Tag Archives: sediment

Mountain streams aren’t pristine any longer — not when humans move in

Mountain spring water isn’t as clean or fresh as we like to assume, according to new research.

Data collected over four decades shows that the quality of water in high-elevation (mountain) streams has been steadily decreasing over time. The issues underlying this decline are both historical and modern, related to man-made developments in hilly and mountainous landscapes.

The main sources of pollutants in mountain streams are sediment from unpaved, rural roads, and agricultural runoff.

No longer pristine

“We had access to studies from 1976 to last year that encompassed both stream and terrestrial studies,” said Rhett Jackson, a professor at UGA’s Warnell School of Forestry and Natural Resources and the paper’s lead author. “Some streams in Macon County have very high sediment concentrations, four times greater than found in forested streams.”

The findings are based on data from the U.S.’ Southern Appalachian area. Streams here still carry the signs of environmental changes caused by European settlers moving into the region during the 1900s, the authors report.

Native Americans, the original inhabitants of the Southern Appalachians, traditionally only farmed the valleys strewn along this mountain chain. They left the hills and mountain slopes undeveloped as woodlands, where they would hunt and gather wild fruits and plants.

When settlers moved in, however, they engaged in heavy logging, to obtain timber for trade and construction, and to clear space for farmland. This process significantly changed the landscape of the area’s hills and mountain slopes. New farmland established on the hills promoted erosion, and the sediment produced by that erosion was gradually cleaned away by rainfall into high-altitude streams.

Even today, the authors explain, streambeds in the Southern Appalachians carry those century-old bodies of sediment, under layers of fresh material that is still making its way into their courses.

High levels of sediment affect the wild animals living in the streams, Jackson explains. For starters, it makes it harder for animals to find food as it makes the waters murky. It also has a direct impact on fish growth and their ability to resist disease.

Sediment builds up downstream as well, making its way into public water supplies. As such, there’s a direct financial cost to communities, as these impurities need to be filtered out before water can be pumped to taps around towns and cities.

The team underscores that these changes in sediment input into high-altitude streams first started manifesting over one century ago, and are the result of environmental changes caused by increased habitation due to settlers moving into the area.

“The landscape you see now isn’t what it was like in 1900—the early settlers logged everything,” said Jackson.

Although the first settlers started this process, their descendants today are carrying the torch. Starting with the 1980s, for example, the area saw a massive rise in interest for the development of the steep (and previously wild) mountain slopes. A large number of vacation residences and villas were built on these slopes, generating significant land disturbance through the buildings themselves and associated infrastructure — the carving out of roads. Such development made the area rife for landslides, and the unpaved roads that reached these buildings produced ample dust.

“Roadside ditches and unpaved roads produce a lot of sediment, [which] increases as roads get steeper and as gravel roads get more use,” said Jackson.

The authors report that while a typical stream in the southern Appalachian forest contains around 8 to 10 milligrams of sediment per liter, in areas with both mountain and hill development, they have found concentrations of sediment between four to six times this value.

Farming also plays a part. Runoff from farms introduces a high level of nitrates into mountain streams. Levels of these compounds are particularly high for streams running past pastures that do not enjoy a buffer of trees to absorb some of the fertilizer. Deforestation further impacts the health of wild communities in these streams as the lack of shade leads to higher average water temperatures, which can be damaging for trout and other local species that are adapted to cold waters. Around 40% of the streams in the study area have lost their buffer of trees, the team reports.

“On small streams, the actions of individual landowners matter a lot,” he said. “Sometimes, we see unusual streamside activities [such as illicit discharge pipes or streams diverted through animal enclosures] with substantial water quality effects.”

“Because the water in streams comes from the whole landscape, everything we see on the land has some effect on streams. But streams are resilient, and as long as we intelligently modify our actions a little bit, we can farm and live near streams while protecting their water quality. Maintaining the quality of our landscape requires a little thought and work on our parts.”

Taking small, simple steps, such as planting rows of trees near an open stream, or making sure to buffer runoff from a gravel road, can help a great deal in improving the water quality of open streams, the team concludes.

