Ancient food webs developed modern structure soon after mass extinction

Researchers from the Santa Fe Institute and the Smithsonian Institution have pieced together a highly detailed picture of feeding relationships among 700 mammal, bird, reptile, fish, insect, and plant species from a 48 million year old lake and forest ecosystem.Their analysis of fossilized remains from the Messel deposit near Frankfurt, Germany, provides the most compelling evidence to date that ancient food webs were organized much like modern food webs. Their paper describing the research appears online and open access this week in Proceedings of the Royal Society B: Biological Sciences.The researchers first compiled data about the more than 6,500 feeding relationships among 700 species found in the deposit, which dates to the Eocene epoch. Then they constructed two networks of feeding interactions — one for the lake and one for the surrounding forest.Next, they mathematically compared each food web’s structural features with those of modern-day food web datasets — matching up such indicators as fractions of cannibals, herbivores, and omnivores; the distributions of generalist and specialist feeders; the mean lengths of feeding chains connecting pairs of taxa; and so on.”What we found is that the Messel lake food web, with 94 taxa and 517 links, looks very much like a modern food web,” says SFI Professor Jennifer Dunne. “This is despite the fact that 48 million years of species turnover and evolution separate the Messel lake ecosystem from modern ecosystems.”Analysis of the Messel forest food web’s structure was more challenging due to the high degree of species diversity represented in the Messel dataset — 630 taxa and 5,534 feeding links — far more than what datasets for modern webs include.”Basically, we don’t yet have examples of comprehensive modern terrestrial food web datasets that have the high resolution of plants, insects, and their interactions that we included in the Messel forest dataset,” says Dunne.Nevertheless, the researchers were able to show that the Messel forest web is likely comparable in structure to modern webs, by using models to account for differences in structure that would result from the many more taxa and interactions in the Messel data.The results are significant because they show that the Messel ecosystem developed a modern ecological structure, along with a modern biota, in a relatively brief 18 million year period following Earth’s most recent die-off, the end-Cretaceous mass extinction, which disrupted ecosystem dynamics on a massive scale and served as a species diversity bottleneck.Dunne says that beyond the ecological and evolutionary significance of the study, the work resulted in the most highly resolved, detailed, and comprehensive terrestrial food web ever compiled.”We want our data to serve as a challenge to ecologists to compile more highly and evenly resolved food web data for extant systems,” she says.Ancient food webs are particularly difficult to reconstruct because data about them is usually limited and of low quality. But the Messel shale deposit is unique. Scientists hypothesize that releases of toxic volcanic gases rendered the area’s air and water lethal to most life in a short time. Animals in and near the lake were overwhelmed, and, along with plants, sunk to the low-oxygen depths of the lake where they were smothered in mud and fossilized, soft tissue and all.The Messel includes outstanding evidence of feeding interactions, including stomach contents and bite marks in soft tissues that can be traced back to particular species’ mouth parts, Dunne says.”Compiling such a highly resolved food web was possible for the Messel because of the exquisite preservation of soft body parts and ecological traces in the deposit,” she says, “and because my co-author, Conrad Labandeira, is one of the world’s foremost experts on fossil plant-insect interactions.”Story Source:The above story is based on materials provided by Santa Fe Institute. Note: Materials may be edited for content and length.

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Ambitious new pollution targets needed to protect Lake Erie from massive ‘dead zone’

Reducing the size of the Lake Erie “dead zone” to acceptable levels will require cutting nutrient pollution nearly in half in coming decades, at a time when climate change is expected to make such reductions more difficult.That’s one of the main conclusions of a comprehensive new study that documents recent trends in Lake Erie’s health. It offers science-based guidance to policymakers seeking to reduce the size of toxic algae blooms and oxygen-starved regions called hypoxic zones, or dead zones — two related water-quality problems that have seen a resurgence in the lake since the mid-1990s.The report from the multi-institution EcoFore-Lake Erie project states that a 46 percent reduction in the amount, or load, of phosphorus pollution would be needed to shrink Lake Erie’s Central Basin hypoxic zone to a size last seen in the mid-1990s — a time that coincided with the recovery of several recreational and commercial fisheries in the lake’s west and central basins.Phosphorus is a nutrient used in crop fertilizers. Excess phosphorus washes off croplands during rainstorms and flows downstream in rivers that feed the Great Lakes. Once in the lakes, phosphorus can trigger algae blooms. When the algae die and sink to the lake bottom, oxygen-consuming bacteria feed on them and create hypoxic zones in the process. Many fish shun these oxygen-starved waters, which significantly reduce the amount of suitable habitat available to the fish.The study, accepted for publication in a forthcoming edition of the Journal of Great Lakes Research, calls for Central Basin phosphorus reductions considerably higher than other recent recommendations, including a proposal issued last year by the Ohio Lake Erie Phosphorus Task Force aimed at avoiding Western Basin toxic algae blooms. The new report is a synthesis of the major findings from the EcoFore-Lake Erie project, created in 2005 and supported by the U.S. National Oceanic and Atmospheric Administration’s Center for Sponsored Coastal Ocean Research.”The new target is very ambitious but is achievable if the region agrees to adopt agricultural practices that help reduce the amount of phosphorus-bearing fertilizer washing off fields,” said aquatic ecologist Donald Scavia, director of the University of Michigan’s Graham Sustainability Institute and EcoFore-Lake Erie principal investigator. “We believe this EcoFore synthesis report provides important input to the U.S. and Canadian teams charged with setting new phosphorus load targets for Lake Erie.”The EcoFore recommendations are aimed at policymakers who will update the binational Great Lakes Water Quality Agreement. …

