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.