Tag Archives: Alligator Harbor

Roctober!

Dr. David Kimbro FSU Coastal & Marine Lab

IGOR chip- biogeographic 150I 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.

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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…

Tile Experiment

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.

See ya,

David

David’s research is funded by the National Science Foundation.
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Days 1 & 2: October Oyster Push- “Just Gun it”

Rob Diaz de Villegas WFSU-TV
Alligator Harbor at sunrise

The sun is about to rise in Alligator Harbor.

IGOR chip- biogeographic 150The first leg of David Kimbro’s Roctober oyster push is now complete.  If you look at the schedule below, you’ll see the first day was intensive, starting in the wee hours and going late into the night.  As David mentioned in his post, the head of the NC team (Jon Grabowski) was along for the fun.  David was Jon’s lab tech once upon a time, as was Dr. Randall Hughes (In the Grass).  So tagging along I definitely got some “family reunion” vibes, with lots of good natured ribbing (let’s just say it was good-natured).

For this October push, David will be breaking in a new boat to help his team cover ground more efficiently while lugging traps and samples around.  In order for the boat to move in shallow water, David replaced the motor with a lawnmower engine.  It worked fine on Thursday, when the water was higher, but it had a few problems Friday morning at low tide:

Jon drags the boat- and Tanya and Alicia

Jon Grabowski drags the boat- along with and Tanya and Alicia- after not being able to drive the boat through shallow waters.

Finally, they were able to get it to go.  The solution?  As David’s tech, Hanna, said- “Just Gun it!”

The catch this time was a little different than the last, with new fish like Red Drum ending up in the gill nets and no juvenile fish being caught in the minnow traps.  They also started looking into the stomachs of some of the predators (they have a permit to do so if the fish die in the net) and are seeing that the catfish here are eating mud crabs.  Mud crabs, of course, are key oyster predators.

Hanna kayaks

Early Friday morning, Hanna Garland kayaks to "site 1" in Alligator Harbor.

We’ll be heading out with David’s crew throughout the week.  On top of all of the other arrangements they have to make to move their crews around multiple sites hundreds of miles apart, they have to accommodate our camera crew.  So thanks for finding a way to drag us along!  Hopefully we can show people the kind of work that goes into making this kind of research happen.  There’s a lot of work to go along with the science, and with every subsequent sweep and new experiment, the patterns will hopefully clarify and our understanding of these ecosystems- and how to best conserve them- will be that much further advanced.

David’s crew has been split into two teams, the Net/Trap team (N/T) and the Tile team (TI).  For a closer look at how David’s team nets and traps larger fish and crabs, click here.  To learn more about what the Tile team will be doing, click here.  And if you click On the Reef under categories in the sidebar, you can track David’s progress over the course of this study.

Thursday, October 21-  Alligator Harbor

8:30 AM- Retrieve tiles, sediment, and spat. (TI)

11:07 AM- Deploy traps (N/T)

5:07 PM- Retrieve traps.  High tide activities: reference water level, water samples, replace spat sticks.  Unlike in the previous sampling done in Alligator Harbor, there were no juvenile pinfish or pigfish.(N/T)

8:00 PM- Deploy nets.  The nets will be retrieved Friday morning to give David an idea about what was swimming around over night.  (N/T)

Tide Times and height (ft.) for Alligator Harbor, October 21, 2010
Low-  8:07 AM (0.2)
High- 2:12 PM (2.7)
Low- 8:07 PM (0.9)

P1010300Friday, October 22-  Alligator Harbor

8:00 AM- Retrieve nets, data logger.  Today there were a lot of red drum (redfish) and of course, catfish (hardhead and sail).  On site dissection reveals that the catfish eat mud crabs, thus serving the same role that toadfish serve in North Carolina reefs. (N/T)

8:30 AM- Return tiles/ oysters.  The tiles for the new spat experiment mentioned by David go out today. (TI)

Tide Times and height (ft.) for Alligator Harbor, October 21, 2010
Low-  8:40 AM (0.1)

David and his team are taking Saturday off.  Bright and early Sunday morning, the Net/ Trap team heads for Cedar Key while the Tile team heads to Saint Augustine.

