunting for mud crabs for a lab mesocosm experiment.
This year, we focused on oyster reef ecosystems, taking advantage of past and ongoing projects in the Hughes and Kimbro (aka, “Hug-bro”) labs. We conducted a field experiment, field survey, and mesocosm experiment examining sediment accumulation on oyster reefs – and all in just 2 weeks!
Students quantify sediment accumulation on oyster shells during our field experiment.
Students process the contents of cages from our field experiment, looking for crabs.
Well, the field experiment and survey were started ahead of time by Hugbro personnel, but the labor-intensive breakdown and sample processing tasks were handled by the class.
Surveying mud crab abundance on our experimental reefs.
After all that time spent learning about, walking around on, and handling oysters, everyone was ready to eat a few by the end of the second week!
An underwater camera gave us a great view of the seagrass!
In addition to gaining hands-on research experience, a goal of the class was to become familiar with common coastal habitats in northern FL. So we squeezed in a few trips to seagrass beds and salt marshes as well, enjoying the opportunity to ride on a boat that didn’t require paddles.
Happily preparing to snorkel in St. Joseph Bay State Park, FL.
We observed lots of sea hares as we snorkeled in St. Joe Bay.
And we were all happy to don snorkels and masks to explore the seagrass instead of gloves and boots for the oysters!
Results of a study by Feldon and colleagues demonstrating an increase in the quality of hypotheses included in graduate student research proposals when the students had teaching responsibilities.
As I catch up on the research projects that languished a bit while I was teaching, it is reassuring to think about the results of a recent study illustrating that teaching can increase the quality of research. Don’t get me wrong – I enjoy and value teaching for its own sake – but the tasks of teaching and research can often seem in competition with one another when time is limited (and when is time not limited?).
Additional results from the study by Feldon et al. showing better experimental design in research proposals written by graduate students that teach and do research.
Enter the study by Feldon and colleagues in the journal Science, showing that graduate students with teaching responsibilities formed better hypotheses and generated better experimental designs in their own research proposals than graduate students without teaching responsibilities. This benefit did not result from explicit instruction in hypothesis testing or experimental design geared towards the graduate students themselves – rather, the process of teaching scientific concepts to others made them better able to conduct research. So add to the inherent fun and satisfaction of teaching a boost to my research! Time to write a (better?) research proposal…
Serendipitous results are surely one of the most rewarding parts of experimental research. This past winter, I spent many weeks processing various frozen components of great cage experiment of last summer, including the several hundred spat tiles placed inside the different cages at all sites along the coast. It was while delicately measuring and shucking these little spat that I made one such unanticipated finding: Our oyster spat, unbeknownst to us, had become infested with pea crabs.
Pea crabs at various stages of development. The ones in the center are young crabs, as they appear in the stages immediately following infection of an oyster. The ones on the right are older, harder-carapaced crabs (most likely males, which may leave their hosts in search of oysters harboring females). The crab on the left is a mature female. The developing, orange-colored gonads are visible through the female’s thin carapace. Since mature females never leave the their host oyster, their carapaces (shells) are very soft and thin. This makes them very… squishy and pea-like.
You might have had the surprise of finding an oyster pea crab (Zaops ostreus) while shucking an oyster yourself. These small crabs live inside oysters and are a type of kleptoparasite, meaning they steal food from their hosts. An oyster gathers food by filtering water over its gills, trapping edible particles on its gills, and carrying those particles to its mouth using cilia (tiny hairs). Pea crabs sit on the gills and pick out some of the food the oyster traps before the oyster can consume it. By scurrying around inside oysters, pea crabs can also damage the gills mechanically. The pea crabs, like most parasites, don’t kill their hosts, but they can certainly affect the oysters’ overall health.
A gravid (egg-bearing) female pea crab next to the oyster spat in which she was living. The female, like most crabs, carries her eggs until they hatch, and then releases her larvae into the water. The baby crabs, when ready, will locate a new oyster host by smell.
As I was processing the oyster spat from all of our experimental sites (Florida to North Carolina) for survivorship, growth, and condition, I began to notice a surprising number of pea crabs living inside them and started to keep track. What’s interesting was not so much that the oysters had pea crabs, but that the percentage of oysters infected with pea crabs varied geographically. For instance, only about 25% had pea crabs in St. Augustine, Florida, whereas over 70% were infected at Skidaway Island, Georgia. Keep in mind that these spat all came from the same source and the same hatchery, so they all had the same starting condition. What’s more, I found that spat in Georgia which had naturally recruited to the tiles from the surrounding waters (of which there were quite a lot, and for which I also processed condition) rarely had pea crabs. Only about 5% of the recruits had pea crabs at Skidaway Island, Georgia. Why is there this huge difference in infection rate? Do the local oysters know something that the transplants don’t? How do these patterns in pea crab infection relate to other geographic patterns we’re finding? How does pea crab infection affect oyster condition? These and many more questions await to be addressed in further analyses and future experiments.
