Where did my winter of catching up on work go? And why is spring quickly hurtling into summer? YIKES!
…Okay, I feel better. All of us here feel a little behind on things, because this past winter and spring have been full of other projects (in addition to the oyster one) such as investigating how the oil spill affected marshes throughout the west coast of Florida and examining what all of those snails are up to out on Bay Mouth Bar. But now that summer is almost upon us, it’s time to move all hands on deck back towards the ambitious summer oyster goals.
Environmental vs. Predator Effects.
To lay the ground work for this summer’s oyster research, I spent a few days in St. Augustine, Florida, which is where we will conduct our colossal field experiment. As a recap of the oyster objectives, we spent year 1 monitoring the oyster food web at 12 estuaries between Florida to North Carolina. Well, we found some cool patterns regarding the food web and water-filtration/ nutrient cycling services on oyster reefs (see the 2010 wrap-up). So, now we want to know what’s causing those patterns. Are differences in oyster reefs between NC to FL due purely to differences in water temperature, salinity, or food for oysters (phytoplankton)? Or, do we have a higher diversity of predators down south that are exerting more “top-down” pressure on the southern reefs? Or, is it a combination of the environment and predators? Continue reading →
It kind of looks like one of those vintage ’80’s jackets adorned with mirrors and sequins- mollusk style. This horse conch’s got a little bit of everything on it, the result of an interesting reversal of roles in this seagrass bed on Bay Mouth Bar.
If you’re a regular reader of the blog, you’ll realize that we often talk about similar research questions or ideas in the context of different projects. As David mentioned in his description of the Baymouth Bar project, this overlap is usually intentional: as ecologists, we’re interested not only in the specific habitats that we study, but also in the underlying factors that affect these habitats and the valuable services that they provide to we humans.
It may appear at times that we’ve been covering a diverse array of topics, and while this is true, all of these topics are interconnected- a web of topics centered around a couple of central themes. The diagram below is the map that shows where every post-topic fits into these central themes. Even the artists, writers, and photographers we occasionally feature have their place amongst ecological processes like sedimentation and the non-consumptive effects of predators. Every post from here on out will have one of these icons on it- if you don’t know what the icon means, just click on it and you’ll be back at this figure with an explanation:
Dozens of different mollusk species interact within a relatively small area at Bay Mouth Bar, from all manner of bivalves to the predatory snails that eat them (and each other).
As soon as you arrive to BMB, it is easy to imagine and feel the same curiosity and fascination that Robert Paine brimmed with when he first immersed himself in the sand bar fifty years ago.
If someday you have the opportunity to visit BMB at low tide, then you would receive much pleasure in looking at 40000 m2 of sand, full of awesome critters! Twenty minutes by kayak, that’s it!
Since I started working at FSU’s marine lab, I have frequently cast longing looks at a local study system that hasn’t been examined in over 50 years. Back in the 1960s, the world’s most famous ecologist (Bob Paine) was a post-doctoral researcher working at FSU’s Marine Lab. It was at this time and place where he began developing some of the concepts that would transform the field of ecology. Continue reading →
David's collaborators, from left to right- Dr. Jeb Byers, Dr. Mike Piehler, Dr. Jon Grabowski, and Dr. Randall Hughes.
As you can see from the video that summarized our efforts over 2010, it was a busy 6 months of research. After taking a great break during the holidays, the entire oyster team (Jon = Gulf of Maine Research Institute, Mike = University of North Carolina at Chapel Hill, Jeb = University of Georgia, Randall = Florida State University and me) met for a long weekend to figure out what we accomplished and where we are going in the future.
You might think that our 2011 research plans should already be set given that we received funding. Well, we did receive funding to carry out some outlandish field experiments in 2011, but these experiments were dreamed up in our offices and may not address the most ecologically relevant questions for our system. Checking in with the monitoring data is probably the best way to determine if our planned experiments were on target or if they needed to be adjusted and hopefully simplified!
