Tanya Rogers was Dr. David Kimbro’s research assistant and worked primarily on the collaborative study of oyster biogeography and ecosystem processes featured in this blog. She has a Bachelor of Science in Biology from the University of Puget Sound in Washington, and has done undergraduate research at Bodega Marine Laboratory and Friday Harbor Laboratories. She is interested in marine community ecology and conservation, as well as natural history and scientific illustration. She is now a graduate student for Dr. Kimbro at Northeastern University.
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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.
“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.
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.
Although the oyster project’s fieldwork has attracted most of the attention on this blog (indeed, it is where most of the action happens), our time at the lab deserves a bit of discussion as well, as much progress on the oyster project also happens behind walls. This is especially the case nowadays, in the winter, when fieldwork is kept to a minimum on account of weather and the general inactivity of animals on the reefs. What better time to catch up on processing the zillions of samples we’d collected over the past many months, but never quite had time to get to.
Labwork is a whole different beast than the energetically-demanding, volatile nature of fieldwork – I wouldn’t go so far as to call labwork boring, but it is often incredibly repetitive, time-consuming, and demanding of extreme patience. It’s certainly not as exciting, sensational, or enjoyable as fieldwork (in my opinion), but it is just as much an integral part of the science, and anyone who goes into research will probably spend much of their time sitting at a bench, repeating the same procedure twenty-thousand times in pursuit of the great dataset (that is, until you hire techs and grad students to do it for you). Yet labwork has an appeal and mystique all of its own that’s not to be overlooked.
Certain tasks in marine biology necessitate learning skills used in commercial seafood. Here, Tanya shucks an oyster to remove the meat and weigh it.
So while David retires to his office and catches up on the uncountable tasks at hand there, I’ve holed up in the lab and plodded steadily through the several hundred samples of ours waiting patiently in the freezer. Lately, this has involved two major tasks. The first was to process the sediment organic matter (SOM) samples from our (and Jeb Byers’s) oyster reefs collected every 6 weeks since August. A total of 640 samples needed to be transferred from bags to aluminum dishes, dried for 3 hours at 105°C to evaporate any water, weighed, combusted for 3 hours at 525°C to incinerate and volatilize any organic material, and reweighed to determine the percent of the sediment composed of organic material. This analysis will allow us to compare how oysters affect the amount of organic material in the sediment across latitude. In case you ever wanted to know, 525°C (977°F) is pretty dang hot, and the smell of burning sediment that wafts down the hall during the first half hour or so in the furnace apparently smells exactly like an electrical fire.
Mmmm... oyster jerky!
My second task was to process samples of oysters we’d collected from our reefs during our intensive August surveys. After thawing them out, this involved measuring the total weight, wet and dry tissue weight, and various shell dimensions of 400 individual oysters. From these data we’ll be able to calculate an oyster condition index (health indicator), which we’ll be able to compare across sites. Obtaining wet and dry tissue mass required removing and weighing the meat (my oyster shucking skills increased greatly after this exercise), and reweighing it after drying for 48 hours at 70°C (this generated some quite odorous and not-all-too-appetizing looking oyster jerky). Between the sediment and oyster samples, I admit I had a monopoly of the marine lab’s drying ovens for a short while. I can say though that sticking your face in a drying oven is a great way to warm up on a cold winter’s day.
There are a variety of ways researchers try to liven up the tedious nature of labwork. Many listen to music or books on tape, or play movies in the background, or chat with labmates if others are around. Sometimes I’ll do these things, but other times I find the quiet monotony of labwork to be rather peaceful. There’s no stress or distractions or real need for thinking – just you, the calipers, the oysters, the datasheet. You kind of get in “the mode” and it can be rather, I don’t know… zen? At least for a little while. It’s a nice contrast to the intensive and unpredictable nature of science in the field.
David Kimbro’s research is funded by the National Science Foundation.
(Editor’s Note. Although David refers to Randall’s participation on this study, her role was not elaborated upon in this video. That will be a part of the next video, on David’s collaborators, as Randall is David’s Co-PI- or Primary Investigator)
Tanya measures a fish caught in a gill net.
It’s been said that research techs are those who do the dirty work in science. Although true in many ways, I love being where the action is, collecting the data, turning ideas into reality. That said, here is some of my perspective on what went into our October trip and what days in the field were like.
