Freshwater mussels discovered in urban Delaware river

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Scientists working with the Partnership for the Delaware Estuary and The Academy of Natural Sciences have made an important discovery in the Delaware River between Chester, Pennsylvania, and Trenton, New Jersey: beds of freshwater mussels. This includes several uncommon species, two of which were previously believed to no longer exist in both Pennsylvania and New Jersey. “Freshwater mussels are very sensitive to a variety of problems, including pollution, dams, water flows, loss of forests, and harvesting for their shells and as bait,” said Dr. Danielle Kreeger, science director at the Partnership for the Delaware Estuary. “We have so few mussels left in almost all of our streams in the area, so to find seven species living together in dense communities right near Philadelphia was unexpected and cause for celebration.”

Freshwater mussels are the most imperiled of all plants and animals in North America Nearly three-quarters of the continent’s 300 species are in decline, and many are either extinct or headed toward extinction. In the Delaware River Basin, most of the one dozen native species are classified as reduced, threatened, or locally extinct. One of the basin’s species is considered endangered at the federal level and others are listed as endangered at the state level. Water pollution and degraded habitats are the most common reasons for these declines. That is why scientists are so excited to find them in this stretch of the river.

One reason freshwater mussels may be doing better in the Delaware River compared to surrounding tributaries is the fact that the Delaware is the longest free-flowing river east of the Mississippi. Dams often block fish from swimming up the river, and this can interrupt the complicated breeding processes of freshwater mussels. Mussels rely upon fish to carry their babies, or larvae, around, including upstream. Whenever dams block these fish, they fail to deliver their payload of mussel larvae to new areas where they can grow and thrive. Pennsylvania has more dams than any other state, and many of these are located in streams throughout the Delaware Valley. The lone exception is the Delaware River.

“Until this discovery, our surveys for freshwater mussels in southeastern Pennsylvania during the past 10 years have painted a grim picture. Only one species seems to still be prevalent in the area’s streams, and even that species is found in only a handful of locations anymore,” said Roger Thomas, staff scientist at the Academy of Natural Sciences’ Patrick Center for Environmental Research in Philadelphia. These recently discovered beds of mussels can be used to help support mussel reintroduction into other areas where they have been lost.”

Dr. Kreeger and others are in the process of expanding a fledgling mussel-restoration effort with support from a number of funders. These include ConocoPhillips, the National Fish and Wildlife Foundation, and the Pennsylvania Coastal Resources Management Program. She believes it is now possible to increase mussel populations throughout the Delaware River Basin by either breeding them in a hatchery or relocating adults during breeding season by releasing them in targeted streams. She and her colleagues at the Academy of Natural Sciences have been working with Cheyney University, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey to experiment with different methods since 2007. They call their effort the Freshwater Mussel Recovery Program.

The Partnership for the Delaware Estuary is restoring mussels for many reasons, not just the fact that these animals are rare and endangered.

“Dense beds of mussels filter pollutants and make conditions better for fish and other aquatic life, improving water quality downstream in the estuary,” said Jennifer Adkins, executive director of the Partnership for the Delaware Estuary. “We may have these beds of mussels to thank for keeping certain types of pollution, like nutrients, low in this part of the river. This helps make our waters more inviting for everyone.”

Restoring freshwater mussels won’t be easy or fast, however. Although freshwater mussels can help to boost water quality, they are also some of the most sensitive animals to polluted water. Therefore, some area streams may not be able to sustain mussels until water quality is further improved or riverside woodlands are replanted. Also, freshwater mussels live to be up to 100 years old and are slow growing. But this does not concern Dr. Kreeger, who said, “We’ve made tremendous strides in improving some environmental conditions needed to support healthy ecosystems. That said, we know our job won’t be complete until we see the return of these long-lived sentinels of healthy waterways.”

Water resources played important role in patterns of human settlement, new UNH research shows

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Once lost in the mists of time, the colonial hydrology of the northeastern United States has been reconstructed by a team of geoscientists, biological scientists and social scientists, including University of New Hampshire Ph.D. candidate Christopher Pastore. The results, which extend as far back as the year 1600, appear in the current issue of the journal Environmental Science & Technology in the article “Tapping Environmental History to Recreate America’s Colonial Hydrology.” The findings provide a new way of uncovering the hydrology of the past and will lead to a better understanding of hydrologic systems now and in the future, the scientists say.