Prior to the oyster summit last weekend, I hounded all of the research teams for all of their data. Given the huge volume of data and everyone’s busy schedules with teaching classes and other research projects, this was quite the task. Once Tanya meshed all the data together (also not a simple task), I then moved on to the next task of analyzing our data.
Well, the initial excitement quickly turned into a stomach churning feeling of….where the heck do I begin? Similar to the way that too many prey can reduce the effectiveness of predators, the data were swamping me…I was overwhelmed and the draining hourglass wasn’t helping (people were flying into town in two days…yikes!).
After multiple cups of coffee, the anxiety passed and I decided to revisit some basic questions:
David's team used gill nets to catch the larger fish around the reefs, many of which are top predators in that habitat.
(1) With the gill nets, we obtained predatory fish data. So how do the abundance and biomass of these fishes vary across latitude? And does this pattern change with season (i.e., summer versus fall)?
(2) Then I thought back to the fond memories of ripping up oyster habitat to check out the abundance of things that consume oysters (e.g., mud crabs). Oh…the memory of that work gives me a warm and fuzzy feeling; I bet Tanya, Hanna, Linda and everyone else that helped feel the same way! How do the abundances of these things change across latitude? Are there larger crabs up north or down south? How does the mud crab picture mesh with the predatory fish picture?
This spat stick is made of calcium carbonate, the same substance as oyster shell, and is ridged to simulate the ridges in those shells. That makes it an attractive landing spot for oyster spat (larval oysters), which tend to settle on oyster shells.
(3) Working our way down the food web and sticking with the oyster samples we ripped up back in August, how do oyster densities and oyster size change across latitude and how do these patterns mesh with the mudcrab and predatory fish data?
(4) Finally, I wanted to revisit the data from our instrumentation to see how temperature and salinity changed across latitude and with season, as well as the data from our spat sticks to see how oyster recruitment differed.
It’s pretty amazing that six months of work can be summarized so quickly into four topics. Well, I kept hitting the coffee and got all of these data worked up in time for the first portion of our oyster summit. Surprisingly, all inbound flights arrived on time and we all assembled last Friday to go over the data. I’ll briefly lift the research curtain to illustrate what our data looked like:
The Georgia reef gill nets trapped a lot of sharks. Here Dr. Jeb Byers is removing blue crabs (also an oyster reef predator) from shark bellies. The trapping done on these reefs is clarifying the food web for these habitats.
(1) Although we predicted predator abundance to increase at lower latitudes, predator abundance and the number of different predators peaked in Georgia/South Carolina. This is because lots of the species we have in Florida were also in Georgia. And, Georgia has lots of sharks! Needless to say, Jeb’s crew has been the busiest during gillnet sampling. Jon and Mike’s crew have had it pretty easy (no offense)! The workload reduced for everyone in the fall, but the differences across latitude stayed relatively the same. The really cool result was the pattern that hardhead catfish are extremely important and the most abundant predatory fish on Florida reefs; I love those slimy things.
(2) Interestingly, mudcrab biomass peaked up north where predatory fishes were less abundant.
(3) And the abundance of large, market size oysters was highest where predatory fish were most abundant (GA/SC).
(4) Amazingly, we all did a good job selecting oyster reefs with equivalent salinities (this can vary a lot just within one estuary) and temperature was the same across all of our sites until December….instrumentation up north got covered in ice! Glad I was assigned the relatively tropical reefs in Florida. Finally, oyster recruitment in NC and Florida appears to proceed at a trickle while that of GA/SC is a flood-like situation during the summer.
A month after first being deployed, Tanya and Hanna inspect an Alligator Harbor tile. You can see that some of the oysters have definitely started growing, but also that some of the spat became unglued. When they run the experiment again, they'll use a different adhesive more suitable for a marine environment.
After we all soaked that in, we then talked about the tile experiment. While these data were really cool (mortality presumably due to mudcrabs was lowest where predatory fish were most abundant = GA), we worried about being able to tease apart the effects of flow, sedimentation, and predation. Unfortunately, this experiment seems to uphold my record with experiments: they never work the first time. We’ll probably repeat this in fall of 2011 with a much better design to account for flow and sedimentation.