The paper “Distinctive Connectivities of Near-Stream and Watershed-Wide Land Uses Differentially Degrade Rural Aquatic Ecosystems” has been published in the journal BioScience.

Staghorn coral.

Miami dredging caused “extensive coral mortality and critical habitat loss” for the US’ only continental reef

Researchers at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science say that local reefs have suffered extensive damage from sediment plumes stirred up by the 16-month dredging operation at the Port of Miami.

Sediment plume.

Natural sediment plumes from the Mississippi River (right) and the Atchafalaya River (left).
Image credits NASA.

The team estimates that over half a million corals were killed — those that lived within 550 yards (500 meters) of the dredged channel. Dredging operations, which involve clearing the seabed by scooping out mud, weeds, and rubbish with a dredge, seem to have impacted more than 15 miles (25 kilometers) of Florida’s reef tract, resulting in widespread coral death.

Deadly dredging

“Coral reefs worldwide are facing severe declines from climate change,” said Andrew Baker, associate professor of marine biology and ecology at the UM Rosenstiel School and senior author of the study. “If we want to conserve these ecosystems for the generations that come after us, it’s essential that we do all we can to conserve the corals we still have left.”

“These climate survivors may hold the key to understanding how some corals can survive global changes. We have to start locally by doing all we can to protect our remaining corals from impacts, like dredging, that we have the ability to control or prevent.”

Dredging operations at the Port of Miami began in 2013 as part of a larger construction effort in the area. The team analyzed data that was originally collected by consultants as part of the dredge’s environmental monitoring program. This program did note the loss of coral in the area but wrote it off as the consequence of a coral disease that was making a region-wide outbreak at the same time.

The present research ruled out disease by controlling for its impacts: the team looked at losses in coral species that were known to be immune to the outbreak. They tested whether corals closer to the dredge site were more likely to die during the dredging period than those further away. Most of the documented coral losses near the Port of Miami were the result of dredging, the team found.

Staghorn coral.

Staghorn coral, a species of coral in the Florida Reef.
Image via Wikimedia.

“It was important to differentiate these multiple impacts occurring on the reefs to understand the direct effects of dredging specifically,” said lead author Ross Cunning, who began the project while a postdoctoral scientist at the UM Rosenstiel School and is now a research biologist at the Shedd Aquarium in Chicago.

“We brought together all the available data from satellites, sediment traps, and hundreds of underwater surveys. Together, the multiple, independent datasets clearly show that dredging caused the major damages observed on these reefs.”

The team also looked at sediment plumes, which are clouds of suspended sediment stirred up by the dredges — the team reports they’re big enough to be seen from space — and whether they could predict the damage observed on the reefs below. It turns out that they could; the team says that the satellite-tracked plumes had a very high correlation with coral death on the seafloor. This is the first study to show that satellite data can be reliably used to predict dredging impacts on corals and their habitats.

“This connection allowed us to predict impacts beyond where ship-based monitoring was taking place, and showed that dredging likely damaged this reef several kilometers away,” said study co-author Brian Barnes of the University of South Florida.

“While this same relationship may not apply in all projects, this is a remarkable finding that further establishes Earth-observing satellites as independent monitoring tools to fill in gaps where data are otherwise not available.”

Rachel Silverstein, executive director and waterkeeper of Miami Waterkeeper and a co-author of the study says the study uncovered a “devastating story of loss that we cannot afford to ignore any longer.” She hopes that the team’s findings can be used to guide restoration efforts and to prevent similar tragedies in the future.

Florida can boast the only nearshore reef in the continental United States, but its coral cover has declined by at least 70% since the 1970s, the team explains. Some species in this reef — Staghorn corals (Acropora cervicornis), which were once common in shallow water and have declined by an estimated 98% — are now listed as threatened under the Endangered Species Act. The sites directly adjacent to the dredge site have been designated as “critical habitat” for the staghorn corals.

The paper “Extensive coral mortality and critical habitat loss following dredging and their association with remotely-sensed sediment plumes,” has been published in the journal Marine Pollution Bulletin.