“We outline a methodology for synthesizing modern scientific data with historical records, including anecdotal sources,” Pastore says, the paper’s lead author. “It underscores the role of humans in an assessment of hydrologic change.”

Throughout American history, water resources have played an integral role in shaping patterns of human settlement and networks of biological and economic exchange.

“The research emphasizes the effect of human activities on the evolution of watersheds and on the dynamics of ecosystems, important to water sustainability,” says Thomas Torgersen, program director in National Science Foundation’s Division of Earth Sciences, which funded the research.

The scientists divided their study area into three geographic and socio-political subregions: New England; the Middle Colonies; and the Chesapeake. They then looked at the ways in which physical variables–such as soil, vegetation, and climate–combined with socio-political factors to influence each subregion’s hydrologic environment.

In New England, for example, close-knit religious communities with strong central governments concentrated their economic efforts on fur-trading and timber extraction, according to the paper’s co-authors, which include Charles Vörösmarty of the City University of New York, principal investigator on the NSF grant. Vörösmarty is formerly the director of the Water Systems Analysis Group at the UNH Institute for the Study of Earth, Oceans, and Space.

The Chesapeake region, on the other hand, was settled largely by young, unskilled men who cleared trees and planted tobacco fencerow to fencerow. “This caused extensive erosion, which dramatically altered rivers,” Pastore says.

The Middle Colonies were characterized by diverse social, cultural, and religious traditions and feudal-style estate agriculture.

Integration of human decision-making into analyses of land-cover change, engineering and climate change is fundamental to understanding subregional hydrologic patterns and how they interact, the scientists say.

They recommend two metrics for quantifying hydrologic change.

The first, which they call a simple water balance, takes into account precipitation, evapotranspiration, and water storage, which can be used to track changes in annual river discharge. The second, termed mean water residence time, or the average time a water molecule spends in one place, can also be used to calculate the amount of water moving through a system.

The resulting information helps determine past water residence times, which in turn allow scientists to infer changes in the biogeochemistry of rivers and streams.

Many pathogens, or disease-causing organisms, are linked to water flows. An understanding of historical water residence times, says Pastore, may lead to new insights into how diseases are transmitted today.

Biofuels production has unintended consequences on water quality and quantity in Mississippi

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Growing corn for biofuels production is having unintended effects on water quality and quantity in northwestern Mississippi. More water is required to produce corn than to produce cotton in the Mississippi Delta requiring increased withdrawals of groundwater from the Mississippi River Valley alluvial (MRVA) aquifer for irrigation. This is contributing to already declining water levels in the aquifer. In addition, increased use of nitrogen fertilizer for corn in comparison to cotton could contribute to low dissolved oxygen conditions in the Gulf of Mexico.

These are some of the key findings from a study conducted by the U.S. Geological Survey (USGS) to assess water quality and quantity in the Mississippi Delta, in relationship to biofuels production.

“Because corn uses 80 percent more water for irrigation than cotton, exchanging corn for cotton will decrease water-levels,” according to Heather Welch, USGS Hydrologist and author of this USGS Report. Declining water levels in the MRVA aquifer are particularly significant in the Mississippi Delta, where the infiltration of rainfall to replenish the aquifer is low. “This is a low flat area. When it does rain, much of the precipitation is lost through evapotranspiration and to streamflow, so the rainwater never reaches the aquifer,” explains Welch.

In 2006, the U.S. Department of Energy Biomass Program implemented the Biofuels Initiative. The initiative calls for the replacement of 30 percent of gasoline levels by ethanol by 2030 and the reduction of ethanol costs to prices competitive with gasoline by 2012. In the Mississippi Delta, implementation of this initiative resulted in a 47-percent decrease in the number of acres dedicated to producing cotton, which resulted in a corresponding 288-percent increase in corn acreage in the region from 2006 to 2007.

Using the USGS SPARROW model (SPAtially Referenced Regression on Watershed), scientists found that the conversion of cotton to corn acreage (comparing 2007 to 2002) is estimated to have increased the nitrogen load for the Yazoo River by 7 percent. The Yazoo River Basin has been identified as a contributor of nitrogen to the Gulf of Mexico. Levels of nitrogen in the Gulf of Mexico have resulted in low dissolved oxygen conditions which can impact fish and bottom dwelling organisms.

