Monthly Archives: July 2013

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The Many Personalities of Salt Marsh Cordgrass

2-Minute Video: Do sea turtles and fishermen benefit from a genetic diversity in marsh cordgrass?

As Randall mentioned in her last post, biodiversity can mean many things. In this video, she examines diversity within a species, in particular marsh cordgrass (Spartina alterniflora). Each Spartina plant has its own personality. What Randall wants to know is: are more personalities better for a salt marsh (and the sea turtles and blue crabs that use it)?
Dr. Randall Hughes FSU Coastal & Marine Lab / Northeastern University

Its difficult to see the diversity of the cordgrass in this vast sea of green.IGOR chip- biodiversity 150One of the more striking things about a salt marsh at first glance is how uniform it is. A sea of green. Or maybe a sea of green (cordgrass) in the intertidal and brown (needlerush) further back. But definitely not something that screams “diversity”.  And yet, wondering about the importance of diversity in the salt marsh is what I spend a lot of my time doing.

Often, when scientists talk about diversity, they are referring to different species of plants and animals (= species diversity). But there are actually lots of different kinds of diversity – functional diversity, phylogenetic diversity, genetic diversity. To illustrate what these terms mean, let’s shift to the topic I most like to think about when I’m not thinking about science – FOOD. Functional diversity is one of the broader categories, where different species are grouped by how they look or behave. So, think vegetables vs. fruits. Or, even green leafy veggies vs. root vegetables vs. berries vs. melons. Phylogenetic diversity refers to how related the species are – broccoli and cauliflower are more closely related (and thus have less phylogenetic diversity) than broccoli and zucchini – whereas species diversity refers to how many different species there are. Finally, even a single species can have a lot of diversity within it – apples are a perfect example of a fruit with large numbers of varieties to choose from. It’s this last level of diversity, genetic diversity, that I’m really interested in.

Some of a Spartina plant's below ground root structure.  Many of the plants used in Randall's experiment have sent out rhizomes under the sediment which have sprouted new shoots.  If you're at the edge of a salt marsh and see a line of marsh cordgrass plants sticking out into the water, they're likely connected by such a rhizome.

Some of a Spartina plant’s below ground root structure.  Many of the plants used in Randall’s experiment have sent out rhizomes under the sediment which have sprouted new shoots.  If you’re at the edge of a salt marsh and see a line of marsh cordgrass plants sticking out into the water, they’re likely connected by such a rhizome.

Unfortunately, it’s not as easy to tell different ‘varieties’ (aka, genotypes) of cordgrass apart as it is to tell a Granny Smith from a Red Delicious. Most of the plants look really similar, and it’s impossible to tell by looking from above the ground which ones are connected by roots and rhizomes below the ground. I have 2 solutions to this problem:

1. Take small pieces of cordgrass into the lab and use even smaller snippets of DNA to tell who is who. (As my dad says, think CSI with grass.)

2. Take a single cordgrass stem and grow it in a flowerpot in the greenhouse until it starts to produce lots of other stems. By splitting these up and allowing them to continue to grow (and keeping careful track of which pot is which), I can produce a supply of known cordgrass genotypes to do experiments with.

Neither of these techniques happens overnight. In fact, it took us nearly 2 full years to get enough genotypes in the greenhouse to start doing experiments with! (Proof that even someone without a green thumb – like me – can work with plants, but it takes longer than it should.)

Each bar in these graphs represents a different marsh cordgrass genotype. You can see how each plant differs in "personality" from its number of stems and flexibility.

Each bar in these graphs represents a different marsh cordgrass genotype. You can see how each plant differs in “personality” from its number of stems and flexibility.

The cool thing about spending that much time with these plants is that you start to recognize that they have their own flavors or personalities. Some grow a few really tall stems vs. others with lots of average size stems; some flower in July vs. others that flower in October; some have really flexible stems vs. others that are more rigid (which probably matters if you’re a snail climbing up the stem).

