In many of our previous posts, we focused on how predator patterns may dictate why oyster reefs look different from NC to Florida. While a cursory look at results thus far supports this hypothesis, we’ve yet to consider alternate explanations. And failing to consider alternatives would not be very objective or scientific. After all, our job is to collect a lot of data and perform a lot of experiments that could possibly refute our predator hypothesis. Only by surviving all of these data and tests can our hypothesis gain strength, and of course it can never be proved. Continue reading →
The photo above is my work computer’s desktop picture. Most of the time, when people see it, I find that they had no idea what an oyster reef looked like. One coworker thought it was a muddy cabbage patch. To be honest, until I first stepped on one for this project, I wouldn’t have known a reef from a pile of rocks. And, like a lot of people, I love eating the things- right out of the shell with a little grit and juice. That’s the disconnect we sometimes have between the food we eat and from where it comes. So it occurred to me that, while we’ve been talking these last few months about the complex relationships between predators and prey on the reef, it might be helpful to get back to oyster basics. Over the following weeks, we’ll cover various topics (like why subtidal oysters are harvested more often than intertidal ones like those up there). We’ll start with what it’s actually like out on a reef, and what you’d see there.
The following photos are of samples taken at each of Dr. Kimbro’s sites, as mentioned in his previous post. After surveying the reefs to see what large fish and crabs were living in the reefs, he and his team turned to looking at the oysters and the creatures living under them in the mud. That’s what you’re seeing here. Click on any photo to make it larger.
As my assistant Tanya eloquently wrote in our last post, our July efforts produced interesting data on the predatory fish and crabs that hang around oyster reefs from North Carolina to Florida.
Cedar Key reefs, like the one above, tended to be sparser with slightly larger oysters than those in Alligator Harbor
After working on our sleep deficits, we dialed up some Willie Nelson on the iPod and were on the road again during the second week of August. Our goal: to determine if predator patterns on oyster reefs from NC to Florida were associated with any patterns in oysters (e.g., number and size) and smaller animals that both use oyster reefs as habitat (e.g., polychaetes and crabs) and as food (e.g., crabs).
This destructive sampling involved ripping up large sections of our reefs and placing them in large bins while trying to prevent any crabs or other critters from falling out. Because these are marine organisms, we had to work fast and quickly get them into a temperature-controlled room (50 degrees F) back at FSU’s Marine Lab. Easy when collecting samples from nearby Alligator Harbor, but not so easy when collecting samples at our other three sites in Florida.
But before dashing back to the lab, we deployed some instrumentation and took lots of sediment and water samples (more about this stuff later). Then, the race to keep our samples fresh commenced and mostly occurred on I-95 and I-10; I’m still seeing lane dividers and road reflectors when I close my eyes at night. After a few hours of sleep, we would drive back across the state to another site and start the process all over again. All of this sleep deprivation and highway racing against biological clocks made me feel like I was Smokey the Bandit boot-legging some Coors Beer across state lines (maybe I’m showing my age here, but a classic movie nonetheless).
Luckily, we had some great volunteers to help process these samples back at the lab while I was out ripping up oyster reefs, because processing each sample took a long, long time.
Liz and Hanna sort the reef samples.
After a week and a half of sample processing, it was really cool (or so I hear, because I was mainly on the road) to see all the animals living within the oyster reefs and how they and the reefs themselves differed from site to site. For instance, Alligator Harbor seemed to have dense reefs of small oysters while Cedar Key had sparse reefs with slightly larger oysters; both had few mud crabs (maybe due to the abundance of big fish?). We also noticed that animals north of Jacksonville must be on growth hormone supplements because everything is gigantic (bigger mussels, bigger crabs, and bigger oysters). Meanwhile, the crown conch population in St. Augustine is huge and appears to be mowing down the oysters. So, now I have new side-project: why are crown conchs an abundant nuisance for oyster reefs in St. Augustine but not at other sites?
From one week of field work, we now have about a month or so of associated lab work that will involve counting, measuring, and identifying every organism. I’m really excited to see how all the predator, intermediate consumer, and oyster reef data correlate from estuary to estuary.
David’s research is funded by the National Science Foundation.
