Ecology

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The Crab Tow Tango

Monday, July 29th, 2013

by Katie Sinclair

Brooke and Paige get ready to deploy the tow.

Brooke and Paige prepare to deploy the tow.

There is a certain art to the deployment of a crab tow. This brown metal and net contraption, about three feet long and a foot wide, scrapes over the bottom in search of juvenile blue crabs. Fitting three people, two coolers, a selection of buckets and bins and the tow in a 16-foot jon boat is something akin to a giant game of Tetris. Successfully launching and recovering the crab tow without smacking anyone in the face or knocking anything overboard requires practiced choreography and grace.

With a one-two-three, the metal tow hits the water with a splash. After 300 feet, lab tech Paige Roberts gracefully maneuvers the jon boat backwards and forwards to retrieve the tow. Paige captains the jon boat a bit like a fighter pilot—precision is required to coax the unwieldy boat around shoals, patches of sea grass and oblivious jetskiers. Click to continue »

Hunt for a Missing Nutrient: Part II

Wednesday, July 24th, 2013

By Katie Sinclair

Alyssa and Carey begin their search for key nutrients in a stream in the Choptank Watershed.

Alyssa and Carey begin their search for key nutrients in a stream in the Choptank Watershed.

The nutrient lab is still plagued by the mystery of the missing nitrogen. More nitrogen enters the watershed than exits it, and the question remains: Why?

How much nitrogen makes it to the bay can have huge impacts on the water quality and bay health. The Choptank watershed, in a farm-heavy area, has much lower levels of nitrogen in stream water than expected. As farmers add fertilizer to their crops, some nitrogen gets taken up by the plants, and the rest washes away into the watershed , eventually reaching the Chesapeake Bay. Of the nitrogen that is added as fertilizer, only 20 to 30 percent of it is accounted for.

In a narrow, slow-moving stream in the Choptank watershed, fondly nicknamed “Pizza Branch” (due to its proximity to a lone pizza joint puzzlingly located in this predominantly farming area), researchers working under Tom Jordan, Principal investigator of the nutrient lab at SERC, are using different methods to help determine what’s happening to the nitrogen. The project is a joint effort between SERC and Tom Fisher’s lab at the Horn Point Laboratory of the University of Maryland.

Researchers brave high heat, humidity, and voracious mosquitoes to take water samples, a process that can take all day. While taking water from a stream may seem like a straightforward undertaking, the true complexity comes through in the lab, where analysis of microscopic dissolved compounds can reveal the secrets of a watershed.

“It’s a fun challenge to go all over a stream and take samples and bring them back to the lab, to discover things you can’t see with your eyes,” said Jordan.
Click to continue »

From the Field: Out of the Mangrove and into the Marsh

Monday, July 22nd, 2013

by Megan Riley

University of South Carolina Ph.D. student; Smithsonian Marine Station visiting scientist

Mangrove tree crabs crowd onto a dwarf red mangrove, in a hybrid mangrove-marsh region. (Megan Riley)

Mangrove tree crabs crowd onto a dwarf red mangrove, in a hybrid mangrove-marsh region. (Megan Riley)

Home for most species largely depends on climate: temperature, light and rainfall. With changes in global climate trends, many plants and animals are expanding their geographic limits poleward. However, not all species in a community respond to these changes in the same way.

Organisms often differ in the type and timing of their responses to environmental changes. Sometimes, animals expand more quickly than the habitats they’re used to. When this happens, these organisms are forced to colonize unfamiliar habitats where they often face numerous challenges, like resource shortages and never-before-seen predators.

So how do these animals alter their behavior, resource use and reproductive strategy to succeed in their new habitats? I aim to explore just that question by studying the range expansion of the mangrove tree crab Aratus pisonii into salt marsh habitats.

Mangrove tree crab Aratus pisonii on a black mangrove tree. (Megan Riley)

Mangrove tree crab Aratus pisonii on a black mangrove tree. (Megan Riley)

Mangrove tree crabs are native to Florida and abundant throughout Floridian mangroves, where they are the dominant herbivores of fresh mangrove leaves. Like mangrove trees, they have slowly begun moving northward. But the crabs are moving faster than the mangroves—and they’ve begun to invade salt marsh territory. They can be found crowding onto isolated dwarf mangroves nestled amidst cord grass, as well as in salt marshes with no mangroves in sight!