A busy field trip like our October sampling push typically takes at least as many days to prepare for as the length of the trip itself. Although the daily blog posts covered our time in action, David and I spent most of the previous couple weeks just planning for this trip so that it could run as smoothly as it did. I feel it worth mentioning the many hours I spent pouring over tide charts and editing and re-editing our complicated schedule so that we could accomplish everything as efficiently as possible, factoring in all manner of time and tidal constraints, travel time, land and sea transportation, overnight stays, and numerous other variables, plus designing it with enough flexibility that we could adjust our plans in the field at a moments notice (and indeed we did). In addition to scheduling I also had to make sure we had all the materials we needed to for our trip, that those materials were all in working order, and that they are all packaged up accordingly and conveniently in our two vehicles. The last thing you want is to be out in the field and realize you’re missing some critical piece of equipment.
As they conduct these initial sampling trips every few months, they keep finding new and interesting species living in and around the reefs. Here, Tanya is taking measurement of one of her favorite finds of this last trip, a striped burrfish.
Out in the field, going to retrieve our traps and nets is always the most exciting for me, since you never know what we’re going to catch, and I was interested to see how the October fish community compared with that of July. We caught a few new fish species in our traps this round, including a beautiful spotfin butterflyfish (Chaetodon ocellatus), juvenile snapper (Lutjanus sp.), and a couple tiny pufferfish (technically striped burrfish, Chilomycterus schoepfi – they were very adorable). Equally exciting was getting to use the new motor on our skiff for the first time at our sites. Although noisy and bizarre-looking, it performed admirably in shallow water, as it was designed to. At least in terms of temperature and humidity, conditions on the reefs were considerably more pleasant for us than during the summer. It was wonderful not to be wiping sweat from your face every 10 minutes. The dramatic increase in the no-see-um population at dawn and dusk was not so pleasant however, as David has duly noted. The dawn low tide at Jacksonville brought the worst swarms we’d ever encountered in the field. Incredibly irritating both physically and mentally, they made work nearly impossible, and forced me to spend the subsequent week covered in uncountable numbers of ravenously itchy welts.
Despite its exotic look, the spotfin butterfly fish is a native of both the Gulf and Atlantic coasts of Florida.
When not out on the reefs, there was rarely a moment when something didn’t need to be done – whether filtering water samples, rinsing gear, or (most frequently) extracting spat. Our only breaks seemed to be for the necessities of eating, showering, sleeping, and making coffee. (For David, coffee appears to rank just below data and samples in terms of his most valued possessions in the field.) Our biggest and most time-consuming challenge was whether we could get all of the spat extracted and tiles made for our predator-exclusion experiment in the time allotted between netting and trapping. The process of isolating spat was incredibly tedious to say the least, and particularly frustrating when, after you’ve been working on a spat for several minutes, your tool slips and the spat gets crushed, or it flies across the patio, never to be seen again. You couldn’t help but feel the spat always picked the most inconvenient places to settle. It was also quite a messy process, with water and oyster bits flying everywhere and various crabs skittering across the counter. The oysters also love to slice your fingers open during the few moments when you neglect to wear gloves. Yet in spite of the tedium, we couldn’t help noticing new and interesting critters living amongst the oysters as we broke them apart. For instance, we noticed considerably more porcelain crabs (Petrolisthes sp.) and Boonea impressa (a small, white snail that parasitizes oysters) than we’d seen in previously collected oyster samples. We also found an oyster pea crab (Pinnotheres ostreum), which lives on and steals food from the gills of oysters, and a number of dark brown cylindrical mussels (Lithophaga bisulcata) that bore into the calcareous shells of oysters. It always amazes me how many different animals can be found living within the structurally complex habitat created by species like oysters.
Young oyster spat, beginning their new careers in science.
I remember on one of the last days of our trip, I kayaked out to our St. Augustine reefs for a final service and check while David finished up the dremeling. I remember looking upon reef #5, seeing our newly deployed, spat-covered tiles and cages, our cleaned tidal data logger housing, and our newly replaced spat stick, arranged so neatly on our marked reef, and feeling delighted at our accomplishment, knowing how much effort has gone into this setup. I remembered that in my position it’s easy to get sucked into the details, but it’s equally important to remember the big picture, and how this research will contribute to our greater understanding of oyster reef ecology.
After our field trip, as we recover from battle wounds and wait for the mud to work its way out from under our fingernails, work on the oyster project continues at the lab. For me this has meant entering lots of data and starting to process our many samples. Before you know it though, it’s time to start to preparing for our next journey onto the reefs and the adventures that await.
The Kimbro, Hughes, et al. biogeographic oyster study is funded by the National Science Foundation.