Imagine you’re watching a slasher movie starring mud crabs as the protagonists. A mud crab leaves the party in the muck under the oyster reef, where the other crabs are chomping down juvenile oysters. As he pokes his head out from between a couple of shells, you hear a drumming sound and you shout at the screen “Don’t go out there!”
It’s fun to anthropomorphize some of the freaky looking residents of an oyster reef. But these are the realities of living within the ecology of fear. Predator cues have a definitive impact on how the smaller, intermediate consumers such as mud crabs behave. That’s what David Kimbro, Randall Hughes & co. are studying in Alligator Harbor and at their sites across the southeast. Large predators send certain cues to their prey- perhaps a certain way they move in the water, perhaps. When the prey species sense that the predators are near, they cease activity- including the eating of juvenile oysters. That is how large predators help maintain a healthy oyster reef- they make intermediate consumers (mud crabs) eat less of the basal species (oysters, the foundation of the oyster reef habitat). Continue reading →
David and I are in Sydney, Australia, on visiting research appointments with the University of Technology Sydney. We arrived the first of the year, and after recovering from jet lag and getting our bearings, we embarked this week on setting up a couple of new experiments. We have great local “guides” – Dr. Peter Macreadie (UTS), Dr. Paul York (UTS), Dr. Paul Gribben (UTS), and Dr. Melanie Bishop (Macquarie University) – to introduce us to the field systems and collaborate with us on these projects.
Our seagrass and razor clam experiment is set up at Point Wolstoncroft in Lake Macquarie (north of Sydney).
What’s not to love about oysters? They clean the water, they’re delicious, and they have surprising economic value. Members of the Kimbro Lab found this unique oyster, which itself seems very loving, on one of their study sites. “Now I’ve seen a lot of weird-shaped oysters,” says lab tech Tanya Rogers,” but never one quite this perfect. I took it on a photoshoot this evening for some nice background and lighting.”
“Spat tiles” are a tool our lab commonly uses to measure the growth and survivorship of juvenile oysters under different conditions, and we’ve used them with varying degrees of success in many of the experiments chronicled in this blog. What these are essentially (in their final form, after a good degree of troubleshooting), are little oysters glued to a tile, which is glued to a brick, which is glued to a mesh backing, which is zip tied vertically to a post. Rob and I have put together a couple interesting slideshows chronicling the growth of these spat over time from two of those experiments. Ever wonder how fast oysters grow? Observe…
This is a time series from our first spat tile experiment, which you can read about in this post. As you may recall, this experiment was largely a failure because the adhesive we used to adhere the spat was inadequate. However, we decided to keep the fully caged tiles out on the reefs to see how they fared over time in different locations. I photographed the tiles every 6 weeks or so, so that we now have a series showing their growth over time. The slideshow shows one of the tiles from Jacksonville. It starts in October of 2010. You’ll notice that not much growth occurs though the late fall and winter, but the spat start to grow noticeably from April-June 2011. From June-September the spat grow explosively and many new spat settle on the tile from the water column and grow equally rapidly. Just as plants (and algae) have a summer growing season, so too do the oysters that feed on them, when conditions are warm and there is abundant phytoplankton in the water to eat.
Next is a series of images from our caging experiment last summer, which you can read about here. Our large cages contained either:
no predators (bivalves only),
spat-consuming mud crabs and oyster drills (consumers),
or mud crabs and oyster drills plus blue crabs and toadfish (predators).
The spat tiles within the larger cages were placed either exposed to potential predators or protected from them in a smaller subcage. Here are typical examples of what tiles looked like at the end of the experiment (about 2 months after starting). You can see how all the spat on the unprotected tiles were wiped out in the consumer treatments, but a good number survived in the treatments with no predators, as we would predict. In the predator treatments, most of the spat on unprotected tiles were removed, but not as fully or quickly as in the consumer treatments, which we would predict if the predators are inhibiting consumption of spat by the mud crabs and drills through consumptive or non-consumptive effects. You’ll see one tiny spat holding on in the predator tile shown. On the protected tiles, most of the spat survived in all treatments, as expected. We plan to further analyze the photographs from the protected tiles though, to see whether spat growth rates differed between them. We may find that protected spat in the consumer treatments grew slower than in the other treatments because of non-consumptive predator effects.
Currently, we’ve recovered most of our arsenal of spat tiles from the field, and I say we have probably amassed enough bricks to pave an entire driveway! Good thing we can reuse them!
The Biogeographic Oyster Study is funded by the National Science Foundation.
A hardhead catfish, one of a mud crab's primary predators on North Florida oyster reefs.
As 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.
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!
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.
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.
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!)
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.)
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.
As 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.
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.
