Ecology

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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.

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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!

From the Field: Oysters from Oyster

Tuesday, July 2nd, 2013

by Katrina Lohan

Seaside Hall at the VIMS Eastern Shore Laboratory, where Katrina Lohan and Kristy Hill spent most of their time taking samples from bivalves. (Katrina Lohan)

Seaside Hall at the VIMS Eastern Shore Laboratory, where Katrina Lohan and Kristy Hill spent most of their time taking samples from bivalves. (Katrina Lohan)

The end of our field season (if you call half a year a field “season”) is coming to an end as we now head for our sampling location in the Chesapeake Bay. Our northernmost sampling location is Wachapreague, Va., located on the Delmarva Peninsula and home of the Eastern Shore Laboratory (ESL) of the Virginia Institute of Marine Science (VIMS).

Kristy and I are both alumnae of the College of William and Mary and conducted our graduate research at VIMS. For my Ph.D., all of my fieldwork was conducted at the ESL, so returning as a postdoc, working on a different disease system, is a little surreal for me. It has been nice to catch up with the folks at this lab and see the new buildings, which were still in preparation when I graduated. How time flies!

Before venturing out on this particular trip, we contacted our collaborator Ryan Carnegie of the Shellfish Pathology Lab at the Virginia Institute of Marine Science to get some suggestions about sampling location. He suggested sampling oyster reefs at Mockhorn Channel just off Oyster, Va., as they had historical data from that area. The folks at the ESL knew just where to take us and we headed out on Tuesday to collect.

In previous locations we aimed to collect three oyster species. However, there is only one oyster in the Chesapeake Bay: Crassostrea virginica, the eastern oyster. So we decided to collect other bivalves: the ribbed mussel (Geukensia demissa) and the hard clam (Mercenaria mercenaria).

Our boat captain, Edward Smith, suggested that we split up so that we could complete the collection prior to the tide coming in. I ended up on the high marsh searching for mussels, which was super muddy and, consequently, lots of fun! It was beautiful weather and just windy enough that the bugs stayed away. Once all the mussels and oysters were collected, we all headed to a mud flat to rake for clams. I have to admit that I am horrible at finding clams. While Edward found more than 30 clams, I found three….Good thing that others were better than me or we would never have found enough. Then it was back to the lab to figure out how to shuck them all!

Stomachs, Ear Bones and Electrofishing: Dissecting the Invaders

Friday, June 28th, 2013

By Katie Sinclair

SERCterms Mark and Brooke weigh and measure a bluecatfish.

SERC interns Mark and Brooke weigh and measure a blue catfish.

Ever wonder what a catfish eats? The blue catfish, invasive to the Chesapeake, is not a picky eater.

This voracious predator eats pretty much anything that can fit in its mouth.  By digging into their stomachs, a process vaguely reminiscent of high school biology classes, researchers can figure out the impact this species has on the ecosystem.

 In order to get some fresh catfish stomachs, researchers working in the Fish and Invertebrate Lab at SERC set up a “Gon’ fishing” sign and hit the field.

 Using a technique known as “electrofishing,” researchers stun the fish with electric currents in the water and collect them from several sites along the Chesapeake and rivers that feed into the Bay. Once the fish are caught, they place them into a cooler. The frozen fish are then identified by species, weighed and measured. Each fish varies tremendously: From a few ounces to over 10 lbs., a wide range of maturities and sizes are represented.

Paige and Mike begin to dissect the fish.

Paige and Mike begin to dissect the fish.

 A closer look at the stomach

A closer look at the stomach

The ecologists then remove the fish’s stomach,  taking great care to keep it intact. (Though frozen, the contents of a fish’s lower intestines tend to have a rather unpleasant smell). As fishermen know, gutting catfish can get messy, especially when the interns get involved.

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Marsh Rovers: Research at the SERC Marsh

Thursday, June 27th, 2013

By Katie Sinclair

If you take a stroll out along the green grated catwalk that lies several feet above the muddy marsh ground at SERC, the first thing you’ll notice is strange white structures dotting the lush landscape. No, the aliens haven’t landed. These white enclosures make up several experiments at SERC. The goal of each experiment is to determine how a changing climate will affect this valuable marsh habitat, which stores carbon, has high primary productivity, and provides homes for fish, crustaceans, insects,  and more.

The SERC marsh. Under each treatment, conditions are set to mimic the CO2 concentration expected in 2100. (Credit: Thomas Mozdzer)

The SERC marsh. Under each capsule, conditions are set to mimic the CO2 concentration expected in 2100.
( Thomas Mozdzer)

Carbon and Nitrogen: Elements of Growth

Since 1987, SERC scientists have been pumping CO2 into these plastic chambers to simulate the marsh a century from now—a marsh in the grip of climate change. Inside these miniature time capsules, marsh plants grow with 350 parts per million more CO2 than is in the atmosphere today, levels scientists expect to see by the year 2100.  As marsh plants grow, they take in CO2 from the air. This carbon can either end up sequestered in the soil or released back into the ecosystem through decomposition. The CO2 addition experiments conducted at SERC are the longest-running in the world.

Besides carbon, marshes also rely on nitrogen, an element necessary for the creation of proteins. Due to runoff from fertilizers, nitrogen levels are also increasing in estuaries like the Cheasapeake Bay. As the concentration of both CO2 and nitrogen increases, scientists at SERC are asking important questions about how the structure of the marsh will be affected, including how it will change the plant communities that will grow there.

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From the Field: Sleepless Nights and Road Trips

Tuesday, June 25th, 2013

by Cora Johnston

When studying major ecological changes, like the movement of entire species or ecosystems, we often have to sample across large geographic areas. This means lots of road trips!

Taking a moment to reflect after a field day that started at midnight. (Cora Johnston)

Taking a moment to reflect after a field day that started at midnight. (Cora Johnston)

Starting nearly two months ago, I began my own road trips along the coast to survey the larval crabs that are washing ashore in swarms. Crabs typically recruit (leave the open ocean as larvae to join adult populations in coastal habitats) in a few brief but frenzied weeks in late spring and early fall. Therefore, I’ve been busy hopping between sites to gather as much data as I can while the crabs are abundant. Unfortunately, this means that my schedule, like the crabs’, depends on moonlight and tides. I’ll wake up around midnight, drive until the wee hours of the morning, and then sample the incoming tides by moonlight until wrapping up and moving to my next site as the sun rises. I then load up a kayak and spend the day paddling around collecting larger crabs (though still far too tiny to eat) from deep in each habitat to compare to the larvae I find riding the currents at night.

I head off on these adventures wielding stacks of audiobooks, a hefty thermos and lots of pre-labeled jars and data sheets that ease the demands on a weary mind. I munch trail mix to battle the exhaustion and swim to soothe the bug bites. After a few weeks on this schedule, even I find it hard to believe that I will get up at midnight the very next week to start all over again. Luckily, what keeps me coming back is what got me out of bed to do these studies in the first place.

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