Photo right: Scientist Adam Langley sprays plants in a test chamber with nitrogen. The additional nutrients changed the composition of the plants inside the chamber, spurring the growth of grasses that respond weakly to elevated levels of CO2.

Plants build their tissue primarily with the CO2 they take up from the atmosphere. The more they get, the faster they tend to grow—a phenomenon known as the “CO2 fertilization effect.” However, plants that photosynthesize greater amounts of CO2 will also need higher doses of other key building blocks, especially nitrogen. The general consensus has been that if plants get more nitrogen, there will be a larger CO2 fertilization effect. Not necessarily so, says a new paper published in the July 1 issue of Nature.

Adam Langley and Pat Megonigal, two ecologists at the Smithsonian Environmental Research Center, conducted a four-year study on plants growing in a brackish Chesapeake Bay marsh. In 2006 they began feeding sedge-dominated plots a diet rich in CO2 and nitrogen. Just as atmospheric CO2 levels are rising, so is nitrogen pollution in estuaries due farming, wastewater treatment and other activities. Because the sedge has previously shown a large CO2 fertilization effect, Langley and Megonigal expected that adding nitrogen could only enhance it.

Photo left: The Smithsonian’s Global Change Research Marsh is a tidal system. It sits on the western shore of the Chesapeake Bay in Edgewater, Maryland.

The sedge, Schoenoplectus americanus, initially reacted as expected. However, after the first year something unanticipated happened. Two grass species that had been relatively rare in the plots, Spartina patens and Distichlis spicata, began to respond vigorously to the excess nitrogen. Eventually the grasses became much more abundant. Unlike sedges, grasses respond weakly to extra CO2 and do not grow faster. Thus, the nitrogen ultimately changed the composition of the ecosystem as well as its capacity to store carbon.
 
The experiment unfolded on the Smithsonian Global Change Research Wetland, located on the Chesapeake’s western shore in Maryland. The Smithsonian site has a history of climate change research that dates back to the 1980s. For this study, Megonigal and Langley placed 20 open-top chambers over random plots of plants. The chambers were 6 feet in diameter and had 5-foot-tall transparent plastic walls.

Photo right: Open-top plastic chambers allow Smithsonian researchers to control and measure the amount of carbon dioxide and nitrogen that the plants receive.

The large, plastic pods allowed the scientists to manipulate CO2 concentrations in the air and nitrogen levels in the soil. Half of the plots grew with normal, background CO2 levels; the other half were raised in an environment with CO2 concentrations roughly double that amount. Similarly, half of the chambers were fertilized with nitrogen and the other half were untreated.

 Langley and Megonigal began and ended each growing season with a census of the plants in each chamber. They noted the individual plant species, measured the above-ground biomass and the root growth. In the chambers that received the high-nitrogen diet, the plant composition changed dramatically; it went from 95 percent sedge in 2005 to roughly half grass in 2009. “It’s a fact that not all plants will be able to respond optimally to all changes,” said Megonigal. “The things they do respond to reflects their strategy for making a living in the environment.”

 “The study underscores the importance of considering the mix of species when you’re trying to predict how terrestrial ecosystems will react to global climate change factors,” said Langley. Rising CO2 levels will favor some plants and excess nitrogen will favor others. This lesson will be important to understand as scientists consider additional global change factors such as precipitation, temperature and, in tidal wetlands, sea-level rise. The plant species that gain a competitive edge under these evolving conditions will determine how ecosystems respond to global change.

 This study was supported by the U.S. Geological Survey and U.S. Department of Energy. The Smithsonian scientists recently received funding from the National Science Foundation that will sustain the research for another 10 years. Langley and Megonigal’s paper, “Ecosystem Response to Elevated CO2 Limited by
Nitrogen-Induced Plant Species Shift,” can be accessed on Nature’s website http://www.nature.com/nature/journal/v466/n7302/full/nature09176.html.

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 Photo right: Tintinnophagus acutus dinospore, with a flagellum.

