Ecology

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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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Wetlands Can Resist Rising Seas, If We Let Them

Thursday, December 5th, 2013

by Kristen Minogue

Fishing camp along Falgout Canal Bayou, La., where marsh has submerged into open water and remains mostly on canal leaves. (Matt Kirwin/VIMS)

Fishing camp along Falgout Canal Bayou, La., where marsh has submerged into open water and remains mostly on canal leaves. (Matt Kirwin/VIMS)

Left to themselves, coastal wetlands can adapt to sea-level rise. But humans could be sabotaging some of their best defenses, according to a review paper from the Smithsonian Environmental Research Center and the Virginia Institute of Marine Science to be published Thursday, Dec. 5 in Nature.

The threat of disappearing coastlines has alerted many to the dangers of climate change. Wetlands in particular—with their ability to buffer coastal cities from floods and storms, and filter out pollution—offer protections that could be lost in the future. But, say co-authors Matt Kirwan and Patrick Megonigal, higher waters are not the key factor in wetland demise. Thanks to an intricate system of ecosystem feedbacks, wetlands are remarkably good at building up soil to outpace sea-level rise. But this ability has limits. The real issue, the scientists say, is that human structures such as dams and seawalls are disrupting the natural mechanisms that have allowed coastal marshes to survive rising seas since at least the end of the last ice age.

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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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Of Censusing Trees and Elephant Dung

Friday, November 22nd, 2013

by Kristen Minogue

Herve Memiaghe, front, in Gabon’s Rabi forest plot. The red line marks where they measure the tree’s diameter. (Smithsonian Institution)

Herve Memiaghe isn’t the average intern. Before coming to the Smithsonian Environmental Research Center, the 33-year-old Gabonese ecologist had already earned a master’s degree and spent four years working at IRET, the Institute for Research in Tropical Ecology in Gabon. Since 2012 he has also done field work in the Rabi plot as part of the Smithsonian’s global forest study.

The 25-hectare Rabi plot sits on the southwest coast of Gabon. Diversity spikes in the rainforests of Central Africa, where a single hectare can contain more than 400 different species. And that’s just the trees. The animals bring problems of their own. In Memiaghe’s experience, it’s not uncommon for hungry elephants to eat the tree tags along with the leaves.

“Sometimes we find the tag in the dung of elephants,” Memiaghe says. Usually the scientists can figure out where the tag came from, so it doesn’t throw off their research that much. “It just maybe can be a mess for the new people.”

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Q&A: The Heart of the Ocean

Tuesday, November 12th, 2013
Before joining MarineGEO, Emmett Duffy did research in waters from Australia to Siberia. (Photo: College of William and Mary)

Before joining MarineGEO, Emmett Duffy did research in waters from Australia to Siberia. (Photo: College of William and Mary)

by Kristen Minogue

It’s “the largest, coolest marine biological project on Earth”, according to its new director, Emmett Duffy. On Sept. 16 Duffy came on board the Tennenbaum Marine Observatories Network, a.k.a. MarineGEO–the Smithsonian’s global network to monitor the oceans. So far it has five stations tracking the ocean’s chemistry and biology, from SERC in Maryland to STRI in Panama. They plan to add at least 10 more in the next decade. Now, after two  months on the job, Duffy shares his vision in this edited Q&A.

What’s the main purpose of MarineGEO?

The overall goal really is a very ambitious one. In my mind, it’s to understand what’s at the heart of how marine ecosystems work…and that is biodiversity. The living web from microbes to large predators that are responsible for ecosystem processes like fish production and habitat creation. So basically what we want to do is map marine biodiversity and what it’s doing across the globe.

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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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Deadly Tricks of Spiders Without Webs

Thursday, October 17th, 2013

by Kristen Minogue

The goldenrod crab spider (Misumena vatia) blends in almost perfectly with the yellow chamomile flower. Goldenrod spiders can change between white and yellow to mimic their surroundings and ambush prey. (Alvegaspar)

The goldenrod crab spider (Misumena vatia) blends in almost perfectly with the yellow chamomile flower. (Alvegaspar)

There’s a reason cobwebs make popular Halloween decorations. Spiders rival with snakes, birds and clowns for the most feared creatures in the animal kingdom. But some of nature’s creepiest arachnids don’t build webs at all. They ambush their prey in much more beguiling settings. Like flowers.

That’s a favorite haunt of the crab spider, one of several groups of webless spiders that hunt, instead of trap, their food. The name comes from their four long front legs, which stretch out like claws, and their crab-like method of walking—they’re better at moving sideways and backwards than forwards. But their strategy for capturing prey has earned them another common name: the ambush spiders.

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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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Methylmercury Microbes More Widespread Than Realized

Thursday, September 12th, 2013
New places scientists discovered can contain the microbes--Archaea and Bacteria--that create the dangerous neurotoxin methylmercury. (SERC & ORNL)

New places scientists discovered can contain the microbes–Archaea and Bacteria–that create the dangerous neurotoxin methylmercury. (SERC & ORNL)

Microbes that live in rice paddies, northern peat lands and beyond are among the several types of bacteria researchers at the Smithsonian Environmental Research Center and Oak Ridge National Laboratory have just learned can generate highly toxic methylmercury.

This finding, published Wednesday in Environmental Science & Technology, explains why methylated mercury, a neurotoxin, is produced in areas with no previously identified mercury-methylating bacteria. Methylmercury—the most dangerous form of mercury—damages the brain and immune system and is especially harmful for developing embryos. Certain bacteria transform inorganic mercury from pollution into toxic methylmercury.

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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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