Parasites and Suicidal Shrimp

Posted by KristenM on August 21st, 2013

By Katie Sinclair

A grass shrimp infected with a trematode parasite (photo: Sara Gonzales)

A grass shrimp infected with a trematode parasite (photo: Sara Gonzalez)

While the idea of playing host to something out of the movie Alien is decidedly unpleasant, it’s hard not to marvel at theexquisite grossness of microscopic parasites. Parasites take advantage of their hosts for resources and shelter, but research on parasites suggests that they also can manipulate their hosts’ behavior: Crickets will drown themselves, snails position themselves to be eaten by birds, and some theories suggest that cat-lovers infected with the parasite Toxoplasma gondii become self-destructively reckless.  More than half the known species in the world are parasites—making parasitism the most popular lifestyle on Earth.

At the Smithsonian Environmental Research Center (SERC), the Marine Invasions Lab has been tracking parasites in grass shrimp, an incredibly common near shore species. Rates of parasitism are extremely high in grass shrimp, with some years 90 percent of the shrimp caught displaying parasite infection. The most common parasite is a trematode that forms cysts in the tail of the shrimp. Sara Gonzalez, who interned with SERC this summer, wanted to see if parasitized shrimp displayed different predator avoidance behaviors than unparasitized shrimp. Because the trematode only reproduces in birds and mammals, the parasite must find a way to make its way up the food chain. Sara suspected that infected shrimp will change their behavior  in a way that makes them more vulnerable to predators like mummichogs. The parasite does not infect the mummichogs directly, but mummichogs are prey for mammals and birds. If a mummichog that has ingested an infected shrimp gets eaten by a bird or mammal, then the parasite will be able to reproduce.
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Are You Smarter Than a SERC Visitor?

Posted by KristenM on August 21st, 2013

By Katie Sinclair


Boats, beavers. . .and bear poop? If you want to see what our campers learned this summer, take this quiz below and see how you measure up!

Are You Smarter Than a SERC Visitor? Quiz

As store aisles quickly fill up with back to school supplies, SERC’s summer education programs are coming to a close. SERC’s Education Team took a slightly different approach to summer programming this year. Instead of hosting summer camps, they sponsored three “activity weeks” throughout the summer. Each activity week had a specific theme, and was tailored to different age groups. The first of SERC’s activity weeks was “Changing Environments,” designed for students aged 13-15. The week focused on certain case studies that highlighted environmental changes. The students also visited SERC’s weather tower, and went on expeditions in the SERC forest to catch insects and frogs. “Kids Unplugged”, the next week, was made up of students aged 7 to 9. One of the more memorable lessons was when the kids made “scat” out of play-doh in order to better understand the types of birds and mammals that live in the SERC forest.  The last activity week, “Junior SERC Scientists” introduced 10-12 years olds to problem solving and the scientific method. They used  forensic clues to discover who “killed” a beaver. The kids put their sleuthing skills to the test and found that the murderer was none other than Education Intern Shelby Ortiz!


Sonar Reveals Underwater World

Posted by KristenM on 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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Trees, Poison Ivy and Climate Change

Posted by KristenM on August 12th, 2013

By Katie Sinclair


Intern Hope Zabronsky measures the diameter of a tree to see how logging affects biomass regeneration

Summer is almost over, which means intern season is coming to a close. Over 20 interns from universities across the United States have spent their summers here at SERC, studying everything from phytoplankton to Phragmites. Several interns chose to take on the challenge of climate change, exploring how trees will affect rising levels of greenhouse gases.

Mysterious Methane

Although methane emissions worldwide are much lower than CO2 emissions, a little methane goes a long way: Methane is 25 times as powerful a greenhouse gas as CO2. While we have an idea of what the sources of methane are, researchers face difficulties when trying to model methane emissions. The biggest discrepancy is between “top-down” and “bottom-up” models. Top-down approaches use satellite imagery to track the amount of methane in the atmosphere, while bottom-up methods look at the amount of methane emitted from the soil.
The Biogeochemistry Lab wants to see if methane is coming from sources other than the soil. Marsh grasses are known to emit methane, but no research has yet been done on trees. Figuring out if and how much methane is emitted can help determine whether methane projections are accurate. The Biogeochemistry Lab has set up two experimental sites to study methane, and is working on establishing a third.

Intern Kyle King worked on methane emissions this summer. He attached airtight chambers to trees, and measured the gas concentrations at different heights along the tree. He found that trees did emit methane, in some cases more than microbes in the soil. Methane emissions were highest near the roots and less at higher trunk heights. He also found that larger trees emitted much more methane than smaller ones.

The exact mechanism of how trees release methane is not yet understood. Two possibilities are methane diffusing out of the water that is taken in by the plants’ roots, or microbes inside the tree producing methane. But whatever the cause, understanding where methane comes from will be vital when trying to predict the impact of climate change.
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From the Field: Lizards, Spiders and Mangroves

Posted by KristenM on 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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The Crab Tow Tango

Posted by KristenM on July 29th, 2013

by Katie Sinclair

Brooke and Paige get ready to deploy the tow.