Of the approximately 2,000 known species of living dinoflagellates, about 150 are parasitic. These organisms can alter the marine food web, in some cases destroying prey that consumers like copepods and larval fish rely upon. Coats first spotted T. acutus in the 1980s, in plankton samples he had collected from the Chesapeake Bay. Through his microscope, he noticed a ciliate being edged out of its lorica (shell) by a dinoflagellate. It looked different from others he had observed.

Describing a species is a serious undertaking. In the case of T. acutus, Coats and his collaborators documented its microscopic life cycle, conducted extensive DNA analysis and unearthed scientific papers dating back to 1873—when parasitic dinoflagellates were first noted by German scientist Ernst Haeckel.

Much of Coats’ work involved understanding, questioning and clarifying various accounts of similar dinoflagellates that have been written over the years. He read studies published in French, German and English. This thorough research resulted in more than the introduction of T. acutus: it provided new understanding of the evolutionary relationships among parasitic dinoflagellates and it better defined their position within the dinoflagellate lineage of the tree of life.

Photo left: The host lorica (shell) contains the host ciliate Tintinnopsis cylindrica (upper part), which is being consumed by the parasitic dinoflagellate Tintinnophagus acutus (bottom, yellow). (Wayne Coats photos)

Protist phylogeny has never been Coats’ primary focus. T. acutus is the second species that he has named and described. This fall Coats will retire from SERC; he says he expects to have time to describe a few more species of parasitic dinoflagellates. –Tina Tennessen

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View Muddy Creek and the Rhode River in a larger map

To survey the animals swimming up and down Muddy Creek, researchers use a fish weir—an expanse of nets, gates and boardwalks—that temporarily blocks aquatic traffic. Once a week, the researchers close the weir, set out the nets and identify and count all the species that get trapped. They began collecting data in 1983.

This type of fine-scale surveying, done on a weekly basis, is rare. It’s even more unique to have such long-term data. Many ecological studies are funded for just a few years at a time. These short time frames make it difficult for scientists to observe changes and patterns in species populations and composition.

In honor of the 2010 U.S. Census, staff at the Smithsonian Environmental Research Center have created this slide show of a recent spring survey. The salinity on this April day was fairly low and nearly a dozen golden shiners (a freshwater minnow) were caught along with several estuarine-resident and a few diadromous (fish that migrate between fresh and saltwater) species. Among the highlights: a sizeable snapping turtle, many white perch in spawning condition, juvenile American eels and a parasite.

Human activity and environmental conditions can affect which species are swimming in Muddy Creek. The water is brackish and salinity levels change seasonally and from year to year. During winter and early spring, when freshwater flow is usually the highest, researchers will generally catch more freshwater species like bluespotted and banded sunfish–-two protected species in Maryland. During periods of high salinity, researchers can catch many species indicative of the higher saline lower Bay such as red drum, spotted sea trout and Spanish mackerel. –Tina Tennessen

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The study, conducted by Geoffrey Parker, a forest ecologist at the Smithsonian Environmental Research Center in Edgewater, Md., and Sean McMahon, a postdoctoral fellow at the Smithsonian Tropical Research Institute, utilizes data collected for more than 20 years by Parker from stands of mixed hardwood forest plots in Maryland. Data has revealed that the forests are adding an additional 2 tons per acre annually.

Photo left: Smithsonian forest ecologist Geoffrey Parker began his tree censuses his first day on the job, Sept. 8, 1987. Here he measures a tree on the grounds of the Smithsonian Environmental Research Center. (Photo by Kirsten Bauer)

Forests and their soils store the majority of the Earth’s terrestrial carbon. Small changes in the growth rate of the forest scientists believe, can have a significant impact on weather patterns, nutrient cycles, climate change and biodiversity.

In forest plots at SERC, Parker has meticulously tracked the growth of trees 5 to 225 years old. Data show that more than 90% of the stands grew two to four times faster than predicted from the baseline data.

By grouping the forest stands by age, McMahon and Parker were also able to determine that the faster growth is a recent phenomenon. If the forest stands under study had been growing this quickly their entire lives, the stands would be much larger than they presently are.