It’s these different personalities that may allow a mixture of multiple genotypes to do better over time than a genotype growing by itself. For one, if some genotypes are better at surviving some sort of disturbance, then having a mixture of genotypes increases the chances that one of those “good” genotypes is included in the mix. Or, if genotypes are all a little bit different, they may be complementary to one another, allowing the mixture to do better than any one of them growing alone. (This “complementarity” can also be referred to as facilitation, and it’s an idea we’ll return to in coming weeks.)

We have several experiments that are wrapping up now that test this very idea – do diverse marsh patches perform better than less diverse patches? If so, why does that happen? Early indications are that the answer is like a lot of things in nature – it depends. Sometimes the diverse patches do better, and sometimes they don’t. So now the trick is to figure out how to predict when diversity will matter, and use that information to help conserve existing salt marshes and restore marshes that have been damaged in the past (which can help provide a steady supply of blue crabs for both sea turtles and us!).

Music in the piece by airtone.  Thanks to Mineral Springs Seafood for letting us tag along as they emptied their crab traps.  And thanks to Gulf Specimen Marine Lab for the underwater footage of Allie the sea turtle (good luck out there, Allie!).

This material is based upon work supported by the National Science Foundation under Grant Number 1161194.  Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

GIC

Grasses in Classes: Kids Learn to Build a Salt Marsh

Rob Diaz de Villegas WFSU-TV

Last week, we took a good look at the coastal salt marsh- an ecosystem with a lot to offer but that is seeing die-off across the world. Around Choctawhatchee Bay, schoolchildren are doing something about this.

Two “spoonbills” fight for lima bean. Students at the Laurel Hill School did more than plant marsh cordgrass on the coast. At this station, they were given three types of tools to use as beaks: clothespins, spoons, and chopsticks. With those beaks, the “birds” had to forage for food. The exercise taught them about the adaptations that give animals different advantages. The best adapted beaks got the most food.

IGOR chip- sedimentation 150

Finding out about Grasses in Classes was one of the pleasant surprises of the year so far.  The Choctawhatchee Basin Alliance and AmeriCorps start with a similar premise to the In the Grass, On the Reef project: to foster appreciation for coastal ecosystems like oyster reefs, seagrass beds, and salt marshes.  We write and make videos for a general audience; Grasses in Classes goes into schools.  What they do goes beyond lesson plans and worksheets.  These kids grow smooth cordgrass (Spartina alterniflora), the foundation species of a coastal salt marsh, in their classrooms.  Then they go to Choctawhatchee Bay and plant it.  How awesome is that!  You can see in the video how much the cordgrass spreads out over the course of the year, a powerful visual affirmation to the Laurel Hill School students that what they’re doing is having an impact and will benefit that coastline for years to come.

A few yards from their marshes are restored oyster reefs like the ones CBA builds in the bay.  They’re frequent collaborators, the salt marsh and oyster reef.  Marshes, oyster reefs, and seagrass beds join to create an estuary of critical importance to Gulf fisheries, sheltering most seafood species fished there at some point in their life cycles. As was said in both this and the O.Y.S.T.E.R. Recycling video, marshes and oyster reefs fight erosion.  Marshes also filter stormwater runoff (check this list of everything that flows off of asphalt).  And yet, probably because no amount of horseradish makes Spartina grass palatable, marshes don’t always capture the popular imagination as oyster reefs do.  I hope we can change some of that in the coming weeks.

That’s where the CBA might have us beat.  Through their work, a generation of schoolchildren is getting that appreciation the wet and dirty way, by actively restoring that habitat where development had removed it.  And with the school year recently concluded, CBA and AmeriCorps are gearing up for next year by hiring 13 full time employees to continue to carry the program out.  Click here for more information.

Kayla Mitchell helps a Laurel Hill student plant a Spartina plant.  Spartina is the foundation species of a coastal salt marsh.

Kayla Mitchell helps a Laurel Hill student plant a Spartina plant.