Brooke and Paige prepare to deploy the tow.

There is a certain art to the deployment of a crab tow. This brown metal and net contraption, about three feet long and a foot wide, scrapes over the bottom in search of juvenile blue crabs. Fitting three people, two coolers, a selection of buckets and bins and the tow in a 16-foot jon boat is something akin to a giant game of Tetris. Successfully launching and recovering the crab tow without smacking anyone in the face or knocking anything overboard requires practiced choreography and grace.

With a one-two-three, the metal tow hits the water with a splash. After 300 feet, lab tech Paige Roberts gracefully maneuvers the jon boat backwards and forwards to retrieve the tow. Paige captains the jon boat a bit like a fighter pilot—precision is required to coax the unwieldy boat around shoals, patches of sea grass and oblivious jetskiers. Click to continue »


Hunt for a Missing Nutrient: Part II

Posted by KristenM on July 24th, 2013

By Katie Sinclair

Alyssa and Carey begin their search for key nutrients in a stream in the Choptank Watershed.

Alyssa and Carey begin their search for key nutrients in a stream in the Choptank Watershed.

The nutrient lab is still plagued by the mystery of the missing nitrogen. More nitrogen enters the watershed than exits it, and the question remains: Why?

How much nitrogen makes it to the bay can have huge impacts on the water quality and bay health. The Choptank watershed, in a farm-heavy area, has much lower levels of nitrogen in stream water than expected. As farmers add fertilizer to their crops, some nitrogen gets taken up by the plants, and the rest washes away into the watershed , eventually reaching the Chesapeake Bay. Of the nitrogen that is added as fertilizer, only 20 to 30 percent of it is accounted for.

In a narrow, slow-moving stream in the Choptank watershed, fondly nicknamed “Pizza Branch” (due to its proximity to a lone pizza joint puzzlingly located in this predominantly farming area), researchers working under Tom Jordan, Principal investigator of the nutrient lab at SERC, are using different methods to help determine what’s happening to the nitrogen. The project is a joint effort between SERC and Tom Fisher’s lab at the Horn Point Laboratory of the University of Maryland.

Researchers brave high heat, humidity, and voracious mosquitoes to take water samples, a process that can take all day. While taking water from a stream may seem like a straightforward undertaking, the true complexity comes through in the lab, where analysis of microscopic dissolved compounds can reveal the secrets of a watershed.

“It’s a fun challenge to go all over a stream and take samples and bring them back to the lab, to discover things you can’t see with your eyes,” said Jordan.
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From the Field: Out of the Mangrove and into the Marsh

Posted by KristenM on July 22nd, 2013

by Megan Riley

University of South Carolina Ph.D. student; Smithsonian Marine Station visiting scientist

Mangrove tree crabs crowd onto a dwarf red mangrove, in a hybrid mangrove-marsh region. (Megan Riley)

Mangrove tree crabs crowd onto a dwarf red mangrove, in a hybrid mangrove-marsh region. (Megan Riley)

Home for most species largely depends on climate: temperature, light and rainfall. With changes in global climate trends, many plants and animals are expanding their geographic limits poleward. However, not all species in a community respond to these changes in the same way.

Organisms often differ in the type and timing of their responses to environmental changes. Sometimes, animals expand more quickly than the habitats they’re used to. When this happens, these organisms are forced to colonize unfamiliar habitats where they often face numerous challenges, like resource shortages and never-before-seen predators.

So how do these animals alter their behavior, resource use and reproductive strategy to succeed in their new habitats? I aim to explore just that question by studying the range expansion of the mangrove tree crab Aratus pisonii into salt marsh habitats.

Mangrove tree crab Aratus pisonii on a black mangrove tree. (Megan Riley)

Mangrove tree crab Aratus pisonii on a black mangrove tree. (Megan Riley)

Mangrove tree crabs are native to Florida and abundant throughout Floridian mangroves, where they are the dominant herbivores of fresh mangrove leaves. Like mangrove trees, they have slowly begun moving northward. But the crabs are moving faster than the mangroves—and they’ve begun to invade salt marsh territory. They can be found crowding onto isolated dwarf mangroves nestled amidst cord grass, as well as in salt marshes with no mangroves in sight!

How mangroves are taking over marshes

Because mangrove tree crabs in their native habitats rely heavily on mangroves for food and shelter, their habitat shift into salt marshes also causes a diet shift that can impact their growth, survival and reproduction. By focusing on the range expansion of mangrove tree crabs into salt marshes during my time at the Smithsonian Marine Station this summer, I hope to shed light on what exactly is enabling this species and countless others to successfully expand their range into new environments.


DNA Barcodes Identify Chesapeake Species

Posted by KristenM on 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

Posted by KristenM on 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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