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
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. Click to continue »
Posted in Publications | Comments Off on Sonar Reveals Underwater World
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)
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. Click to continue »
Posted in Publications | Comments Off on DNA Barcodes Identify Chesapeake Species
“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.
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.
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.
by Kristen Minogue, Regina Eisert and Olav Oftedal
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.
Lumbricus rubellus, a European earthworm that is now one of the most common in the eastern U.S. More than 10,000 years ago, Pleistocene glaciers wiped out native earthworms. Today virtually all earthworms in the U.S. north of Pennsylvania are invasive. (Holger Casselmann)
Most gardeners consider the sight of an earthworm writhing in the dirt a good omen. The slimy invertebrates chew up and churn up the soil, making it easier for vegetables and flowers to access nutrients.
But for wild orchids, they’re more of a menace. Earthworms could prevent roughly half a forest’s orchid seeds from even germinating, ecologists from Smithsonian Environmental Research Center and Johns Hopkins University discovered in a study published online this March in Annals of Botany Plants.
The small size of orchid seeds (they are barely the size of dust grains) makes them particularly vulnerable. As earthworms chew up forest litter, they ingest orchid seeds as well. When that happens, two things can keep the seeds from germinating: One, the process of passing through an earthworm’s gut can render them unviable. Or two, if the seeds survive ingestion, they can end up buried so deep that they can’t access the fungi they need to germinate and grow. As a general rule, deeper soils are much less likely to have those fungi.
The scientists and interns who planted BiodiversiTREE in 2013, along with roughly 100 volunteers. From left: Susan Cook-Patton, Whitney Hoot, Caitlyn Cecil, Jess Shue, John Parker, Kim Holzer and Lada Klimesova. (Credit: Susan Cook-Patton)
An Irish-Canadian farmer once told his son that the true meaning of life was to plant trees under whose shade he did not expect to sit. It’s a proverb many altruists and humanitarians have taken to heart, though not all as literally as John Parker.
In March, Parker began planting an entire forest. If things go as planned, that forest will become the longest-running field experiment in SERC’s history—an experiment he will not live to see completed.
His lab works in Watershed 109, an expanse of brown field that grew nothing but corn for the last three decades. The core five-person team consists of Parker, postdoc Susan Cook-Patton, field aids Whitney Hoot and Lada Klimesova, and intern Caitlin Cecil. They’ve been outside overseeing volunteers seven days a week since March 4, with only two days off for harsh weather. One day it rained, sleeted and snowed with winds up to 40 miles per hour. That day wasn’t one of them.
There’s an art to planting saplings, Hoot explains. The holes need to be completely filled with soil so infant trees don’t drown in a well of rainwater. Occasionally they have to trim what Hoot calls “suicidal” trees, whose roots curve upward into a J.
Whitney Hoot, project coordinator for BiodiversiTREE, plants a new sapling in a former cornfield. (Credit: Kristen Minogue/SERC)
“It will grow along the surface instead of growing down, and it just can’t get enough water,” Hoot says. “And so rather than killing the tree immediately, it will take a couple of years. And that’s really bad for our experiment.”
Then, once they’re in the ground, there’s the matter of watering all 18,000 saplings. “In a perfect world, it would rain every day for 45 minutes and get sunny again, but that ain’t gonna happen,” Parker says.
But the labor pains of birthing the new forest will pass. When they do, Parker and the ecologists after him will have something priceless: the chance to watch it evolve over a century or longer.
Project BiodiversiTREE
The name BiodiversiTREE comes from the key question Parker wants to answer: Is a diverse forest a better forest? Are trees more likely to survive surrounded by other species? Will it shelter more animals? And will it do more for people, filtering out our pollutants and absorbing our carbon?
There’s reason to think it will. Different tree species have different root systems. Grouping them together minimizes competition for water and nutrients—and increases the odds of them stopping harmful chemicals before they reach Chesapeake Bay. Tasty plants stand a greater chance of not getting eaten if they hide among less palatable ones. And a forest with more plants that survive, period, will do a much better job soaking up CO2.
John Parker circles a kapok tree in Panama. Panama’s forests shelter over 400 tree species. Parker wants to find out if biodiversity is just as important in the temperate zone. (Credit: SERC)
The project is one of just a handful in the world like it, and the largest in North America. The Smithsonian has two experimental forests in Panama. By comparing them, ecologists can find out if diversity matters as much in the temperate zone as it does in the tropics, where researchers have roughly 400 tree species to work with. Perhaps it matters more.