Before breaking for a nice communal dinner at my place, Mike summarized the nutrient cycling (sediment) data that we have been collecting. In short, having lots of living oysters really promotes de-nitrification processes and our sampling picked this up.
Putting this all together, it looks like there are latitudinal patterns in fish predators that may result in mudcrab density and size patterns. Together, these may help account for latitudinal patterns in oysters (highest in GA). This all matters because more oysters = more denitrification = healthier estuarine waters.
END DAY 1
On day 2 of the summit, we worked through what made us happy about the monitoring data, what things we could add on to make us happier, and that we should continue this monitoring through the summer of 2011. This actually took all morning.
On day 2, the oyster summit moved into the more comfortable location of the Marine Lab guest house.
After a quick lunch break, we then reconvened in another room with a better view (nice to change up the scenery) to go over how we should experimentally test the linkages I mentioned above. This is where the saw blade of productivity met a strong wood knot. Personally, I became horribly confused, fatigued and was utterly useless. This resulted in lots of disagreement on how to proceed and possibly a few ruffled feathers. But nothing that some good food and NFL playoff football couldn’t cure.
After taking in a beautiful winter sunset over the waters off the lab, we ditched the work and began rehashing old and funny stories about each other.
Amazingly, we awoke the next morning and fashioned together a great experimental design that we will implement beginning June 2011. To Jeb’s disappointment, this will not involve large sharks, but we will get to play with catfish!
But now it’s time to prepare for our winter fish and crab sampling. It will be interesting to see what uses these reefs during the dark and cold of winter!
Thanks for following us during 2010, and please stick around for 2011 as I’m sure things will get really interesting as we prepare for our large field experiment.
David’s research is funded by the National Science Foundation.
Emily and Robyn setting up yet another tank experiment that I've dreamed up. (Thanks to Nancy Smith for the pic!)
Because of the big focus on oysters over the last month, it may seem as if we haven’t been doing anything “In the grass”. We’ve been busy, though, trying to squeeze in a few additional surveys and experiments in November before it gets cold enough that the animals stop eating (or eating very much, I should say) and the plants stop growing. For a while there, I was coming up with so many end of season ideas that I’m pretty sure my crew hated to see me coming! We just did finish up before the winter weather arrived (early) in December. (More on what it’s like working in this cold weather in future posts.)
We actually missed the opportunity to do one of our planned studies involving grasshoppers – there was a cold snap two nights before we went in the field to get the hoppers, and they were nowhere to be found. Those data will have to wait until next spring when the grasshoppers turn up again!
Snails climbing on cordgrass reproductive stems in the field.
A tasty snack for a periwinkle snail?
I’ve mentioned before on the blog that we noticed lots of snails climbing on cordgrass reproductive stems this fall. In collaboration with David and his team, we visited marsh sites along the Panhandle to see if our observations would be supported with rigorously collected data. So far, so good!
The trusty tank set-up at FSUCML.
We also started a series of experiments in our trusty tanks at the FSU marine lab to tease apart why snails may have this preference: Do the snails simply like that the reproductive stems are taller than regular stems? Or do the reproductive stems “taste” better because of greater nutrient content? Does it matter if predators are present or not? The preliminary results suggest that they like the reproductive stems, regardless of whether they are taller or not. In January, we’ll head into the lab to do the tests for nutrient content that should help us to tease apart why that may be.
2. Does needlerush provide a better predation refuge than cordgrass?
Needlerush (center patch) is typically much taller than cordgrass (surrounding area) in St. Joe Bay
Last fall I did a tank experiment to look at whether snails prefer to climb on another marsh plant species, needlerush (Juncus roemerianus), and whether this preference increased snail survival when predators were around. The results were interesting, but as usual, the first round of the experiment created additional questions that required more work. In November we started a similar experiment, again in the tanks at the marine lab, looking at snail climbing behavior on needlerush and cordgrass in the presence and absence of the snail’s nemesis, the blue crab.
