Tag Archives: coastal ecology

In the Grass, On the Reef, A World Away

Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip- biogeographic 150IGOR chip- habitat 150David and I are in Sydney, Australia, on visiting research appointments with the University of Technology Sydney. We arrived the first of the year, and after recovering from jet lag and getting our bearings, we embarked this week on setting up a couple of new experiments.  We have great local “guides” – Dr. Peter Macreadie (UTS), Dr. Paul York (UTS), Dr. Paul Gribben (UTS), and Dr. Melanie Bishop (Macquarie University) – to introduce us to the field systems and collaborate with us on these projects.

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Our seagrass and razor clam experiment is set up at Point Wolstoncroft in Lake Macquarie (north of Sydney).

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Photo feature: Oyster Love

From the FSU Coastal & Marine Lab

IGOR chip- human appreciation 150What’s not to love about oysters? They clean the water, they’re delicious, and they have surprising economic value. Members of the Kimbro Lab found this unique oyster, which itself seems very loving, on one of their study sites. “Now I’ve seen a lot of weird-shaped oysters,” says lab tech Tanya Rogers,” but never one quite this perfect. I took it on a photoshoot this evening for some nice background and lighting.”

A long time in the making

Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip- biodiversity 150

As I mentioned in my last update, we have been working to set up a new marsh experiment in St. Joe Bay. The goal of the experiment is to see whether the genetic diversity of marsh cordgrass (Spartina alterniflora) affects how quickly or abundantly the plants grow, or influences the number of fiddler crabs, grasshoppers, snails, and other critters (like Ibis??) that call the plants home. But what is genetic diversity, exactly, and why do we think it may be important?

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A flock of Ibis resting among our experimental marsh plots.

Spartina is a clonal plant, which means that a single “individual” or clone made up of many stems can dominate a large area (low diversity), or there can be lots of different individuals mixed together (high diversity). In our surveys of marshes in the northern Gulf of Mexico, we find that there can be as few as 1 and as many as 10 clones in an area of marsh about the size of a hula-hoop. You may notice that our experimental plots are about that same size, though we used irrigation tubing rather than actual hula-hoops (not as fun, but more practical and less expensive!). We’re testing whether the differences in genetic diversity (1 vs. 10 clones) that we see in natural marshes has any influence on the marsh community.

A single experimental plot of Spartina that is 1m in diameter.

But why genetic diversity? We know from experiments by other researchers that Spartina clones grown individually differ in height, how many stems they have, and other characteristics. These same plant traits affect the critters that live in and among the plants – for example, periwinkle snails preferentially climb on the tallest plants. Because different animals may be looking for different plant traits, then having greater diversity (genetic and trait) may lead to a greater number of animal species that live in that patch of marsh. Or, a single clone may be the “best”, leading to higher numbers of animals in lower diversity areas.

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A view of the existing marsh behind our experiment.

As my title alludes, this experiment has taken a long time to come to fruition, in large part because it’s impossible to look at any 2 stems in a marsh and know for certain whether they’re the same individual or not. Unlike some clonal plants such as strawberries, where there are multiple berries connected by a single above-ground “runner”, Spartina has runners (aka, rhizomes) that connect stems of the same genetic individual under the ground, making it difficult to tell which stems are connected to which. We have 2 ways to get around this problem: (1) we use small snippets of DNA (analyzed in the lab) to tell clones apart, and (2) we start with single stems that we know are different clones and then grow them separately in the greenhouse until we have lots of stems of each different clone. It’s this latter part that has delayed this experiment – it has taken much tender loving care from Robyn over the last 2 years to get our Spartina clones to grow in the greenhouse to the point that we have enough of each clone (36 small flowerpots of each, to be exact) to plant in our experiment.

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Emily and Robyn work to remove existing rhizome material from around the plot edges.

But plant we finally did! With lots of help from members of the Hughes and Kimbro labs, we got all the sand in the experimental plots sieved (to remove any existing root material) and all the plants in the ground the Thursday and Friday before Thanksgiving.

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Team Hug-bro (Hughes and Kimbro) helping sieve sand!

 

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Meagan and Randall get the easy job - planting the plants.

Now we get to wait and see (and take data) whether Spartina genetic diversity matters for the marsh plant or animal community. There won’t be any quick answers – the experiment will run for at least 2 years – but we’ll be sure to keep you up-to-date!

Randall’s research is funded by the National Science Foundation.

Switching gears: from kayak to office cubicle

Hanna Garland FSU Coastal & Marine Lab

IGOR chip_ predators_NCE 150As fast as summer approached, it is now over; and for myself, it marks the closing of an intense field season and the beginning of my first year as a graduate student. However, this does not mean that the experiments, laboratory work, and data collection is put on hold. There is still plenty of work to check off the “to do” list that seems to never get any shorter.

My last post introduced the scientific question I was hoping to answer and the reason for studying the relationship between crown conchs and oysters in the Matanzas River as opposed to a different location. While I did not answer the question entirely (that would be far too difficult to accomplish in one summer), I was able to establish a strong, preliminary data set that I can now analyze and re-configure in order to improve upon this research next season.

Similar to methods described in David and Tanya’s posts, the construction of my experiment consisted of (much smaller) trenches dug for cage installation, Z-spar for attaching oyster spat to tiles, bumblebee bee tagging kits for marking appropriately weighed and measured oyster clusters, and various amounts of PVC for expensive data logger equipment housing. The fun meter never stopped ticking this summer in St. Augustine!

