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Cracking Down on Mercury

Monday, December 9th, 2013

by Kristen Minogue

Ally Bullock, a technician in SERC's mercury lab, draws pore water samples from Berry's Creek. (SERC)

Ally Bullock, a technician in SERC’s mercury lab, draws pore water samples from a mid-Atlantic Superfund site. (SERC)

There are places in the U.S. so polluted, eating fish or crabs from their waters isn’t just unhealthy—it can be illegal. The Environmental Protection Agency calls sites like that “Superfund sites,” a label for abandoned or neglected sites that became dumping grounds for hazardous waste. Some of the highest levels of mercury contamination in the U.S. exist in Superfund sites. Cynthia Gilmour knows this first-hand. As a microbial ecologist at the Smithsonian Environmental Research Center, she has worked in several.  But short of digging up the polluted sediments and dumping them elsewhere (an expensive and ecologically risky proposition), not many methods exist to get rid of the problem.

“If we use the traditional technologies of removing that and putting it in a landfill, we don’t have a wetland anymore,” says Upal Ghosh, an environmental engineer from the University of Maryland, Baltimore County, who works with Gilmour.

This fall, Gilmour and Ghosh explored a new technique: using charcoal to trap it in the soil.

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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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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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Franken Phrag: Tales of a Super Invader

Thursday, August 29th, 2013

By Katie Sinclair

These chambers at Kirkpatrick marsh allow the amount of CO2 and nitrogen to be manipulated, allowing researchers to understand how climate change will affect the growth of Phragmites.

These chambers at Kirkpatrick Marsh allow the amount of CO2 and nitrogen to be manipulated, allowing researchers to understand how climate change will affect the growth of Phragmites.

An invasive reed from Europe is conquering marsh habitat throughout the Chesapeake, displacing native marsh grasses and drastically changing the face of the wetlands. Phragmites australis, a “jack and master” plant  grows to nearly 10 feet tall and is adept at extracting nutrients from the soil, outcompeting native Phragmites genotypes. Climate change could increase the spread of this invasive plant. But other human activities, such as development, shoreline hardening and agriculture, could also determine the spread and range of Phragmites.

Climate Change Spurs Phragmites Growth

Rachel Hager, who interned with the Biogeochemistry lab, wanted to see if human activities were giving Phragmites even more of a competitive edge. Excess nitrogen from agriculture and industry, as well as increased CO2 levels, could increase Phragmites growth. Working in the Global Change Research Wetland (GCReW), she tracked the growth of  Phragmites under conditions that had more CO2 added, more nitrogen added, and both CO2 and nitrogen added.  She found that CO2 and nitrogen led to increased Phragmites growth, and plots with both CO2 and nitrogen grew the most.

Increased growth is only part of the story, however. Rachel wanted to see if taller Phragmites would inhibit other plants’ access to light. She analyzed leaf length, number, thickness and canopy cover to see if Phragmites exposed to additional CO2 and nitrogen were better at blocking light from their competitors. She found that Phragmites exposed to more CO2 and nitrogen had more, thicker and longer leaves, but their canopy cover was the same as control Phragmites plots. Thicker, longer leaves could lead to a longer leaf lifespan and more leaf litter, however, which could still block other plant’s access to light. Rachel hopes to see further research done on the amount of light that makes it through a Phragmites canopy.
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Sonar Reveals Underwater World

Friday, August 16th, 2013

By Katie Sinclair

A short DIDSON clip of a cownose ray swimming near the SERC dock

One of the biggest challenges of studying life in the Chesapeake Bay is poor visibility. In the water, you literally can’t see your hand in front of your face. So how do you see what’s going on under the water? Sampling with nets can give us a pretty good picture, but if you want to observe what’s happening at a specific moment you need to use another approach.