Locally, water level declines and decreasing water quality contributes to the Delta’s poor ecosystem health. “We are seeing a loss of habitat complexity, and lowered water levels have decreased baseflow to streams,” says Jeannie Barlow, USGS Hydrologist and co-author of the study. “Some streams have remained dry for months in the summer and fall during periods of low rainfall,” says Barlow.

According to data provided by the Yazoo Mississippi Delta Joint Water Management District (YMD), the total amount of water stored in the aquifer has declined since 1980, and current withdrawals from the aquifer are greater than the amount of water entering the aquifer.

These USGS findings provide essential scientific information about the effects of corn-based ethanol on water resources that Delta producers can use when making their planting decisions.

Venus holds warning for Earth

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Venus holds warning

Venus holds warning

A mysterious high-altitude layer of sulphur dioxide discovered by ESA’s Venus Express has been explained. As well as telling us more about Venus, it could be a warning against injecting our atmosphere with sulphur droplets to mitigate climate change. Venus is blanketed in sulphuric acid clouds that block our view of the surface. The clouds form at altitudes of 50 km when sulphur dioxide from volcanoes combines with water vapour to make sulphuric acid droplets. Any remaining sulphur dioxide should be destroyed rapidly by the intense solar radiation above 70 km.

So the detection of a sulphur dioxide layer at 90� km by ESA’s Venus Express orbiter in 2008 posed a complete mystery. Where did that sulphur dioxide come from?

Now, computer simulations by Xi Zhang, California Institute of Technology, USA, and colleagues from America, France and Taiwan show that some sulphuric acid droplets may evaporate at high altitude, freeing gaseous sulphuric acid that is then broken apart by sunlight, releasing sulphur dioxide gas.

“We had not expected the high-altitude sulphur layer, but now we can explain our measurements,” says Håkan Svedhem, ESA’s Venus Express Project Scientist.

“However, the new findings also mean that the atmospheric sulphur cycle is more complicated than we thought.”

As well as adding to our knowledge of Venus, this new understanding may be warning us that proposed ways of mitigating climate change on Earth may not be as effective as originally thought.

Nobel prize winner Paul Crutzen has recently advocated injecting artificially large quantities of sulphur dioxide into Earth’s atmosphere at around 20 km to counteract the global warming resulting from increased greenhouse gases.

The proposal stems from observations of powerful volcanic eruptions, in particular the 1991 eruption of Mount Pinatubo in the Philippines that shot sulphur dioxide up into Earth’s atmosphere. Reaching 20 km in altitude, the gas formed small droplets of concentrated sulphuric acid, like those found in Venus’ clouds, which then spread around Earth. The droplets created a haze layer that reflected some of the Sun’s rays back into space, cooling the whole planet by about 0.5°C.

However, the new work on the evaporation of sulphuric acid on Venus suggests that such attempts at cooling our planet may not be as successful as first thought, because we do not know how quickly the initially protective haze will be converted back into gaseous sulphuric acid: this is transparent and so allows all the Sun’s rays through.

“We must study in great detail the potential consequences of such an artificial sulphur layer in the atmosphere of Earth,” says Jean-Loup Bertaux, Université de Versailles-Saint-Quentin, France, Principal Investigator of the SPICAV sensor on Venus Express. “Venus has an enormous layer of such droplets, so anything that we learn about those clouds is likely to be relevant to any geo-engineering of our own planet.”

In effect, nature is doing the experiment for us and Venus Express allows us to learn the lessons before experimenting with our own world.

Study assesses nuclear power assumptions

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A broad review of current research on nuclear power economics has been published in the Journal of Renewable and Sustainable Energy. The report concludes that nuclear power will continue to be a viable power source but that the current fuel cycle is not sustainable. Due to uncertainty about waste management, any projection of future costs must be built on basic assumptions that are not grounded in real data. “The goal of this study was to determine what assumptions are key to reaching conclusions about the relative costs of technologies,” says author Sarah Widder, now at Pacific Northwest National Laboratory. She performed the analysis as a science policy intern in Washington D.C. sponsored by the American Institute of Chemical Engineers . “The increasing world demand for uranium and political considerations such as the fate of the Yucca mountain disposal site are two major elements that drive conclusions in one direction or another.”

Reprocessing and recycling of spent fuel is an alternative to the “once-through” policy mandated by the 1982 Nuclear Waste Policy Act. While it would minimize high-level radioactive waste and recover additional value from the fuel, the option is controversial because of the risk of weapon proliferation and the significant cost of fuel recovery. Analyses supporting the once-through option assume a continuation in current waste management policies, although they rely on disposal at Yucca Mountain, which has now been deemed unsuitable by the current administration. Analyses supporting a closed fuel cycle, in which unused fuel is recovered and recycled, assume progress in developing new recovery technologies and an increase in uranium costs due to international competition for resources.