David’s research is funded by the National Science Foundation.
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Why do we eat Apalachicola oysters instead of those from Alligator Harbor?

Dr. David Kimbro FSU Coastal & Marine Lab

IGOR chip- gastronomy 150IGOR chip- biogeographic 150In my previous post, I described how tides could influence the oyster patterns that we are observing throughout the Atlantic and Gulf coast.  But throughout the Gulf coast, can tides explain why most of the oysters sold in restaurants come from subtidal reefs?  Are subtidal oysters healthier, happier and thus more abundant?

Well, before I attempt to address this issue, let’s first talk about the difference between subtidal and intertidal oyster reefs.  The term intertidal refers to a habitat that spends part of the day submerged by water and the other part of the day out of the water.  In contrast, the term subtidal refers to habitats that are constantly submerged by water.  Interestingly, along the NW coast of Florida, oyster reefs are subtidal from Pensacola to Apalachicola Bay.  And east of Apalachicola, oyster reefs become intertidal.

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Fouling organisms grow on hard surfaces under water.

Now back to the second question above: are subtidal oysters happier and healthier than intertidal oysters?  Research by Dr. Charles Peterson at the University of North Carolina at Chapel Hill suggests the answer is no because both reef types have different costs and benefits that keep growth and health roughly the same.  For example, subtidal reefs may get the benefits of being inundated all the time by food-rich water, but this constant submergence also has costs that include: getting covered by fouling invertebrates (i.e., animals commonly found on the bottom of boats that look like silly puddy) that compete with oyster for food and being exposed to more marine parasites and disease.  In contrast, the harsh sun baking that intertidal oysters receive during every low tide can be painful and they may also get exposed to less food, but the sun baking also cooks off the silly-puddy competitors and it also keeps the parasites away.  In the end, these different costs keep growth rates about the same between subtidal and intertidal oyster reefs.  This is why intertidal oysters from Cedar Key, Florida can be just as big and delicious as subtidal oysters from Apalachicola.

Now I’m ready to tackle the first question  from above: why do so many more oysters come from subtidal reefs in Apalachicola than from the intertidal reefs to the east and why aren’t intertidal oysters always equally as large and tasty as subtidal oysters?  After talking with an extremely knowledgeable biologist who has been studying and working with Gulf coast oysters for nearly thirty years (John Gunter), I can fairly confidently say that the answer deals with the size of the fresh water input entering an estuary and diversity.  This is because good oyster production requires a tricky balance between fresh and salty water that keeps marine predators/disease at bay and fuels phytoplankton for growth and reproduction.  So, a larger source of fresh water input creates a larger portion of an estuary suitable for oysters to achieve this delicate balance.  But the amount and timing of fresh water input, along with the weather, varies from year to year.  As a result, one set of fresh-water input and weather conditions may be good for one portion of the estuary and not so good for the other portion of the estuary.  But the next year, this situation could become reversed, maintaining a constant level of production through varying levels of fresh water input and climate.  In other words, Apalachicola has a relatively large and diverse oyster portfolio.

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Without a steady influx of freshwater, intertidal reefs have no assurance of being consistently healthy and abundant.

In contrast to the subtidal oyster reefs in Apalachicola, the size of fresh water sources that influence intertidal oyster reefs to the east are significantly smaller.  Consequently, there are only a few spots where oysters can thrive.  When conditions are just right, these intertidal reefs produce oysters just as tasty and large as the subtidal ones form Apalachicola.   But when conditions are sub-par, those intertidal oyster reefs shut down and there are no other reefs to make up for this loss in production; these estuaries have small and non-diverse oyster portfolios.

Ok, now that I waved my arms about the difference between subtidal and intertidal oyster reefs and why restaurants mostly serve subtidal oysters, I need to go get ready for our next big outing onto the oyster reefs, which should be extremely busy, but fun.

Talk soon,
David

David’s research is funded by the National Science Foundation.
We want to hear from you! Add your question or comment below.

Searching for alternative explanations

Dr. David Kimbro FSU Coastal & Marine Lab

IGOR chip- biogeographic 150In 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

This is what an oyster reef looks like…

Rob Diaz de Villegas WFSU-TV

IMG_3499

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.

Continue reading