by Kristen Minogue
Arctic sea ice (Patrick Kelley/U.S. Coast Guard)
For the first time in roughly 2 million years, melting Arctic sea ice is connecting the north Pacific and north Atlantic oceans. The new sea routes leave both coasts and Arctic waters vulnerable to a large wave of invasive species—a problem the Arctic has largely avoided until now.
by Kristen Minogue
A flounder in a bed of eelgrass. Seagrasses and other underwater plants provide food and shelter to many iconic Bay creatures, including blue crabs. (NOAA)
It’s been a difficult century for the submerged flora of Chesapeake Bay.
In the 1930s, wasting disease nearly wiped out the eelgrasses of the North Atlantic. In the ‘50s and ‘60s, they faced onslaughts from invasive grasses like water chestnut and Eurasian milfoil. Finally, in the summer of 1972, Hurricane Agnes pummeled underwater plants to the lowest levels ever reported in the Bay. This April, they received news that, at first glance, seemed positive: Submerged grasses rose 24 percent between 2012 and 2013, according to aerial surveys of the Chesapeake Bay Program.
But those increases were largely limited to a single species: widgeon grass, a plant known for wild fluctuations. At 60,000 acres total, submerged plants still didn’t come near a recent mini-peak in 2002, they’re a far cry from the ultimate goal of 185,000 acres across the Bay. What is holding them back? And—more importantly—how we can we help ensure the latest expansion isn’t just a blip?
by Kristen Minogue
An open pit exposes a 3200-year-old shell midden. Native Americans used middens as trash piles for oyster shells, animal bones and pottery. (Torben Rick/Smithsonian)
More than 3,000 years ago, Native Americans dined on shellfish from the Chesapeake Bay, and the leftovers from those feasts are still benefiting modern-day forests.
Native Americans inhabited the Chesapeake Bay area more than 13,000 years before the first Europeans dropped anchor. During the Woodland period (3,200 to 400 years ago), they ate eastern oysters and threw the shells, along with animal bones, pottery and other shellfish remains, into trash piles called shell middens. Those piles enriched the soil with nutrients, promoting hot spots of native diversity along the Chesapeake shoreline.
by Kristen Minogue and John Parker
White-tailed deer. (John Parker/SERC)
In deer-populated forests, tastier plants can avoid being eaten if they are surrounded by less appealing plants. But with deer gone, diverse plots become weaker and plants are better off sticking to their own kind.
Scientists uncover milk composition of naked mole-rat queens
by Micaela Jemison
Naked mole rats at the National Zoo (Meghan Murphy)
Naked mole-rats live their lives entirely underground in Africa, digging tunnels in a perpetual search for plant tubers to eat. These bizarre creatures are unlike nearly every other mammal on earth in that the burdens of reproduction and milk feeding of young are placed solely on a single queen and are not shared among the females of the colony.
While this system may work well for insects like bees where the young are fed by a horde of workers and nurses, scientists were perplexed as to how this system works for a mammal where one mother must produce milk for her very large brood.
by Kristen Minogue and Heather Dewar
SERC ecologist Kyle Cavanaugh explores a field of white mangroves. (SERC)
As mangrove trees lose ground to deforestation and urban sprawl, one development seems to be giving them a boost: climate change. Fewer winter cold snaps have empowered them to conquer new territory around their northern Florida boundary, according to a study of 28 years of satellite data from the Smithsonian Environmental Research Center and the University of Maryland.
An estimated 35 percent of the world’s mangroves have been destroyed since 1980, according to previous research, outstripping tropical rainforests and coral reefs. They are also some of the planet’s most valuable ecosystems. Mangroves protect coastal cities from floods and hurricanes. Their above-ground roots shelter many commercially valuable fisheries, including blue crabs, shrimp and lobsters. And they are phenomenal at burying carbon. The soils of coastal ecosystems like mangroves can store carbon at a rate 50 times higher than tropical rainforests. Scientists have estimated their total ecosystem services value more than $1.6 trillion a year—making the expansion a possible blessing.
“Some people may say this is a good thing, because of the tremendous threats that mangroves face,” said the study’s lead author, Kyle Cavanaugh, a postdoctoral research fellow at the Smithsonian Environmental Research Center in Edgewater, Md. “But this is not taking place in a vacuum. The mangroves are replacing salt marshes, which have important ecosystem functions and food webs of their own.”
by Kristen Minogue
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.
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)
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.
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.
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.
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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