NASA’s study of the Louisiana Deltas yields fantastic images of new land being born

A NASA team showed that aircraft-mounted instruments such as radar or lidar can be used to study the development of growing deltas. Using this method they followed the evolution of the Atchafalaya basin’s coastline, where two river deltas are growing into the Gulf of Mexico, over the last 30 years.

Image credits NASA / Earth Observatory.

Louisiana is sinking

Well, it’s actually subsiding under the Gulf of Mexico’s waters at a rate of about 18 sq miles (46.6 sq km) each year. But two areas of the coast are refusing to go down — Atchafalaya River and its diversion channel, Wax Lake Outlet, each have growing deltas that gain 1.5 and 2 square miles every 11 and 8 hours respectively.

This area has been under intense observation last fall, as a team from NASA’s Jet Propulsion Laboratory in Pasadena used radar, lidar, and a host of other aircraft-mounted instruments to study the growing deltas. Their work proves that airborne observation of such environments is possible and can be accurate while collecting data helps scientists better understand how coasts respond to a rising sea level.

Deltas have been lying around ripe for observation for a long time now, so we have a pretty good understanding of the basic mechanisms that power their growth. But even NASA finds it “hard to do research in a swamp”, so there’s a lot we still don’t understand — the effect different vegetation types have on their development, or what role tides and currents play.

“These factors are usually studied using boats and instruments that have to be transported through marshy and difficult terrain,” said Christine Rains, assistant flight coordinator for the program at JPL.

“This campaign was designed to show that wetlands can also be measured with airborne remote sensing over a large area.”

Mapping the delta

The Louisiana coastline with the two growing deltas, Wax Lake and Atchafalaya, circled in red. The Mississippi River flows to the east of the delta (righ-most blue squiggly line).
Image credits USGS / NASA.

At least once a year, JPL researchers do a fly-over of the Louisiana coast to track subsidence changes and keep an eye out on the levees. So last fall, they re-tasked these flights to focus on observing the growing deltas, especially vegetation and water flow patterns. They did this because, in a delta, water doesn’t flow one way — it flows in every direction. Incoming tide pushes water into the swampy lowland and can send water back uphill.

“Water flows not only through the main channels of the rivers but also through the marshes,” explained JPL’s Marc Simard, principal investigator for the campaign.

As the tide recedes, this water carries organic-rich sediment from the marshes into the river. JPL’s project measured these flows during both rising and falling tides. It also recorded the slope of the water and mapped the riverbed — which control the rivers’ flow speeds — from its origin in the Mississippi River all the way to the ocean.

The results show that airborne monitoring of deltas is feasible, and yields high-resolution results. It also highlighted that some species of marsh vegetation are more resistant to the flow of water than others.

“We were really surprised and impressed by [the findings]. In some places, the water changes by 10 centimeters [4 inches] in an hour or two. In others, it’s only three or four centimeters [1 to one-and-a-half inches]. You can see amazing patterns in the remote sensing measurements.”

The next step is to use these measurements to improve models of how water flows through marshlands. These models form the backbone of our predictions on how coastal marshes will cope with global sea level change.

“Our models will have to catch up with the observations now,” Simard added.

The slideshow NASA put together with the deltas’ growth over the past 30 years is pure eye candy, so check it out:

[button url=”http://earthobservatory.nasa.gov/Features/WorldOfChange/wax_lake.php” postid=”” style=”btn-danger” size=”default” target=”_self” fullwidth=”false”]Take me to NASA![/button]

 

 

8,000 Year Old Wheat Found in UK, 2,000 Years Before They Started Growing it

According to a new study, ancient hunter-gatherer Britons imported wheat from mainland Europe, showing a surprising level of sophistication for such an old population.

Image credits: Leonard Coldwell.

Wheat growing emerged at that fuzzy line where Europe meets Asia 12,000 years ago and then slowly spread across Europe. However, being so far away and separated by a growing line of water, Britain was one of the last places in Europe to adopt this practice. From what we know, Britons only grew wheat 6,000 years ago, so this evidence shows that they were importing it way before they were growing it.

