New study shows hardened shorelines may mean fewer fish and crustaceans.
by Ryan Greene
A new SERC study shows that both bulkheads (left) and riprap revetment (right) are associated with lower abundance of several species of fish and crustaceans in the Chesapeake Bay and the Delaware Coastal Bays. Credit: SERC
For decades, ecologists have suspected that hardened shorelines may impact the abundance fish, crabs, and other aquatic life. But now they have evidence that local effects of shoreline hardening add up to affect entire ecosystems. A new study by scientists at the Smithsonian Environmental Research Center (SERC) shows that more shoreline hardening means fewer fish and crustaceans in our waters.
Given the predictions for the coming years (i.e. rising seas and more of us living on the coast), this finding is a cause for concern. Many people will likely try to protect their land from flooding and erosion by armoring their shorelines with vertical retaining walls (bulkheads) or large rocks (riprap revetment). But as SERC researchers found in their new paper, published in Estuaries and Coasts, the impact of these hardened shorelines adds up.
Lead author and former SERC postdoc Matt Kornis likens shoreline hardening to littering. While each individual bit of trash isn’t a huge problem, the combined effect can be enormous. Kornis, now a biologist for the U.S. Fish & Wildlife Service, says the same is true of shoreline hardening. Each individual bulkhead or riprap revetment may not be catastrophic, but cumulatively they can contribute to shrunken populations of ecologically—and economically—important species like the blue crab.
“Shoreline hardening can cause loss of habitats important for young fish, like wetlands and submerged vegetation,” Kornis says. “That may be one reason we observed low abundance of many species in estuaries with a high proportion of hardened shoreline.” Click to continue »
That’s why Uzay Sezen carries a crossbow and liquid nitrogen into the forest with him.
by Ryan Greene
Intern Alex Koure (left) and postdoctoral researcher Uzay Sezen (right) are using a crossbow to get leaf samples from hard-to-reach branches. A fishing line attached to the arrows helps them shake down leaves from the canopy. Credit: Ryan Greene/SERC
Uzay Sezen with his crossbow and liquid nitrogen in Harvard Forest. Credit: SERC
With senior scientist Sean McMahon and other members of the Quantitative Ecology Lab, Sezen is embarking on a multiyear study which aims to unveil the genetic patterns of tree growth. Their mission: Find out if tree species present at both SERC and Harvard Forest grow in the same way, and whether there are particular genes they express when they grow. Not only will this help us understand how trees respond to day-to-day changes in sunshine, temperature, and rainfall, but it may provide insight into how forests will react (and already are reacting) to global factors like climate change.
Since about 2009, scientists at SERC have been using metal bands called dendrometersto measure how trees grow (within a hundredth of millimeter!) over years, seasons, weeks, and even days. According to SERC technician Jessica Shue, combining these physical measurements with Sezen’s genetic analysis may help reveal what makes some trees in the forest winners and others losers.
“Now that we can look at the genetics, we can look at a much finer scale at what’s causing some trees to be dominant in the canopy, and others of the same species [to be] stuck in the understory,” she says.
How, though, do you ask a tree which genes it’s using?
A stand of mangrove trees in Florida (Credit: Yinan Chen under CC0/Public Domain license)
With their tall, arching roots reaching down like hands into the water, mangrove trees can look downright creepy. And yet they’re critical species for the environment—and humans—on five different continents: They can create their own islands, provide one-of-a-kind habitats for wetland creatures, and store carbon like mad. They also protect shorelines from storms and tsunamis. Unfortunately, and perhaps unsurprisingly, humans are destroying them at a rate that may doom them within a century.