Duke scientists look deeper for coal ash hazards

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As the U.S. Environmental Protection Agency weighs whether to define coal ash as hazardous waste, a Duke University study identifies new monitoring protocols and insights that can help investigators more accurately measure and predict the ecological impacts of coal ash contaminants. “The take-away lesson is we need to change how and where we look for coal ash contaminants,” says Avner Vengosh, professor of geochemistry and water quality at Duke’s Nicholas School of the Environment. “Risks to water quality and aquatic life don’t end with surface water contamination, but much of our current monitoring does.”

The study, published online this week in the peer-reviewed journal Environmental Science and Technology, documents contaminant levels in aquatic ecosystems over an 18-month period following a massive coal sludge spill in 2008 at a Tennessee Valley Authority power plant in Kingston, Tenn.

By analyzing more than 220 water samples collected over the 18-month period, the Duke team found that high concentrations of arsenic from the TVA coal ash remained in pore water — water trapped within river-bottom sediment — long after contaminant levels in surface waters dropped back below safe thresholds. Samples extracted from 10 centimeters to half a meter below the surface of sediment in downstream rivers contained arsenic levels of up to 2,000 parts per billion – well above the EPA’s thresholds of 10 parts per billion for safe drinking water, and 150 parts per billion for protection of aquatic life.

“It’s like cleaning your house,” Vengosh says of the finding. “Everything may look clean, but if you look under the rugs, that’s where you find the dirt.”

The potential impacts of pore water contamination extend far beyond the river bottom, he explains, because “this is where the biological food chain begins, so any bioaccumulation of toxins will start here.”

The research team, which included two graduate students from Duke’s Nicholas School of the Environment and Pratt School of Engineering, also found that acidity and the loss or gain of oxygen in water play key roles in controlling how arsenic, selenium and other coal ash contaminants leach into the environment. Knowing this will help scientists better predict the fate and migration of contaminants derived from coal ash residues, particularly those stored in holding ponds and landfills, as well as any potential leakage into lakes, rivers and other aquatic systems.

The study comes as the EPA is considering whether to define ash from coal-burning power plants as hazardous waste. The deadline for public comment to the EPA was Nov. 19; a final ruling — what Vengosh calls “a defining moment” — is expected in coming months.

“At more than 3.7 million cubic meters, the scope of the TVA spill is unprecedented, but similar processes are taking place in holding ponds, landfills and other coal ash storage facilities across the nation,” he says. “As long as coal ash isn’t regulated as hazardous waste, there is no way to prevent discharges of contaminants from these facilities and protect the environment.”

Soil microbes define dangerous rates of climate change

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The rate of global warming could lead to a rapid release of carbon from peatlands that would further accelerate global warming. Two recent studies published by the Mathematics Research Institute at the University of Exeter highlight the risk that this ‘compost bomb’ instability could pose, and calculate the conditions under which it could occur.

The same Exeter team is now exploring a possible link between the theories described in the studies and last summer’s devastating peatland fires in Russia.

The first paper is published in the European Journal of Social Science and the second in Proceedings of the Royal Society A.

The first paper by Catherine Luke and Professor Peter Cox describes the basic phenomenon. When soil microbes decompose organic matter they release heat – this is why compost heaps are often warmer than the air around them.

The compost bomb instability is a runaway feedback that occurs when the heat is generated by microbes more quickly than it can escape to the atmosphere. This in turn requires that the active decomposing soil layer is thermally-insulated from the atmosphere.

Catherine Luke explains: “The compost bomb instability is most likely to occur in drying organic soils covered by an insulating lichen or moss layer”.

The second paper led by Dr Sebastian Wieczorek and Professor Peter Ashwin, also of the University of Exeter, proves there is a dangerous rate of global warming beyond which the compost bomb instability occurs.

This is in contrast to the general belief that tipping points correspond to dangerous levels of global warming.

Sebastian Wieczorek explains: “The compost bomb instability is a novel type of rate-dependent climate tipping point”.

The Exeter team is now modelling the potential impact of the compost bomb instability on future climate change, including the potential link to the Russian peatland fires.It is also working to identify other rate-dependent tipping points.

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