Needlerush is naturally taller than cordgrass, so to test if this difference in height can explain snail behavior, we “experimentally manipulated” (in other words, used scissors to cut the needlerush down to a shorter height) needlerush height: some tanks have naturally tall needlerush, some have needlerush that is on average the same height as the cordgrass, and some have needlerush that is shorter than the cordgrass. Add a blue crab to half of the tanks, and voilà, the experiment is underway!
It’s a bit ironic that each of the experiments we recently finished converged on a similar idea – snails appear to prefer to climb on taller plants. Considering that the taller the plant, the farther they can climb away from predators in the water, it makes sense. The true question is to figure out whether and why it matters that the snails do this. If they climb on reproductive stems, are fewer cordgrass seeds produced? What will that mean for next year’s crop of cordgrass? Also, if snails spend a lot of time hanging out on needlerush to avoid predators, does that mean they don’t eat as much cordgrass? Knowing things as seemingly arcane as which plant a snail prefers to climb on can help us predict and manage the overall abundance and productivity of cordgrass, and the salt marsh in general. And of course, the field work and experiments are fun! Especially when you get to wrestle with blue crabs…
Here are some photos of periwinkle snails in Randall’s latest tank experiments:
Randall’s research is funded by the National Science Foundation.
(Farthest to nearest) Hanna, Tanya, and Cristina perform some of the more glamorous work of this trip- cracking oysters apart and finding spat (oyster babies). David needed everyone on his team to perform, or this week would be wasted.
A while back, I was talking to Randall or David, I forget which one, and they were telling me about building a research crew. Obviously you need people who have the knowledge and skills to do what needs to be done- from identifying fish to driving a boat, or setting a gill net. But just as important, they said, was that you had people you could get along with, since you practically live with them sometimes.
Weeks like this one are where building the team pays off. When you’re getting bitten up by gnats on an oyster reef at 6:45 in the morning, you don’t want a crew member sniping at another about losing a fish out of the gill net. David remarked to me that the morale of this team had stayed strong, despite the schedule always changing and everyone having to shoulder more of the load while David got the tiles ready. They did a lot of work on their own, and made it possible to get everything done even as plans shifted.
On a day like today, it was good that David has the crew he has.
A swarm of gnats hovers over the oyster reef water.
6:45 AM– Retrieved fish from nets, deployed traps.
After a night of battling cockroaches in their “haunted” house, they might have been happier to be out on oyster reefs at this early hour. They might have, had it not been for the no see-ums. They were getting eaten alive, which made it hard to work. And it got worse from there, as if the universe decided to pile it on in this last day.
As early as it was, the birds had gotten to their fish before they did and there were no stomachs to examine. And then there were the injuries. David cut his finger on a catfish spine, and then, within about ten minutes, a stone crab got a hold of Hanna’s finger and inflicted some pain. They’re both okay. Their truck, however, is a little worse off.
Banged up over the course of the week, the crew- and their truck- are ready to come home.
When they got back, they glued spat onto tiles one more time to deploy this afternoon.
3:00 PM– Tanya, Hanna, and Cristina retrieved the traps and set the tiles.
7:00 PM– The girls headed back to the FSU Coastal & Marine Lab. When they got there, they cleaned all of their gear, even though it was late. They figured that it was better to wash the salt off sooner than later.
So that was the week. They’ll go back to each of the sites about every six weeks, though it won’t always be this intensive. David, Jeb (SC/ GA), and Jon (NC) will start to see seasonal patterns in the fish that they find- when do certain fish tend to show up on what reef? They’ll check in on their tiles and take photos, and over the months the photos should play like a flip book in showing the growth of the oysters on each site. They’ll gain understanding, and they’ll run into more road blocks. They have about two-and-a-half years left on this study, so while Thursday was the last day of the push, they’re nowhere near the end of the road.
Assuming no one tampers with them, we should be able to watch these oysters grow up over the next year.
Check back in a couple of weeks for wrap-up posts from David and Tanya.
Tide Times and height (ft.) for Jacksonville, October 28, 2010
Low- 6:44 AM (0.3)
David’s research is funded by the National Science Foundation.