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 RogersFSU Coastal & Marine Lab
Beautiful, isn't it? But working on oyster reefs in Jacksonville hasn't been as nice as its sunrises.
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.
The small cages in the photo above were used in an experiment I conducted to study California oysters. The insanely large cages in the photo below are from an experiment designed for our insanely large biogeographic oyster study.
While we had planned to install only 18 of these cages along the Atlantic coast of Florida, my crew wound up installing 70 cages over about six weeks. How did we reach such inflation in the number of cages and amount of digging? Well, it mainly stemmed from my ignorance of this area and the St. Johns River, which happens to dump a lot of sediment around oyster reefs. Because this sediment is deep and flocculent, it’s dangerous and almost impossible to work in. In fact, I may design a new study to analyze how oyster reefs manage to keep themselves above this ever-growing mud pit. I digress.
Relative to the abundance of these un-workable oyster reefs, mudflat areas suitable for our new experiment (i.e., near oyster reefs and firm footing) are quite rare. It was our luck (for better or worse, as you will soon read), we stumbled upon a sufficiently and suitable mudflat north of Jacksonville. After three days of hard digging, we managed to create large cages ready to support our experimental treatments. Suspecting that this site seemed too good to be true, we left the cages to fend for themselves for a week. If we returned to discover no problems, then we would proceed with the experiment.
On to St. Augustine- fitting the theme of bigger not always being better, our gargantuan stone crabs burrowed out of cages we had installed there. Even worse, cages without stone crabs were coming out of the ground because they were not dug in deep enough. The stone crab problem represents another example of why I should always run pilot experiments before attempting anything ambitious. Unfortunately, I have not learned this lesson yet. Or, I seem to periodically forget it.
Because I lacked the time to run such a pilot experiment, I ditched the troublesome stone crabs. We then awoke at dawn for the next three days to re-install cages (see the video below) in an over-kill sort of way. For this task, we took digging deep to a whole new level. Nothing was going to get inside or out of these cages without our permission. You can see how much deeper the cage bottoms extended into the ground by looking at the same cage pre- and post- renovation.
Having weathered the St. Augustine mishaps, we confidently headed back to Jacksonville to assess those cages. Upon arrival, I was subjected to a horrific scene: three days of hard labor undone by high flow conditions.
Note to self: mudflats are firm because flow is too high to allow sediment accumulation.
Stubbornly, I decided to force my will upon Mother Nature by digging cages in deeper and reinstalling them at locations behind marshes that would presumably buffer flow. Lacking the time to test this new cage installation, we immediately installed experimental treatments. This leap of faith was necessary in order to stay on schedule with the NC and GA teams.
Okay- cages up, reefs in, bells and whistles turned on. Afterwards, I raced back across the state to help two interns on their projects. Halfway back across the state and late on the Friday of Memorial Day weekend, I managed to blow the old lab truck’s transmission. As if getting a tow truck to Lake City at midnight wasn’t hard enough, getting one that would tow our truck and our kayak trailer was highly unlikely. But, taking pity on us, a wonderfully nice tow-truck driver agreed to load the trailer onto our truck.
Meanwhile, team Georgia was also experiencing problems with flow, sedimentation, and misbehaving predators. In short, we were throwing everything at this experiment and making little progress. At this point, ironically, the relative slackers amongst the three teams- the slow-to-start NC team- moved into first place- the horror!
After the passing of one mercifully tranquil week, we headed back to St. Augustine to check on things and collect data on our tile experiment. Interestingly, the experiment was working and we observed some variation in how predators indirectly benefit oysters; the positive effect diminished with latitude.
But then back again to Jacksonville- destroyed cages followed by some extremely colorful language. There should not have been deep pools of water surrounding the cages at dead low tide.
Obviously, it was time to cut our losses by not messing around with this site anymore. As a result, we spent the next three days searching all of northern Florida and southern Georgia to find a new ideal study site: suitable to oysters, no quick sand, firm footing and modest flow. After three days of intensive searching, we can confidently claim that such a site does not exist.
After accepting that this experiment could not be conducted in northernmost Florida, we decided to redirect Jacksonville resources to St. Augustine. There we would conduct a similar experiment that focused on a predatory assemblage unique to Florida: stone crab, toadfish, catfish, and crown conchs. So, nine more cages, nine more experimental reefs, and all the associated bells and whistles were established once again. By this time, my crew felt that they could easily serve in the Army Corps of Engineers.
Although things are now going well and we have a much better understanding of how to initiate this type of an experiment, my general ignorance has kept a Florida State University intern in St. Augustine for 7 weeks after agreeing to be there for only two weeks. Ooopsie!
Stay tuned in for a Hanna update on St. Augustine’s crown conchs and a post from Tanya about the summer madness from a technician’s perspective.
David’s research is funded by the National Science Foundation.