As I sit in my cubicle in my new office on campus, my mind cannot help but wander back to my life this summer driven by the time of low tide and whether I would have enough sunlight or energy to kayak out to one more site. To my surprise, the running of my experiment was manageable and actually became a relaxing routine. Data collection was divided into three categories: conch surveys, oyster health, and data logger maintenance. The number of conchs found on the experimental reefs was recorded in order to quantify the varying densities of these predators at each site. The health of the small oysters attached to tiles as well as the tagged larger clusters were assessed based on the number of live and dead. The data logging instruments record the water temperature, salinity and amount of tidal inundation occurring at each of my six experimental oyster reefs every five minutes (so there are a lot of data points to be analyzed here!) and require periodic scrubbing to remove algal and barnacle growth.

While the daily workload may seem light as far as stress levels; the fine print of every step of an experiment can be a tremendous mix of emotions. The hope for not just data but “good” data is something that all scientists share; however, this does not mean that conducting research needs to be filled with anxiety. The outlook that I aimed to have this summer was more based on the feelings of excitement and opportunity rather than high expectations that may or may not be met. To be able to conduct this study in such an ecologically rich environment surrounded by intelligent, supportive, and proactive people and institutions is an accomplishment in itself.

While my data set still requires endless hours of manipulation and analysis, the general outcome of my experiment this summer revealed that there is in fact an oyster health gradient occurring along the Matanzas River, with a change in health occurring around the Matanzas Inlet. In tandem with this increasing oyster mortality moving from my sites north of the inlet to the sites south; are high densities of crown conch populations on the southern reefs, with a decrease in these populations moving towards reefs north of the inlet. Furthermore, environmental factors (water temperature, salinity and tidal inundation data collected by my instruments) will be considered when looking at these patterns.

As a way to better quantify the health and size of the oyster community as well as the density of the resident species (such as crabs, worms, and other amphipods) that inhabit oyster reefs; I surveyed and sampled background reefs at each of my six experimental sites. Long story short, this meant that I randomly selected four new oyster reefs at each site in which I collected environmental data and basic reef characteristics (type of reef, location, dimensions), conducted conch surveys, and collected every living oyster cluster, dead shell, crab, piece of biota, etc. inside of a 0.25 x 0.25 meter quadrat. After washing away the mud, extracting the living organisms and preserving them in ethanol, and weighing, measuring, and recording each live and dead oyster, I have developed a solid database of the oyster reef communities at each of my sites. This will help to better describe the type and abundance of species present at each site.

Oyster reef communities impact us in more ways than providing a tasty appetizer at a restaurant. Not only do they provide a habitat for commercially and ecologically important species, but they also serve to locally improve water quality and prevent erosion. Oyster reefs are complex communities that are in a state of decline along the Florida coast. Unfortunately, unhealthy oysters cause unhealthy or collapsed resident species communities because these organisms depend on oyster reef habitats for food, shelter, and other important aspects of their life cycle. This experiment and preliminary data set provides insight to changing food web dynamics occurring not only along the Matanzas River but in all oyster reef communities.

Apalachicola oysters

Tasty as they are, oysters have a far greater ecological- and economical- value when they're alive in their oyster reefs.

Whether you are enjoying seafood for dinner or driving on a bridge over estuarine environments, keep in mind the important role each individual species plays in a larger community structure. Our actions upstream of these fragile habitats impact everything from microscopic worms to the maturing oyster spat and larger fish populations. As my project evolves, I hope to not only strengthen the scientific community but also raise awareness among people who unknowingly influence an aspect of oyster reef habitats.

 

Are two friends better than one?

Dr. Randall Hughes FSU Coastal & Marine Lab

IGOR chip- biodiversity 150

Sand fiddler crab.

This summer we’ve been conducting an experiment on our new deck to look at the effects of fiddler crabs and ribbed mussels on Spartina alterniflora (smooth cordgrass).

Past studies by Dr. Mark Bertness have shown that crabs and mussels by themselves can have positive effects on plant growth – most likely because crabs can reduce the stress of low oxygen in the sediments by building their burrows, and mussels can add nutrients to the sediments.

Fig. 3 from Bertness 1984, Ecology 65: 1794-1807

Figure 3 from Mark Bertness's 1984 Ecology study illustrating the positive effects of mussel presence (white bars) on Spartina

Table 3 from Bertness 1985, Ecology 66: 1042-1055

Table 3 from Mark Bertness's 1985 Ecology study. Fiddler removal has a negative effect on Spartina in the marsh flat, but not the marsh edge.

Although both fiddlers and mussels occur together in the field, no studies have looked at how the combination affects the plants. Are the positive effects of each species by itself doubled? Or are they redundant with each other? Do crabs somehow reduce the positive effect of mussels, or vice-versa? How many crabs or mussels do you need to get a positive effect on Spartina? These are some of the questions that we hope to answer with our experiment.

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Our new deck at FSUCML.

But first, we had to get everything set up. There were several long and hot days of shoveling sand into our “mesocosms” (10 gallon buckets) – many thanks to Robyn, Chris, Althea, and all the others who took care of that task! Then there was another day spent transplanting the Spartina.

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Chris, Randall, and Robyn work to transplant Spartina from the greenhouse to the mesocosms.

Finally, it was time to add the fiddlers and mussels, and everything began!

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Mussels nestled among the Spartina stems in one of our experimental mesocosms

Althea and Chris have been leading the charge on this experiment, and they’ve spent a lot of time getting to know (and identify) the fiddler crabs. All in all, a pretty fun study organism!

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Althea working to identify fiddler crab species.

We’ll continue the experiment another month and then measure the height and density of the plants in each treatment to see if there are any differences. Once this experiment is complete, we’ll set up a separate one asking somewhat of the converse question – are two enemies (periwinkle snails and grasshoppers) worse than one? We’ll keep you posted.

Randall’s research is funded by the National Science Foundation.
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