“These results suggest that sophisticated social networks linked the Neolithic front in southern Europe to the Mesolithic peoples of northern Europe,” the researchers concluded. “There was a real cultural link between the ancient Britons and Europe,” said Robin Allaby, of the Univ. of Warwick, who led the study. “So Mesolithic people were not simply and quickly replaced by Neolithic peoples. Instead there was a long period — thousands of years — of interaction between the two.”

Eight millennia ago, Europe might have looked very differently than it does today – in fact, some geologists argue that Britain was still connected to the mainland through a land called Doggerland. But even if a land bridge did exist, the fact that such cultural (and maybe even economic) interaction existed is quite surprising. Allaby and evolutionary geneticist at the University of Warwick, continued:

“We were surprised to find wheat. This is a smoking gun of cultural interaction. It will upset archaeologists. The conventional view of Britain at the time was that it was cut off. We can only speculate how they got wheat — it could have been trade, a gift or stolen.”

Researchers found fragments of wheat DNA recovered from an ancient peat bog, alongside numerous other DNA fragments from wolves, dogs, deer, poplar, beech, and oak woods. However, no wheat pollen was found from the site, suggesting the plant was not grown nearby. Furthermore, wheat species are endemic to the Middle East so it’s extremely unlikely that they were grown locally. To make things even more interesting, archaeologists found DNA of (likely domesticated) pigs – a staple of Germany in those times.

It seems that a relatively advanced population of farmers arrived in Britain, encountering the local hunter-gatherers. They either traded, gifted or were robbed of their possessions and then left; if they had stayed, they would have likely began cultivating wheat or growing pigs.

Simone Riehl, an archaeologist at Tuebingen Univ. in Germany who also wasn’t involved in the study, said extracting DNA from sediment could revolutionize our understanding of ancient cultures, especially in areas where such evidence is scarce or where it was covered by water.

“The interpretation of ancient DNA signatures from such sediments however will probably remain debatable for a long time,” said Riehl.

The recovered DNA (of the wheat-known as einkorn) was collected from sediment that was once a peat bog next to a river. Since no grains were found in the sediment, the DNA probably came from wheat flour

“Probably the people would use such a product to make a dough. It is a simple matter to add water to flour, resulting in a flatbread which they could eat,” he said.

Journal Reference: Oliver Smith, Garry Momber, Richard Bates, Paul Garwood, Simon Fitch, Mark Pallen, Vincent Gaffney, Robin G. Allaby. Sedimentary DNA from a submerged site reveals wheat in the British Isles 8000 years agoDOI: 10.1126/science.1261278

52.000 year old forest discovered underwater [stunning pictures and video]

Scuba divers have discovered a primeval underwater forest off the coast of Alabama – a cypress forest which was incredibly well preserved for over 50.000 years.

underwater forest1

The bald cypress forest was buried under ocean sediments (almost certainly sand), isolated from oxygen (which is the main enemy of preservation), thus preventing them from rotting; however, the underwater forest was uncovered by hurricane Katrina, in 2005, explains Ben Raines, one of the first divers to explore it.

“Swimming around amidst these stumps and logs, you just feel like you’re in this fairy world,” Raines said.

The trees are so well preserved that when cut, they still smell like fresh cypress! The remaining stumps of the small forest cover an area of over 1.3 km, and lie about 18 meters below the surface of the Gulf of Mexico. The bad news is that even though it was recently discovered, now that it is subject to the action of oxygen and marine animals, it will only take another few years before it is destroyed. Even as little as two years could destroy it.

underwater forest21

“The longer this wood sits on the bottom of the ocean, the more marine organisms burrow into the wood, which can create hurdles when we are trying to get radiocarbon dates,” Harley said. “It can really make the sample undatable, unusable.”

The forest was dated with the help of carbon isotopes, but the trees’ rings can offer valuable information about the climate of the Gulf of Mexico thousands of years ago, during a period known as the Wisconsin Glacial period, when sea levels (and temperatures) were much lower than they are today.

 

“These stumps are so big, they’re upwards of two meters in diameter — the size of trucks,” Harley explained. “They probably contain thousands of growth rings.”