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I went to graduate school in northern California. Locals along the coast of NorCal used to refer to the month of October as Roctober because it was the most beautiful time of the year. Well, I think the Forgotten Coast should also be privy to this monthly description because things have been beautiful around here this month. Looking at the oyster reefs, I get the sense that things are really starting to get busy in there. But I wonder if the ecology on oyster reefs in NC is starting to slow down. Where are predators really having a big effect? We shall soon see.
For the past week, we have been trying to figure out how to do a lot of ambitious seeing and learning on all of our reefs. All three teams (i.e., NC, SC/GA, and FL) need to not only sample fish and invertebrate predators on reefs (for the second time and in the dark…all because of the timing of tides in the autumn), but each team also needs to simultaneously squeeze in an experiment. Oh, I just remembered that we also need to pay attention to other things that can explain oyster patterns: oyster food in the water (phytoplankton), water temperature, tides, and sediment properties. So, add those to our to-do list as well!
Because this will be a ton of work to do in a short amount of time, we are sending a new crew member of the Florida team (Alicia Brown) up to help out the South Carolina/GA team. We are going to send her up with a video camera, so it will be fun to get a glimpse into their lives over the next week.
Jon Grabowski holds up a fish for Tanya to measure. David was Jon's lab tech at UNC.
In addition, one of the leaders from North Carolina (Jon Grabowski) has been down with us in Florida for the past week to help make sure that all three teams are doing the same thing. While he was here, we also worked with a wonderful assistant up in Georgia (Caitlin Yeager) to figure out how to manufacture our experimental products. The first part of this experimental puzzle involved figuring out how to remove baby oysters (spat) from oyster clumps in the field and to attach them to a standardized surface (tile). Across all of our sites, we all want to start out with oysters of roughly the same size and age; otherwise, differences in our experiments among sites could simply be due to differences in starting oyster size or density, rather than to differences in predator diversity etc. After we get all the spat attached to our tiles, we then built (well Tanya built most of them- thanks Tanya!) structures to put around our tiles, or not…
A partially open cage (cage control) that lets predators eat the oyster spat.
Our first structure was built to exclude all predators from munching on our oysters (i.e., predator cage). Our second structure was a modified exclosure that mimics physical characteristics of the exclosure, but still allows predators to munch oysters (cage-control). Finally, we have naked tiles that receive no structure or cage. At 2 sites in NC, 2 in Georgia, and 3 in Florida), we will put each of these ‘treatments’ on all of the reefs (15 tiles/estuary or 105 tiles total).
But why do this crazy experiment thing? Well, we will come back each month and monitor the traits of oysters and their survivorship. With these results, we will compare survivorship or oyster traits from cages to that of the naked tile (“control”) to see if excluding predators improved oyster survivorship. But because any improvement of oyster survivorship by the cage could simply be due to the physical structure (not to predator absence) providing shade during low tide or somehow changing flow (and food delivery), we will then compare cage results to that of the cage-control; now we can tell just how important predators are.
Another cool thing about the cages is that it may exclude predators from eating oysters, but they will not prevent predators from affecting traits of the oysters through intimidation. So, do the traits of oysters surrounded by cages in Florida (maybe more oyster consumers) differ when compared to caged oysters in NC (maybe fewer oyster consumers). Or, perhaps it’s that FL has more oyster food this time of year than NC and that better explains trait differences in oysters, not predators. Or, maybe larger fish predators in Florida means less oyster consumers and less influence of oyster predation in Florida compared to NC, where there may be fewer large fish predators to eat the smaller crabs that love to munch on oysters.
To pull off this extra work, my Florida team will divide and conquer over the next week and a half. Out of a team of four, 2 people will trap and gill net while the other two folks will set up the experiment. This will involve ½ the team moving a head of the other team members at certain points. But we’ll all overlap at each site for at least a few hours, which will then result in interesting stories about what each team has been observing. Because we want to share this circus show with you over the next week, we’ll post updates every day. We hope that this gives you a feel of what it’s like to get all of this done (both the good and the bad!).
Well, I need to go stockpile some sleep.
David’s research is funded by the National Science Foundation.
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.