As Dr. David Kimbro’s research assistant, I help out with all aspects of the biogeographic oyster project in the field and at the lab. David, myself, and Evan Pettis (an intern from FSU) have returned from our big sampling effort to characterize the predator community on the oyster reefs at our chosen field sites. Over the course of a productive yet exhausting week, we successfully deployed and retrieved nets and traps at Alligator Harbor, Cedar Key, and St. Augustine and found very interesting differences in the abundance and diversity of fish species between sites. St. Augustine had by far the greatest diversity of large fish species, including redfish, snapper, toadfish, flounder, jack, ladyfish, bluefish, and menhaden. At Cedar Key and Alligator Harbor we caught longnose gar, a fascinating and very ancient fish with extremely hard scales and a long toothy snout. The largest fish we encountered were black drum, which we only captured at Cedar Key. Pinfish, hardhead catfish, and striped mullet were present at all of our sites, although in varying abundances.
Although we’ve busied ourselves this summer by selecting research sites and practicing various aspects of our sampling program, we have still not collected any ‘real’ data concerning the objectives of our biogeographic oyster project. Well, this post will be short because as I write this we are hectically preparing to begin said research. Coincidentally, tropical storm Bonnie has also decided to begin her work in the Gulf at the same time!
After all the time we’ve spent on oyster reefs, we thought it would be interesting to take a look at what the little guys mean to us culturally. The video above is from Our Town, Apalachicola and features the famed oystermen of that town. The article below is a little more personal.
Roberto Diaz de Villegas WFSU-TV
We had just finished interviewing John Spohrer for a photography feature and, well, we were in Apalachicola. So I decided to conduct what our oyster researcher Dr. David Kimbro would call an exercise in predator-prey relationships. My prey was some of Apalachicola’s finest product, and it wasn’t even an R month. Me and my wife Amy (who is also my production co-conspirator) decided to try a place with a decent-sized crowd of friendly locals out front, the Hole in the Wall. Amy did not eat any oysters and this was her last shoot with me for this project. More on that later.
People in Apalachicola are proud of their product. The man shucking the oysters behind the bar would excitedly declare “Oh, that’s a good one” as he picked them out of the ice. The perpetually smiling waitress who brought them to the table would come by every once in a while and ask “How do you like your oysters?”
“They’re delicious,” I’d say.
“Enjoy them while you can…”
Dr. David Kimbro in Alligator Harbor
I did enjoy them, as I have for years. People in these parts have for quite a while. Longer than you may realize. At nearby St. Vincent Island, ancient oyster shells and pottery shards lie in piles called middens, evidence of a long disappeared people. The shells have been dated at 4,000 years old or older. This means that people have been enjoying these oysters for thousands of years. It’s an impressive legacy, especially when you consider how some of our country’s other historical oyster producing areas have fared over time. The Chesapeake Bay used to be difficult to navigate it was so cluttered with reefs. New York City used to be renowned for the oysters harvested there, they were a staple of the Big Apple until just under a century ago. But while those habitats have been decimated, Gulf oyster reefs retain their abundance and quality. When we accompanied David Kimbro on the first day of his study in Alligator Harbor, the scientist who had been studying reefs in North Carolina and California marveled at the size of the reefs. He’d never seen so many.
I fell like I was rubbing it in Amy’s face eating those oysters, even if she had been looking forward to enjoying the local seafood as much as I was. We had done the research and shrimp were an acceptable food, rich in Omega 3 fatty acids important to brain development in embryos. This was her last shoot, as the days were growing hotter and we spend some long days on marshes and reefs. Our child will be born a Floridian, like I was. I’ve been spoiled by great beaches, a steady supply of fresh seafood, wetlands bursting with animal and plant life. I wonder in what kind of Florida my child will grow up. Will he or she have at their disposal what Floridians have had over the last few thousand years? No one can really say. Even if the worst happens, there is hope that we can restore it, even if it could never be exactly the same. In the meantime, I’ll just do what I was told. I’ll enjoy it while I can.
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See David and his crew in action, and see what animals are on Alligator Harbor reefs.
The title of this blog (a sports metaphor) is how my teacher first introduced me to marine ecology. For our oyster project, this essentially means that we need to establish who is on the oyster reefs before we can begin to make connections among predators, oysters, and their water filtration services….as well as (unfortunately) the impacts of oil.