How mangroves are taking over marshes

Because mangrove tree crabs in their native habitats rely heavily on mangroves for food and shelter, their habitat shift into salt marshes also causes a diet shift that can impact their growth, survival and reproduction. By focusing on the range expansion of mangrove tree crabs into salt marshes during my time at the Smithsonian Marine Station this summer, I hope to shed light on what exactly is enabling this species and countless others to successfully expand their range into new environments.

High CO2 Spurs Wetlands to Absorb More Carbon

Tuesday, July 16th, 2013

by Kristen Minogue

"Marsh of the Future." Bert Drake built these chambers in 1987. Inside half of them, he raised CO2 to roughly 700 parts per million, a level we could reach before the end of the century. (SERC)

“Marsh of the Future.” Bert Drake built these chambers in 1987. Inside half of them, he raised CO2 to roughly 700 parts per million, a level we could reach before the end of the century. (Tom Mozdzer/SERC)

Under spiked carbon dioxide levels, wetland plants can absorb up to 32 percent more carbon than they do today, according to a 19-year study published in Global Change Biology from the Smithsonian Environmental Research Center. With atmospheric carbon dioxide passing 400 parts per million in May, there’s hope that wetlands could help soften the blow of climate change.

But that isn’t the shocking part for plant physiologist Bert Drake. The shocking part is that plants are absorbing the carbon in ways they didn’t expect.

Click to continue »

What’s eating the tropics?

Tuesday, July 16th, 2013

by Kristen Minogue

A mangrove tree crab eats a beetle larva. (Candy Feller / Smithsonian Environmental Research Center)

A mangrove tree crab eats a beetle larva. (Candy Feller / Smithsonian Environmental Research Center)

As a general rule, the tropics have more of everything—more plants, more animals and more microbes. This also means they have more predators. For their prey, this is usually a bad thing. But for the rest of the ecosystem, a diverse army of predators can have some surprising perks.

It’s happening in the mangrove forests of Panama and Belize. With the vast array of plant-eaters in the canopy, biologists once thought the tropics would be a danger zone for mangroves. But SERC ecologist Candy Feller discovered something unexpected. After tracking mangroves in Panama, Belize and Florida in a study published this June, her team found that mangroves were actually safer from hungry herbivores in the tropics.

It turns out one species threatens mangroves more than any other: the mangrove tree crab, Aratus pisonii. And in the steamy Central American forests, something else seems to be eating them.

Click to continue »

From the Field: Oysters from Chincoteague

Tuesday, July 16th, 2013

by Katrina Lohan, Smithsonian postdoc

Kristy Hill and Michelle Repetto hunt for oysters on an exposed marsh in Chincoteague Bay. (Katrina Lohan)

Kristy Hill and Michele Repetto hunt for oysters on an exposed marsh in Chincoteague Bay. (Katrina Lohan)

For our final sampling site, we headed north to Chincoteague Bay. Edward Smith, our boat captain, had made sure to find a location that wasn’t currently leased to a local fisherman. He was confident we would find oysters, but he wasn’t sure about mussels or clams.

For some additional manpower, three summer interns from the Eastern Shore Laboratory accompanied us. Our sampling location was adjacent to Wallops Island, a NASA facility. We got to work as soon as Edward stopped the boat. Edward and the interns started raking for clams, while the rest of us grabbed oysters and mussels from the exposed marsh.

The mud here was also thick and deep! Once we had all the oysters and mussels necessary, Kristy and Michele aided in the search for clams while I recorded all the necessary metadata and took sediment and water samples. When the tide started to come in we had to halt our sampling efforts. Though we didn’t find as many clams as we wanted, we had enough to make processing them worthwhile. It was a great time for our final collecting trip of the season!

View full series on hunting for oyster parasites >>

From the Field: Accident in a Storm Surge

Friday, July 12th, 2013

by Katrina Lohan, Smithsonian postdoc

On Friday, we jumped in the boat for a quick ride to a nearby oyster reef just outside the inlet at Wachapreague. Unfortunately for us there was a storm surge of a few feet, so the area that should have been completely exposed at low tide was still mostly underwater. Our boat captain, Edward Smith, took one look around and told us to hurry, as we probably only had one hour to collect all the bivalves we needed.