“If you have four hundred, you’ve got a lot of extra rivets to hold that plane together,” Parker says. “Here, you’ve got 30, 35. But if you look at the distribution of species, it’s dominated by two or three.” If just one species falls by the wayside—like the tulip poplar—it could drastically alter the ecosystem.
But to test that, the team needs to design the forest carefully. They have divided the farmland into 35-by-35-meter plots. Each plot can hold 255 trees, and they have 16 species to choose from. Cook-Patton, Parker’s postdoc, is in charge of deciding which trees go where. Some will contain only oak or beech or red maple. Others will contain mixtures of four or 12 different species. And five plots will be left to regrow naturally. By the time it’s finished, a mosaic of 75 forest plots will cover the landscape.
Parker has done similar projects on a smaller scale, with 1 meter-squared plots. His findings back up the pros of diversity. Survival rates for saplings in mixed communities were only slightly higher than in segregated ones (3 percent), but those that lived grew 17 percent larger in a mix. A grasslands project at the University of Minnesota found the same thing: Plants grow better in mixed cultures than monocultures. The whole is greater than the sum of its parts.
Forests Past and Future
Project coordinator Whitney Hoot (left) helps Joseph Shirley plant a red maple. (Credit: Kristen Minogue/SERC)
When complete, the saplings will cover 60 acres of former cropland. There will be trees with special goo on their roots to help them absorb water. There will be trees with cages to protect them from deer. Some trees will even get a special “bloodmeal” spray of cow or pig blood, to see if the scent of a kill does a better job scaring off deer. All the while ecologists will track how the 75 mini-forests handle climate change, water pollution and animal communities.
Scientists aren’t the only ones with a stake in the forest. In Anne Arundel County, developers who cut down trees in critical area—land within 1,000 feet of shoreline—have to plant new trees inside the critical area or face a hefty fine. Their third option is to purchase forest mitigation credits. Since virtually all of BiodiversiTree falls within critical area, it can sell those credits in spades. It also can provide credits for animals, called forest interior dwelling species (FIDS) credits.
Phil Bishop, a SERC education volunteer who helped plant BiodiversiTREE. “I ran a computer center for years. Contracts. I said, when I quit, I’m going outside.” (Credit: Kristen Minogue/SERC)
But that is only the first half of the project. Nearby, another 70 acres of forest will remain untouched. As Parker and his successors watch the new forest grow beside it, they will face another question: What legacy does three decades of farming leave in its wake?
“It’s very stressful. I’ve never had a project this big,” Parker says. It isn’t just the immensity of this project on his mind. Parker still lives in the publish-or-perish world of all scholars. Having a century-long field experiment in place doesn’t change that. Still, most academics leave their legacies in journals. “When do you ever get a chance to leave something behind that’s not just words on paper?”
After they finish planting, Parker says he hopes to leave one more thing: A small open space on the edge of the woods with 16 trees, one of each species in the project. The trees will stand in two concentric rings, like Stongehenge. He wants to call it…”Treehenge.”
Posted in Publications | Comments Off on BiodiversiTREE: The Hundred-Year Forest Experiment
Artist’s depiction of the prehistoric synapsid Varanodon agilis (left) under attack from an ancient amphibian. (Wikimedia Commons/Smokeybjb)
Milk—the white, calcium-rich liquid common to mammals and refrigerators across the globe—may have evolved long before the mammals that secrete it. It may have evolved even before dinosaurs. It’s an idea SERC lactation expert Olav Oftedal proposed a decade ago and is now gaining momentum among biologists who study the evolution of what we drink.
Tom Mozdzer explores a patch of invasive Phragmites in SERC’s global change wetland.
Is it better to be a jack of all trades or a master of some? In the plant world, it’s possible to do both–and that could make a huge difference in deciding which plants dominate under climate change. This holds especially true for one: the invasive reed Phragmites australis. Its ability to alter its anatomy enables it to grow well in just about any environment, including one spiked with CO2 and nitrogen, SERC ecologists discovered in a study published Oct. 31.
Plants like this are called “jack-and-master” plants. Typically, the most competitive plants surpass their neighbors through one of two strategies. “Jack-of-all-trades” plants do moderately well under most scenarios. Their competitors will surpass them when conditions are good, but if the environment becomes stressful, the jack of all trades will grow better. “Master-of-some” plants do very well under only a few conditions, so if the environment shifts in their favor, they are certain to emerge victorious. But a few types—the jack-and-master plants—can use both tactics. And the invasive Phragmites is one of them.