Medieval tsunamis in the Alps – could happen again

If you think about tsunamis, you’ll probably think about Japan, Indonesia, maybe America… the last place you’d image would be the Alps, right? Well, you might have to go back to that.

About 1500 years ago, a massive flood took place in Geneva, Switzerland, wiping out everything in its path, crippling the local community. Now, researchers believed they found the culprit in the form of a tsunami, a threat which is still pretty much posed today. The presumed wave was caused by a huge landslide, wrecking the entire medieval city, which was probably already a known trading hub at the time.

Far from the ocean, the massive wave had its origin in the Rhône River, which feeds and flows through Lake Geneva. The Swiss team analyzed a huge sediment deposit at the bottom of the lake and came to the conclusion that it once belonged above the lake and slid into the Rhône near the place it flows into the lake. The sudden splash created a tsunami that flower through the 580-square-kilometer lake towards Geneva, the study suggests; the height would have been between 3 and 8 meters, quite enough for that period.

But perhaps more important, researchers warm, is that this danger isn’t a thing of the past. A similar event happening today would cause much greater damage, significantly affecting not only Geneva, but also the neighboring cities of Lausanne, Nyon, and Thonon-les-Bains, threatening over 300.000 people who live in the area. The damage could be amplified by the fact that towards Geneva, the lake narrows, creating a funnel effect which acts as an amplified for waves. Still, there’s no need to panic, because there isn’t any hint of an immediate threat. Still, it is something to consider.

“If this has happened five to six times since the last glaciation, there’s reason to believe it could happen again in the future,” said University of Geneva geologist Guy Simpson, who study team’s modeler. “A three-meter [ten-foot] wave that hit Geneva today would be a scary wave.”

The research will be published in Nature

Chikyu sets a new world drilling-depth of scientific ocean drilling

The Japanese scientific deep sea vessel Chikyu managed to set a new world record by drilling down to over 2.200 meters below the seafloor, obtaining samples from Shimokita Peninsula of Japan in the northwest Pacific Ocean.

Drilling for science

Whenever you hear about drilling, it’s almost always about oil. Given the humongous amount of oil we use nowadays, it makes sense there are over 3.000.000 active oil rigs in the world – just mind blowing! Still, scientific drilling, despite neglected by comparison, has some remarkable accomplishments.

Typically, scientific drilling is used for recovering probes, samples of sediments, crust, and even upper mantle in extreme cases. Researchers are also able to study, in some cases, microbial life preserved in the samples. Especially recently, scientific drilling is going through a revolution, and its results are constantly improving in recent years, Chikyu being a clear example of that; until now, sea drilling was used without a a riser. Riser-less drilling uses seawater as its primary drilling fluid, which is pumped down through the drill pipe, cleaning and cooling the drill bits, piling them in a cone around the hole. However, Chikyu uses a riser, and the whole technology, although more complicated, also becomes more efficient, as you can see in the picture above.

A new era for scientific drilling

Chikyu – dawning a new era in scientific drilling

Chikyu made this achievement during the Deep Coalbed Biosphere expedition, Expedition 337, conducted as part of an international effort, the Integrated Ocean Drilling Program (IODP).

“We have just opened a window to the new era of scientific ocean drilling”, Fumio Inagaki, Co-Chief scientist of Expedition 337, says. “The extended record is just a beginning for the Chikyu. This scientific vessel has tremendous potentials to explore very deep realms that humans have never studied before. The deep samples are precious, and I am confident that our challenges will extend our systematic understanding of nature of life and earth.”

His European colleagues are just as thrilled:

“I am very glad that I am here today and could witness this wonderful and important moment. Everybody on the ship worked really hard to make this happen. And, I am very pleased about the high quality of the core samples, which show only minimal drilling disturbance. This is very important for our research.”, added Co-Chief scientist Kai-Uwe Hinrichs from the University of Bremen, Germany.

Samples retrieved featured mostly deeply buried coal – its formation was the main purpose of the expedition, and researchers hope it will be able to provide new insight regarding how deep life is associated with a hydrocarbon system in a deep marine subsurface.