Invasive Species

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From the Field: Mangroves, Salt Marshes and Hungry Insects

Wednesday, September 11th, 2013

by Lily Durkee

Spotted-winged grasshopper, one of two insect herbivores the team tested to see if they would eat mangrove leaves. (Alex Forde/UMD)

Spotted-winged grasshopper, one of two insect herbivores the team tested to see if they would eat mangrove leaves.
(Alex Forde/UMD)

After spending five weeks working indoors as a research intern at the University of Maryland in College Park, walking out into the salt marsh at the Guana Tolemato Matanzas (GTM) Reserve in Florida was a welcome change of scenery. The sky was a crystal clear blue, egrets and herons soared overhead, and crabs scuttled haphazardly on the sand as we waded into the cordgrass, ready for a hard week of field work.

My mentor, Alex Forde, and I were there conducting experiments for his dissertation and for my internship project. This whole summer we had been studying plant resistance to herbivores, so we were excited to document interactions between leaf-eating insects and black mangrove trees (Avicennia germinans) in Northern Florida salt marshes.

Over the past several decades, climate change has allowed black mangroves to move north along the Florida coastline. As a result, they are invading salt marshes and coming into contact with novel herbivores that are not common in mangrove forests further south. Depending on the behavior and food preferences of marsh herbivores, these species may affect how fast mangroves spread into salt marshes and where the trees are able to survive within marsh landscapes. Therefore, we wanted to test (1) whether salt marsh herbivores will eat mangrove leaves when marsh plants are also available, and (2) if salt marsh herbivores show a preference for leaves of different ages or for trees growing in different habitats.

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There’s No “I” in Bryozoan

Friday, August 23rd, 2013

By Katie Sinclair

An illustration depicting bryozoans from Ernst Haekel's The Art of Nature (photocredit: wikipedia)

An illustration depicting bryozoans from Ernst Haekel’s The Art of Nature (photocredit: wikipedia)

All for one and one for all is a motto that bryozoans would take close to heart, if they had hearts, that is. This phylum is made up of 4,000 or so species, almost all of which are colonial. Individuals, called zooids, can’t survive on their own and depend on their fellow colony members to help gather nutrients, get rid of waste, and reproduce. Though sedentary as adults (a few species are able to creep slowly), bryozoans are able to spread through the dispersal of larvae in the water column. If a piece of the colony is broken off, it can survive and form a new colony. Known commonly as “moss animals” most bryozoans live up to the name, resembling robust pond scum. Some species, such as those in the Watersipora genus, form leaf-like, calcareous colonies that can serve as habitat for other animals. Click to continue »

From the Field: Lizards, Spiders and Mangroves

Tuesday, August 6th, 2013

by Micah Miles, SERC intern and UMD undergraduate

If you have ever visited coastal Florida, you have probably run across some lizards. Lots of them.

Green anole seen near the Smithsonian Marine Station. Scientists aren't sure whether anoles are helping or hurting mangroves in Florida. (Micah Miles)

Green anole seen near the Smithsonian Marine Station. Scientists aren’t sure whether anoles are helping or hurting mangroves in Florida. (Micah Miles)

From the moment I arrived at the Smithsonian Marine Station, I quickly became fascinated by the hundreds of anoles I had seen sunning themselves on both the brick walls of the more developed areas and mangrove trees of the state parks. As an intern, I spend five to six days a week meandering through mangrove stands and gazing at black mangrove flowers to document pollinators and other floral visitors. But after seeing over six anoles on just my first day in the field (and after several failed attempts to catch one and observe it up close) I decided to find out what role these lizards could be playing in the mangrove ecosystem.

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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!