The Fish and Invertebrate Ecology Lab is using Dual-frequency Identification Sonar (DIDSON) to see what their eyes can’t. The DIDSON uses sound to sketch a picture of the environment much like a fish-finder or depth-finder on a boat. When sound hits an object in the water or the bottom, it bounces back. The result is video footage that can be downloaded and later analyzed. The resolution of the image is pretty impressive, considering it’s the product of sound waves. Many species can be identified by their distinct shapes and movement patterns, and their sizes can be estimated. DIDSON was first developed for the military to locate enemy swimmers , but is now being used as a handy tool by anyone who needs to see in murky waters.

River Herring

A still of a river herring (center) swimming past DIDSON

A still of a river herring (center) swimming past DIDSON

The Fish and Invertebrate Lab started using DIDSON with the goal of better understanding the size of river herring populations in Chesapeake Bay. Funded jointly by the National Fish and Wildlife Foundation and the Smithsonian Institution, the project aims to generate accurate population counts of river herring in the Choptank and Nanticoke Rivers. Once a species that supported a major fishery on the Atlantic coast, river herring (actually two species known as alewife and blueback herring) have declined dramatically over the past 10 years. In order to figure out the best way to conserve and manage these populations, the first step is to figure out how many herring are out there. The murky waters and large run sizes make it nearly impossible to get an accurate visual count. Other methods, such as electrofishing and looking at icthyoplankton (fish eggs and larvae) can potentially work as counting methods, but first it must be established how accurate they really are. By deploying the DIDSON during the spring herring runs, footage of the runs can be recorded and the number of fish counted. DIDSON also allows fish to be recorded for several months straight without requiring someone to be out in the field sampling all day and night.
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DNA Barcodes Identify Chesapeake Species

Friday, July 19th, 2013

By Katie Sinclair

Researchers on a jon boat in the middle of the Patuxent River were very excited to find a rainwater killifish in their crab tow. While not the juvenile crabs that the scientists were looking for, the inch-long rainwater killifish was an intriguing find: It was yet another species that could be “barcoded.”

(stock photo)

(stock photo)

Barcoding is another technique to answer the age-old question of what exactly lives in the Chesapeake Bay. By using trawls, seines and a fish weir, researchers at the Smithsonian Environmental Research Center (SERC) have a pretty good idea of what swims in our rivers and bays. But new DNA technology could give an even clearer picture on what species are present, as well as their role in the estuarine ecosystem.
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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.

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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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Invaders’ “Away-Field Advantage” Not as Strong as Once Thought

Thursday, May 16th, 2013

Brown tree snakes (Boiga irregularis) caused the local extinction of more than half of Guam's native birds and lizards after it invaded the island in the 1940s. (National Park Service)

Brown tree snakes (Boiga irregularis) caused the local extinction of more than half of Guam’s native birds and lizards after they invaded the island in the 1940s. (National Park Service)

by Kristen Minogue

For decades, ecologists have assumed the worst invasive species—such as brown tree snakes and kudzu—have an “away-field advantage.” They succeed because they do better in their new territories than they do at home. A new study led by the Smithsonian Environmental Research Center reveals that this fundamental assumption is not nearly as common as people might think.

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Weddell Seals Have Most Adult-Like Brains of any Mammal at Birth

Thursday, May 2nd, 2013

by Kristen Minogue, Regina Eisert and Olav Oftedal

Because they must lean to navigate under sea ice in just over a month, baby Weddell seals are born with near adult-sized brains. (Samuel Blanc)

Because they must learn to navigate under sea ice in just over a month, baby Weddell seals are born with near adult-sized brains. (Samuel Blanc)

When it comes to brain size, Homo sapiens generally get the most credit. But to find the baby mammals with the proportionally largest brains on the planet, Smithsonian scientists had to search in Antarctica. In a study published online in April, they found Weddell seal pups have the most developed brains at birth recorded for any mammal so far.

By the time they are born, baby Weddell seal brains have already reached 70 percent of their adult size. (The brain of a human infant is a mere 25 percent of its adult size.) But the researchers found this rapid development carries a hefty price tag.

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