Aquaculture, urban development, tourism, and agriculture are threatening mangrove habitats around the world. Like many natural ecosystems, they are being cut down and destroyed to make way for human endeavors, and human pollution is taking its toll on their growth at the same time. But even as their total acreage decreases, they’re gaining ground in some places. Climate change is causing mangroves to move beyond their tropical habitats and take over neighboring salt marshes, but not always predictably. In North America and South Africa, they are moving toward the poles, while in Australia they are expanding along an east-west axis. All these disappearances and migrations present a riddle for scientists—but one they will need to solve to prevent habitat loss and prepare for a warmer future. Click to continue »
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Kim Komatsu in Konza Prairie, Kansas, home to one of the first Long-Term Ecological Research (LTER) programs. (Credit: Arjun Potter)
Kim Komatsu does big-picture ecology. The newest senior scientist at the Smithsonian Environmental Research Center, Komatsu is leading the center’s Ecosystem Conservation Lab. But while working on large-scale global experiments, she also delves into the microscopic world of bacteria. In this Q&A, discover how bacteria give certain plants an edge, and how she blends the very large and the very small.
This is the first of three profiles about the young scientists heading SERC’s newest labs. Edited for brevity and clarity.
You’ve done a great deal of work with legumes—plants in the bean and pea family. Can you talk about their weird relationship with rhizobial bacteria?
The [legume] plants and bacteria are in a mutualism where the plants fix carbon into sugar and give it to the bacteria, and the bacteria are able to take nitrogen from the atmosphere and give it to the plants. This is a source of nitrogen that no other plants have access to. Most plants have to take [nitrogen] up from the soil. Because of this mutualism, legumes can get nitrogen from another source, and that often makes them very successful in different, especially harsh environments….
It’s interesting to think about the different legume species, and how good they are at enforcing cooperation from the bacteria. Thinking about the bacteria as not only potentially being beneficial, but [also possibly] cheating the system—trying to take carbon from the plants and not give back as much nitrogen, especially under high soil nitrogen conditions. Click to continue »
Fishing, camping, and walking the dog can all have unintended consequences. (Credit: pixabay.com, 1,2,3. Used under Creative Commons CC0 license)
By Joe Dawson
Nothing seems to draw people outside like a beautiful summer weekend. A rain-free Saturday could mean taking the boat out on the water for some fishing or a family camping trip. Conservationists have found, however, that many summer activities carry the risk of spreading invasive species. A species gets the name “invasive” if it is not native to a location and causes environmental and economic damage. Here are five popular activities that can spread invaders–and tips for enjoying them safely: Click to continue »
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Zebra mussels in the Great Lakes, lionfish in the Atlantic and pythons in the Everglades: Large creatures like these generally draw the spotlight when talking about ways to combat invasive species. But for every visible invader, there are hundreds more too minuscule to see with the naked eye. These species often slip in unnoticed—and unregulated—in the ballast water of large ships.
Dennis Whigham samples horsetail plants in an Alaskan headwater stream. Credit: Ryan King/Baylor University
In Alaska, fish mean serious money. For fishermen, landowners, and the government, learning all they can about the lives of salmon could pay off in future fish harvests. There’s a lot to learn, down to how a single type of tree impacts their habitat.
The story of those habitats and trees, the alders, has been explored by SERC senior scientist Dennis Whigham and colleagues in a new study published May in Science of the Total Environment. The researchers have been studying interactions between watersheds and headwater streams for almost two decades.
Alders are most recognizable for their egg-shaped, serrated leaves. Their bark is used for tanning leather, and their wood to smoke salmon and make Fender guitars. But alders also have an outsized effect on their natural environment, transforming the chemistry and structure of wetlands and streams nearby. Bacteria in alder roots make nitrogen, an important plant nutrient, available in places where it is otherwise scarce. This can send ripple effects through entire ecosystems. In another plot twist, scientists also expect alder trees to expand northward, stirred by warmer temperatures and higher carbon dioxide from climate change. Whigham’s findings highlight the interconnectedness of wetland ecosystems, waterways, and the valuable fish that call Alaska home. Click to continue »
Methane flux chambers keep track of how much methane a tree trunk releases or consumes. Credit: Pat Megonigal/SERC
Rainbow-colored tubes snake through the undergrowth. White acrylic chambers sit mounted to tree trunks like giant bleached snails. At first glance, it’s not quite clear what the heck is going on. Cryptic as it may seem, these tubes and chambers are the key to a recent study showing that trees in upland forests are capable of emitting the planet-warming greenhouse gas, methane.