Photo right: Jess Parker, his colleagues and a team of citizen scientists have tagged more than 20,000 trees at the Smithsonian Environmental Research Center. These metal bands expand as the diameter of the tree increases, recording its growth. (Photo by Kirsten Bauer)

Parker began his tree census work Sept. 8, 1987—his first day on the job at the Smithsonian. He recorded and tracked trees 2 centimeters or more in diameter, identifing them to species and marking each tree’s exact coordinates on a map.

By knowing its species and diameter, McMahon, who specializes in data-analysis and forest ecology, is able to calculate the biomass of a tree. “Walking in the woods helps, but so does looking at the numbers,” he says.

“We made a list of reasons these forests could be growing faster and then ruled half of them out,” Parker says. The reasons that remained included increased temperature, a longer growing season and increased levels of atmospheric CO2.

Photo right: The tulip poplar, shown here, is a common tree in the temperate forests surrounding the Smithsonian Environmental Research Center.  Other species include sweetgum, American beech, and southern red oak. (Photo by Kirsten Bauer)

During the past 22 years CO2 levels at SERC have risen 12%, the mean temperature has increased by nearly three-tenths of a degree and the growing season has lengthened by 7.8 days. The trees now have more CO2 and an extra week to put on weight. Parker and McMahon suggest that a combination of these factors has caused the forest’s accelerated biomass gain.

The findings are also important for policymakers trying to address climate change. Future carbon cap-and-trade rules will need to quantify the amount of carbon forests hold. If faster growth rates prove the norm, this could affect the formulas and the dollar value assigned to forests that are cut or conserved.

Parker and McMahon don’t expect SERC’s forest to continue growing at this accelerated rate forever. Some day the growth rate will level off. When that happens, they wonder how that will affect carbon dioxide levels. If trees are sponges that absorb CO2, what will happen to CO2 levels in our atmosphere when the trees become saturated? It’s a question for further exploration. In the meantime, Parker will continue walking through the SERC woods, tape measure in hand, carefully tracking the growth of the trees.  –Tina Tennessen

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Photo: Downtown Annapolis and Spa Creek, leading into the Severn River and Chesapeake Bay. (Photo by Jane Thomas)

Using forecasts of atmospheric carbon dioxide production for the coming century, the scientists predict the water of the Bay will see rising levels of dissolved carbon dioxide and higher water temperatures. As a result, climate change is expected to worsen problems of low dissolved oxygen concentrations in the Chesapeake’s water and cause sea levels to rise.

For fish and other organisms living in the Bay, the scientists predict:  

• Populations of marine fish that favor warmer water and whose northern range ends near the Chesapeake can be expected to increase.  These include southern flounder, cobia, Spanish mackerel, mullet, tarpon, black drum, red drum, spotted sea trout, spot and Southern kingfish.
• Many fish species that favor cold water will disappear or become less abundant in the Chesapeake Bay, including soft clams, yellow perch, white perch, striped bass, black sea bass, tautog, summer and winter flounder and scup;
• Fish susceptible to winter die-offs due to the seasonal cold weather of the Chesapeake may see a strengthening of their populations due to warmer water, with more juveniles surviving through the winter.
• Warmer water also may result in longer growing seasons for fish, resulting in increased yield by some commercial fisheries. Lack of surface freezing in shoreline habitats could improve opportunities for oysters and other intertidal species to colonize shorelines.
• Some fish parasites also will likely benefit from warmer water, increasing their impact on fish and oysters in the bay.
• Rising sea levels will submerge some of the Bay’s wetlands, which many ecologically and economically important fish use as nursery areas and as foraging grounds. Degradation of these habitats could affect the larger ecosystem of the Northeast U.S. continental shelf, as many of these species spend their lives in the coastal Atlantic.
• An increase of carbon dioxide in the water of the Chesapeake may raise the acidity of the Bay and gradually reduce the ability of oysters, clams, mussels and other animals to build calcium carbonate shells.

Photo: Chesapeake Bay oysters on sale at a fish market in Washington, D.C.