So far, we’ve identified the organisms on the bottom rung of our food web (think of it has a pyramid): oysters, clams, amphipods, and polychaetes on the bottom rung of the food web and mud crabs and snapping shrimp on the next higher rung of the food web. Our goal this week was to begin quantifying who is at the top of this food pyramid. To do this, we deployed crab traps, bait-fish pots, and gill nets onto each of our reefs during low tide. Following the ensuing flood tide, we returned the next day to count our catch and then promptly release everyone.
the hardhead catfish was the most abundant species trapped during this survey
But after running out of fresh water to drink and profusely perspiring all the moisture out of my body while out on the reefs, it dawned on me that nature of this catch is likely an interesting seasonal pattern (again, I’m new here!): only hardy organisms that can tolerate really hot and low oxygen waters are going to be on Florida reefs right now. Once the rest of this research team begins collecting similar data from Virginia to Florida, it will be interesting to see if these low abundance-diversity patterns might last longer in some areas (e.g., Florida with longer summer) than in others (e.g., NC with shorter summer). If that’s the case, then the cascading effects of higher order predators (things at the top of our food web) down to oysters and their water filtration services may be occur more consistently during the summer in northern than in southern estuaries.
Hmmm…..good thing we are conducting a relatively long-term study and will consistently repeat this sampling in the future to rigorously detect interesting patterns like this one.
Until next time…
The Music in the video was by Jim Crozier. As always, we welcome submissions from local musicians. WFSU’s kayak was provided by Wilderness Way.
David’s research is funded by the National Science Foundation.
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Think a little smaller than this pelican here. Obviously, pelicans are a symbol of our coastal areas, flying in those long rows as they do while we’re driving down Highway 98. Pelicans covered in oil have become the poster-species of the environmental toll of the Deepwater Horizon oil spill. It’s horrifying to think of animals as evolved as dolphins washing up on the shores, and people of course are always concerned about sea turtles. As they should be. They are all important parts of the Gulf ecosystem.
But they are not the only important parts. There are other creatures that probably won’t make it on to that oil spill tragedy poster because, let’s face it, they already live in muck. Those are the species that we’ve been most concerned with on this site. They are worth worrying about, and I’ve come to find them cute in their way. I keep thinking I need to try to get Disney to make a movie based in a salt marsh or oyster reef, where mud crabs and periwinkle snails sing and hide from predatory blue crabs (who, like those sharks in Finding Nemo, might be sympathetic characters themselves). When kids are carrying plush fiddler crab dolls, maybe the little guys would get some consideration. As it turns out, however, I have no pull at Disney. So I’ll just talk about them right here on this blog.
Like the fiddlers. They eat sand. They shovel it in their mouths with their smaller claws, while they do the mating dance for which they’re better known with their larger “fiddle” claws. I see thousands of them at a time in a salt marsh, always scurrying away and making that sound, a little bit like trickling water and a little bit like tiny bubble wrap being popped. Of what importance are these silly little guys?
Fiddler crabs are crucial to the survival of a salt marsh
Other than being food for blue crabs, their importance has to do with the muck in which they live. They live in the sediment collected by the cordgrass root system; you can see the holes they call home throughout the marsh. As Dr. Hughes explained in this video, these burrows provide oxygen to the soil in which the cordgrass grows. So their presence helps the cordgrass grow, just as the cordgrass provides them shelter.
So maybe the fiddler crab hasn’t found himself at the center of any teary oil spill montage. But he’s an animal, and a fairly popular pet. Spartina alterniflora– aka smooth cordgrass- may never gain a foothold in the popular imagination proportionate to its ecological importance. It is the foundation species of a Gulf salt marsh. These marshes act as a filter for pollutants flowing into the ocean, protecting important estuaries such as those at the mouth of the Apalachicola River. Marshes provide shelter to a number of commercially important species (shrimp, mullet, and blue crab, for instance). And marshes also help absorb storm surges and prevent erosion.
Those are just a couple of examples. There are, of course, more. Tasty, tasty oysters filter water and prevent algal blooms lethal to other species. Toadfish have faces even other toadfish may not love, but they eat animals that would decimate oyster reefs if left unchecked. Those oyster predators are interesting as well. Mud crabs might get as large as 4 cm and have these thick little claws which tear through oyster shells. Oyster drills are small snails whose tongues (radula) are covered with thousands of small razor-like teeth.
As we move forward with this project, we’ll see more and more of all of these coastal denizens. So far oil has not reached the areas Dr. Hughes and Dr. Kimbro are studying, and so there is always hope that they may be spared. If oil does arrive, many of these species could be severely affected. And while some of them may not look like much, the harm that would come to them would have repercussions felt beyond their own habitats.