Edward and two summer interns started to rake for clams, while Michele, Kristy and I headed for oysters and mussels. It was slow going as the water was mucky and the mud was thick. It was a bit of a leg workout!

I collected at one site and then moved on to the next when I heard Michele yell for me that she had cut her leg on an oyster and needed to head back to the boat. She left her collecting bags so Kristy knew where she had been, and she and Kristy switched out at that location. After I had gotten all I needed, I got back to the boat as fast as I could, while still treading slowly and cautiously through the turbid waters. Thankfully, Michele’s cut wasn’t bad and she was able to clean it out with the first aid kit on board. Next time, we are wearing waders!

More stories of oyster and parasite hunting >>

From the Field: Thunderstorm!

Wednesday, July 10th, 2013

by Katrina Lohan

Rainbow over the marsh at Wachapreague, Va., following a storm. (Katrina Lohan)

Rainbow over the marsh at Wachapreague, Va., following a storm. (Katrina Lohan)


A pretty impressive thunderstorm rolled through one night while we were in Wachapreague. We were so close to finishing that we decided to push through and cross our fingers that the power didn’t go out. Michele and Kristy started cleaning up the lab as soon as they finished processing all of the samples for DNA analysis; however, I still had a few more that I needed to scan under the microscope for metazoan parasites.

It was a little eerie to watch the sky darken and hear the wind, especially when the lights in the lab kept flickering. I contemplated stopping, but I had already dissected all of my samples. It took about 30 more minutes, but I was able to finish up and then we made a mad dash for our rooms in the dormitory. While the power stayed on in the lab, the dorms weren’t so lucky.

As soon as the storm was over, we headed out to dinner at a local restaurant. The view over the marsh was spectacular—rainbows everywhere!

From the Field: Microscopic Parasites

Monday, July 8th, 2013

by Katrina Lohan

Microscopic slide of a mussel parasite called a trematode. Trematodes often infect small aquatic animals, like mussels or snails, in hope of getting eaten by a larger host they can infect later. Viewed under 400x magnification. (Katrina Lohan)

Microscopic slide of a mussel parasite called a trematode. Trematodes often infect small aquatic animals, like mussels or snails, in hope of getting eaten by a larger host they can infect later. Viewed under 400x magnification. (Katrina Lohan)

Just as in previous trips, part of our sampling involved dissecting the bivalves and preparing tissue preps to view under the microscope. I have to admit that the microscopic metazoan parasites that I saw on this trip were not quite as exciting as previous trips—I miss the really cute turbellarians (a.k.a. Urostoma sp.)! Though they weren’t as cute, I did see some parasites through the microscope, including trematode metacercariae in the mussels, three marine mites, a handful of pea crabs and free-swimming harpacticoid copepods. I had never seen a marine mite before and at first thought there were ticks running around the lab. That’s what happens when you spend hours in front of a microscope–you forget how small the things you are viewing actually are!

From the Field: Clam Shucking

Wednesday, July 3rd, 2013
Michelle Repetto shucks a hard clam (Mercenaria mercenaria) using a device borrowed from the VIMS Eastern Shore Laboratory. (Katrina Lohan)

Michelle Repetto shucks a hard clam (Mercenaria mercenaria) using a device borrowed from the VIMS Eastern Shore Laboratory. (Katrina Lohan)

by Katrina Lohan

If you have ever tried to open M. mercenaria, then you can fully appreciate that the folks at the ESL gave us a specially designed apparatus just for shucking clams. Even then, the clams we collected were pretty big, so getting them open was really hard.

A co-worker from the Marine Invasions Lab, Michele Repetto, joined Kristy and I on this trip and she has become a master shucker. Between Kristy and Michele’s excellent shucking capabilities, the large clams didn’t stand a chance. Now the mussels on the other hand presented a separate challenge, which was attempting to get them open without destroying the shells, which we are archiving and will eventually submit to the molluscan collection at the National Museum of Natural History.

While I frequently broke the mussel shells into many pieces, Kristy and Michele had the appropriate finesse to open the mussels without causing massive shell damage. Have to enjoy the challenges of working with different species!