With warming temperatures, “the species that make up the food web of the Chesapeake Bay will be impacted differently, likely disrupting the normal predator prey interactions between these animals,” says Denise Breitburg, a scientist at the Smithsonian Environmental Research Center in Edgewater, Md.  Hypoxia, or a lack of oxygen in the water, will be one prevailing characteristic of warmer Bay water, Breitburg predicts. “At warmer temperatures microbes will consume oxygen at a higher rate and less oxygen can dissolve in warm water. At the same time fish and perhaps other animals, will require more oxygen in warmer water.” With these factors in mind, “we would expect more severe episodes and negative effects of low oxygen in the Chesapeake,” Breitburg says.

The scientific paper “Potential climate-change impacts on the Chesapeake Bay,” is available at the Web address:  http://snurl.com/talub

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Invasive species, contaminants, excessive nutrient’s and sediment are just some of the many factors threatening sensitive wetlands and seagrass beds. An additional issue has been community efforts to “harden” shorelines by lining shores with bulkhead, rock or rubble to try to protect adjoining lands against erosion and sea level rise. These structures can threaten the health of living shorelines, such as wetlands and marshes. This project will look at the combined effects of these multiple stresses on nearshore habitats and their dependent species.

Image: A satellite view of the Chesapeake Bay.

“These habitats which are nursery and feeding grounds for so many species, have typically been managed in a piecemeal, parcel-by-parcel fashion and are slipping away in areas of heavy development,” said Robert Magnien, director of the NOAA National Centers for Coastal Ocean Science’s Center for Sponsored Coastal Ocean Research, which awarded the grant. “Developing scientific information that ties multiple species and their environment will be used to advance management approaches.”

The Smithsonian Environmental Research Center leads the nation in research on linkages of land and water ecosystems in the coastal zone and provides society with knowledge to meet critical environmental challenges in the 21st century.

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The Smithsonian Center for Education and Museum Studies is hosting “Climate Change,” a three-day, free, education online conference Tuesday, Sept. 29 through Thursday, Oct. 1. This is the second in a series of Center for Educatin and Museum Studies conferences where researchers and curators from around the Smithsonian Institution come together to address a single subject.

“Climate Change” will feature sessions everyone will find thought provoking and relevant. Some sessions will be of special interest to educators while others will engage entire classrooms and the general public. Throughout the conference, participants will explore Smithsonian research and collections related to the evidence, impact and response to climate change. Alongside Smithsonian scientists and curators, the public will examine the issues surrounding climate change from the perspectives of science, history and art.

Photo: Scott Wing has used ginko fossils like this to estimate the amount of carbon dioxide in the atmosphere during the Eocene. (James DiLoreto)

“We’re excited to offer this online seminar on such an important and timely topic as climate change. The Smithsonian, with its experts, collections and partners is uniquely qualified to do so,” Wayne Clough, Secretary of the Smithsonian, says. “Our first seminar, on Abraham Lincoln, was a resounding success that started an online dialogue that continues today—here and abroad.”  Presenters include:

*Bert Drake, senior scientist at the Smithsonian Environmental Research Center, who leads two major studies of the impact of atmospheric carbon dioxide on ecosystems;

 *Don Moore, associate director for animal care at the Smithsonian’s National Zoological Park, who helps create conservation-management plans for wildlife; and

*Scott Wing, paleontologist at the Smithsonian’s National Museum of Natural History, who specializes in prehistoric plant life and its reactions to climate change.

 The conference will show the depth of research that the Smithsonian is conducting on climate change. Smithsonian scientists and other experts will lead participants in explorations of Smithsonian research on this important issue via live presentations, moderated forums and demonstrations. Through live streaming, speakers will respond to questions and comments from the audience. All of the conference sessions will be recorded and archived and can be replayed at any time via the Web at www.SmithsonianEducation.org.

Registration is open to everyone at www.SmithsonianEducation.org/Climate.

This site also features a blog about climate change and an archive of the first online conference, “Abraham Lincoln,” which attracted more than 3,000 participants on six continents.

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