This snail lives on an oyster reef
Interested in seeing a fiddler crab plush toy as a WFSU-TV pledge premium? Well, that isn’t likely to happen. But we will take comments and questions, as usual.
Why is Dr. Kimbro selecting smaller reefs to study? How big is a mature oyster? Watch and find out.
In my previous post, I outlined my original reasons for being out on the reef. Although I’m still pursuing those goals, my lab is currently busying itself on the reefs with some newly formed research goals. Anticipating the arrival of oil, we’ve scrambled a lot over the last few weeks to come up with questions and methods that will allow us to understand how the oil affects oysters as well as the assemblage of other important species that it supports.
Using kayaks, David and his crew moved more easily about Alligator Harbor
Step number one in gearing up to study the impacts of oil and to launch our original project involved figuring out a better way to transport a lot of people and gear out to the reefs during low tide, where shallow water prevents boating and deep mud prevents walking. My lab now uses a fleet of kayaks to zip around all the oyster reefs within Alligator Harbor, which sure beats sitting in highway traffic.
Now, once you see our study reefs (patchy, small and next to marsh), if you are a local, you must be thinking that we’re crazy for sampling these puny little things instead of the massive mudflat reefs that are more isolated from the marsh. And I wholeheartedly agree. However, my other colleagues studying oysters in VA, NC, SC, and GA don’t have big massive reefs like these anymore thanks to a much longer and more destructive history of harvesting, dredging and disease. So, to complete our original research goals and to compare things among many different estuaries, we are using the lowest-common-denominator reefs among all of our estuaries: hence the small and patchy little reefs we selected.
Ok, now we’ve figured out how to access our sites and we’ve selected our reefs. Although the latter sounds simple, it’s actually been pretty messy: kind of like my first trying to walk out to the oyster reefs in Alligator Harbor! Using global positioning system (GPS) and Google maps, my colleagues and I have been remotely weighing in on which reefs to use based on whether particular reefs are too large, too small, too close to the ocean, too far from the ocean, exposed to too much harvesting pressure, or exposed to too much pollution. Again, in order to learn how similar food webs operate and affect oyster reefs differently over long distances, we need to make sure that we are comparing apples to apples, not apples to oranges or young oyster reefs (nothing but small oysters) to old oyster reefs (nothing but large oysters) or polluted oyster reefs to pristine oyster reefs.
Over the past week, we’ve not only selected oyster reefs within Alligator Harbor to be part of our original oyster study, but we also set up additional oyster reefs to study the impacts of the oil spill. This involves permanently establishing areas within reefs that are censused for the number of dead and living oysters before the oil hits. Then, when the oil hits, we determine if the number of dead oysters increased.
But, even if we see more dead oysters than live oysters in the future, how do we know whether the oil (rather than some other factor) was the cause?
Well, we are also taking water, sediment, and oyster samples to be processed for stable isotopes. In short, chemical elements (e.g., Carbon, Nitrogen) exist in different forms (i.e., isotopes) and oil hydrocarbons have a Carbon isotope that can be used like a fingerprint.
So, we are also sampling the environment (water and sediment) and the whole food web centered on oyster reefs to determine background levels of oil. Then, when the oil hits we should see a tremendous increase in a new oil signature (that from the Deepwater Horizon spill) that coincides with negative impacts on oysters.
But, in addition to oysters themselves, we are also interested in the predators and prey that it supports. Because we do not yet have a lot of data describing when and how many predators and prey are around and because there is no way to get that data in time before the oil arrives, we are using other stable isotopes to quickly describe how predators and prey are organized within the oyster food web: who is eating whom. The isotopes of Nitrogen are good for this because the form of Nitrogen changes as it passes up the food web from things like oysters to things like big crabs and fishes. So, our second new question is… who has been eating what and how does this organization, which took a long time to develop, change immediately and a few years after the oil spill? Pursuing this new goal has involved some pretty fun hunting of all sorts of critters that make up the oyster food web such as amphipods, polychaetes (worms), clams, mussels, mud crabs, snails, blue crabs, stone crabs, and fishes. We just finished sampling Alligator Harbor and are now off to do the same things in Cedar Key, St. Augustine, and Jacksonville.
Because these four sites in Florida will likely experience much different levels of oil, we will be able to learn how much oil is required to negatively impact oyster reefs and the community of animals that they support.
David’s research is funded by the National Science Foundation.
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