Invasive Species

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From the Field: High and Dry in Chesapeake Bay

Thursday, December 19th, 2013

How an invasive marsh plant could leave many fishes and invertebrates homeless, hungry and vulnerable to predators

Ecologist Heather Soulen (right) wades through a patch of Phragmites in Chesapeake Bay. (SERC)

Ecologist Heather Soulen (right) wades through a patch of Phragmites in Chesapeake Bay. (SERC)

by Heather Soulen, SERC marine ecology lab technician

It’s no surprise that invasive species can dramatically alter an ecosystem. Often, invasive species outcompete native species and disturb ecosystems that have not evolved to handle the new intruder(s). One such invader is the introduced common reed (Phragmites australis australis). Introduced Phragmites alters native plant communities that native animals use. Over the past several decades, native marshes containing plants such as marsh elder, saltmeadow hay, black needlerush, sea lavender, cordgrasses, threesquares and bulrushes have fallen to introduced Phragmites in the Chesapeake Bay and throughout the Atlantic coast, turning once diverse marshes into a thick monoculture forest.

The Great Marsh Surface Uprising
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Intern Logs: Acoustic Telemetry
and Catfish Surgery

Friday, December 6th, 2013

by Brooke Weigel

Brooke Weigel displays a recently-caught blue catfish in SERC's Fish & Invertebrate Lab. (Katie Sinclair)

Brooke Weigel displays a recently-caught blue catfish in SERC’s Fish & Invertebrate Lab. (Katie Sinclair)

Have you ever wondered how far a fish can swim in one day? Acoustic telemetry enables researchers to track the movement, migration and behavior of fish. Beginning this past summer, the Fish and Invertebrate Ecology Lab started using acoustic telemetry to study the movement patterns of invasive blue catfish in the Patuxent River, a tributary of Chesapeake Bay.

Native to the Mississippi River, blue catfish were introduced for sport fishing in Virginia in the 1970s. Since introduction, these non-native top predators have expanded their range into many of Maryland’s tributaries. Their voracious appetites affect native fish populations and disrupt the food webs in these rivers. Blue catfish are the largest and most migratory species of catfish in North America. In their native waters, blue catfish have been known to migrate up to 200 km between different habitats used for spawning, feeding and overwintering. But little is known about their movement patterns within the Chesapeake Bay watershed, which is our motivation for using acoustic telemetry to track the movements of individual blue catfish.

Similar to radio tracking used to locate animals over vast distances, acoustic telemetry is a two-part system: Each fish has a transmitting tag, which emits a unique series of underwater sounds or “pings” at a random interval every one to three minutes. Stationary receivers then detect and decode these pings whenever a fish swims within range of the receiver. These detection data are converted to digital data and stored until researchers download the data onto a computer.

Interning at SERC for the past six months has given me the opportunity to be involved in every step of the process—some of which were messier than others.

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From the Field: The Mysterious Mangroves
of Baja California

Wednesday, November 27th, 2013

by Cora Ann Johnston

Mangroves in the desert of Baja California, Mexico. ( L. Simpson).

Mangroves in the desert of Baja California, Mexico. ( L. Simpson).

Get ready

Researcher Mike Lehmann makes his way through dwarf-form mangroves in the Gulf of California. (C. Johnston)

Researcher Mike Lehmann makes his way through dwarf-form mangroves in the Gulf of California. (C. Johnston)

As you approach stands of mangroves in Florida, you’re likely to notice a few things. They form expansive forests along protected seashore (usually in lagoons and estuaries) that often grow thick and tall overhead, providing welcome shade where the three species (black, white and red) intermingle. In the cool of their shade, they are clearly teeming with life; the constant pop of snapping shrimp ricochets around their oyster- and barnacle-encrusted roots while crabs and insects scurry along their branches.

These mangroves are different. There are no scurrying crabs or snapping shrimp or prominent rocks of oysters. Most of the insects have gone inside; their only traces are burrows and cocoons made in the safety of stems and rolled leaves. The blinding sun and gusty wind make it starkly obvious that the shady, protective canopy is only waist-high. The cactus on the rocky slope in the background gives it away: These mangroves are in Baja California, Mexico.

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Volunteers Search for Invaders in Alaska Bioblitz

Monday, October 28th, 2013

by Monaca Noble, Kristen Larson, Linda McCann and Ian Davidson

Video: Biologists place pennies underwater to test how well volunteers can spot small invaders

What is the Bioblitz, and why would researcher Linda McCann cash in her dollar bills for hundreds of pennies in preparation for it?

Bioblitzers braved the rain to search for invasive species. (Deborah Mercy)

Bioblitzers braved the rain to search for invasive species. (Deborah Mercy)

A Bioblitz is an intensive survey in which trained volunteers head out en masse to catalog species in a specific area. On September 28, volunteers in Ketchikan, Alaska, joined staff from the Smithsonian Environmental Research Center (SERC), San Francisco State and the University of Alaska to search for invasive marine species along Ketchikan’s waterfront. The Marine Invasive Species Bioblitz in Ketchikan had three goals: to engage and teach the public about invasive species, detect newly arriving species that threaten Alaskan coastal waters, and recruit these enthusiastic volunteers for future monitoring efforts.

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Decoding Nature: How DNA Can Save Species

Tuesday, September 17th, 2013

by Katie Sinclair

Katrina Lohan and Kristy Hill collect oysters on rocks near Punta Chame, Panama. (Carmen Schloeder)

Katrina Lohan and Kristy Hill collect oysters on rocks near Punta Chame, Panama. (Carmen Schloeder)

Katrina Lohan and Kristy Hill have travelled thousands of miles down the Atlantic Coast, from the Chesapeake to the Caribbean. Their goal? Track the range and distribution of parasites in bivalve mollusks that could cause disease. Based on diversity patterns, Hill and Lohan suspect that there are many more protist species in the tropics than have previously been discovered. These parasites could be very similar to the parasites that have caused mass die-offs in Chesapeake oyster beds with diseases like Dermo and MSX.

Close-up of a trematode oyster parasite. These parasites form cysts, and could be similar to the parasites that caused mass die-offs in the Chesapeake.

Close-up of a trematode oyster parasite. These parasites form cysts, and could be similar to the parasites that caused mass die-offs in the Chesapeake.

But there’s one catch: The protists that are parasitizing the bivalves are difficult to identify just by looking at them. Luckily for Lohan and Hill, advances in DNA sequencing can reveal secrets about little-studied and poorly understood organisms. Already famous for helping improve human health, DNA sequencing is proving equally adept at preserving the planet’s health. From the tropics of Panama to the forests of Maryland, the rise in DNA sequencing is opening new realms of possibility for ecologists at the Smithsonian Environmental Research Center and across the world.

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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 >>