Scientists have long considered upland forests to be methane sinks due to the presence of methane-hungry microbes called methanotrophs in their soils. But new research by Pat Megonigal, an ecosystem ecologist who heads up the Biogeochemistry Lab at the Smithsonian Environmental Research Center (SERC), and Scott Pitz, a graduate student from Johns Hopkins, has shown that when it comes to upland forest methane cycling, soil isn’t the only game in town. Trees and their emissions are part of the equation too.
In a recently published study in New Phytologist, Megonigal and Pitz found that trees in upland forests are actually capable of emitting methane through their trunks. This means that some of the methane absorbed by methanotrophs in the forest soils may be offset by tree emissions.
Why, though, does any of this even matter?
When researchers think about global climate change, they need to think about heat-trapping greenhouse gases like carbon dioxide (CO2) and methane (CH4). Specifically, they’ve got to track these gases to see where they’re coming from (their sources) and where they’re getting stored (their sinks). Carbon dioxide receives much of the spotlight (and rightfully so, given its enormous impact on the global climate), but it’s also critical to keep an eye on methane. Although methane stays in the atmosphere for far less time than carbon dioxide, it’s capable of trapping up to 45 times more heat. In other words, methane is a big deal. If temperate forests are consuming less of it than we thought, as Megonigal and Pitz’s research suggests, that could be a big deal too. Click to continue »
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SERC citizen scientist Dave Norman stands beside a collection of sediment samples from the bottom of Chesapeake Bay. (Sara Richmond)
Dave Norman’s first visit to the Smithsonian Environmental Research Center (SERC) wasn’t to help with a field trip or assist researchers in the crab lab, as he has done for the past two years. In fact, he knew very little about SERC, but was competing in a triathlon on its campus. The experience stuck with him, and when he retired a year later, he contacted SERC to ask how he could get involved as a volunteer.
The volunteer program offered a mix of science and education opportunities that turned out to be a perfect fit for Dave. He says he was part of the “Jacques Cousteau generation,” who grew up with the explorer’s books and movies, and eventually started college with plans to become a marine biologist. Those plans changed—he would practice law for 30 years before becoming a seventh-grade math teacher—but when he retired, his love of the water brought him back to the field. Click to continue »
Strategy To Flush Invaders From Ballast Water Coming Up Short
by Kristen Minogue
SERC marine biologist Jenny Carney descends the gangway of a giant bulker ship in Virginia. When ships export coal and other goods, they return loaded with ballast water from foreign ports—and often inadvertently bring invasive species with them. (Credit: Kim Holzer/SERC)
In the battle against invasive species, giant commercial ships are fighting on the front lines. But even when they follow the rules, one of their best weapons is coming up short, marine biologists from the Smithsonian Environmental Research Center (SERC) discovered in a new study published in PLOS ONE Monday.
As ships move goods around the world, they often inadvertently ferry invasive species as well. These new species can come over in the ships’ ballast water—the water ships pump on board for stability, to keep them from becoming top-heavy. But when the ships arrive to port, they often discharge their ballast water from distant global regions, along with the unseen, unwanted hitchhikers.
Shipping companies and biologists have known about this problem for decades and are still struggling to combat it. Currently, their main strategy is called “open-ocean exchange.” The idea is to flush out ballast water from their original port in the open ocean, to remove most coastal organisms, and replace it with water more than 200 nautical miles from shore. When they arrive at their destinations and discharge their new ballast water, any open-ocean organisms they picked up are unlikely to survive in ports and coastal waters.
“Ballast-water exchange provides a stop-gap measure until new technologies can be implemented to further reduce species transfers,” said Greg Ruiz, SERC senior marine biologist and a co-author of the new study. Since 2004, the U.S. Coast Guard has required most commercial ships entering the U.S. from overseas to do open-ocean exchange before discharging ballast in ports. However, this strategy has some serious limitations and may not be as effective as scientists and policymakers once hoped. Click to continue »
Posted in Invasive Species, Publications | Comments Off on Ships Struggle To Battle Invasive Species As Global Trade Surges