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Competition breeds new fish species, study finds

Competition may play an important role during the evolution of new species, but empirical evidence for this is scarce, despite being implicit in Charles Darwin’s work and support from theoretical studies.Dr Martin Genner from Bristol’s School of Biological Sciences and colleagues used population genetics and experimental evidence to demonstrate a role for competition that leads to the differentiation of new species within the highly diverse cichlid fishes of Lake Tanganyika in East Africa.They found that the cichlid fish Telmatochromis temporalis shows two genetically distinct ecomorphs (local varieties of a species whose appearance is determined by its ecological environment), that strongly differ in body size and the habitat in which they live.Dr Genner said: “We found large-sized individuals living along the rocky shoreline of Lake Tanganyika and, in the vicinity of these shores, we found small-sized individuals, roughly half the size of the large ones, that live and breed in accumulations of empty snail shells found on sand.”According to the study, the bigger fish outcompete the smaller ones, driving them away from the preferred rocky habitats and into the neighbouring sand, where the smaller fish find shelter for themselves and their eggs in empty snail shells.”In effect, big and small fish use different habitats; and because of this habitat segregation, fish usually mate with individuals of similar size. There is virtually no genetic exchange between the large- and small-bodied ectomorphs,” Dr Genner commented.Speciation occurs when genetic differences between groups of individuals accumulate over time. In the case of Telmatochromis there are no obvious obstacles to the movement and interaction of individuals. But, the non-random mating between large- and small-bodied fish sets the stage for the evolutionary play.Dr Genner said: “The relevance of our work is that it provides experimental evidence that competition for space drives differential mating in cichlid fish and, in time, leads to the formation of new species. Nature has its ways — from body size differences to the formation of new species. And clearly, size does matters for Telmatochromis and for fish diversity.”Story Source:The above story is based on materials provided by University of Bristol. Note: Materials may be edited for content and length.

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Link between zebra mussels, risk of algae blooms

Researchers at Grand Valley State University’s Annis Water Resources Institute are learning more about the impact invasive zebra mussels and native aquatic insect larvae have on the risk of algae blooms in two West Michigan lakes. The results of the research will be published in the journal Oikos.Postdoctoral researcher Geraldine Nogaro and AWRI director Alan Steinman studied the impact that invasive zebra mussels and native chironomid larvae have on nutrient releases in Muskegon Lake and Bear Lake. While studying the mussels, Nogaro and Steinman noted that filter feeding and excretion activity by invasive mussels stimulated nutrient releases in the water column. The other subject of the research was the impact of native chironomids, which are insect larvae that live in the sediment on the lake bottoms. The researchers found the chironomids burrowed into the sediment, moving water and oxygen into the sediment and increased the levels of nutrients released into the sediment porewater and water column.”When nutrient levels increase, so does the risk of stimulated algae blooms,” Nogaro said. “The blooms are problematic because you can’t enjoy the lakes, and because certain blooms of cyanobacteria can release toxins into the water, which impacts fish and other wildlife.”Nogaro also said bacteria growing on decomposing algae blooms can suck up valuable dissolved oxygen in the lake, which can result in large fish kills in the affected areas.The research reinforces the need to monitor the numbers of mussels in the lake, along with the need to reduce human nutrient input into the ecosystem, including storm runoff that contains nonpoint source pollution.”These results have management implications, as the effects of invasive mussels on the biogeochemical functioning in the Great Lakes region and elsewhere can alter system bioenergetics and promote harmful algal blooms,” Steinman said.Story Source:The above story is based on materials provided by Grand Valley State University. Note: Materials may be edited for content and length.

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Wetland restoration in the northern Everglades: Watershed potential and nutrient legacies

Oct. 10, 2013 — To most people, restoration of Florida’s Everglades means recovering and protecting the wetlands of south Florida, including Everglades National Park. But what many don’t realize is how intimately the fortunes of the southern Everglades are tied to central Florida’s Lake Okeechobee and lands even further north.”The Everglades at the southern tip of Florida — the remains of what was once a vast ecosystem — is interconnected with a large hydrologic system that really begins in Orlando with the northern Everglades,” says Patrick Bohlen, a professor of biology at University of Central Florida. The heart of the system is Lake Okeechobee, he continues, which collects water from the northern Everglades region. This water then used to flow from the lake into the Everglades of the south.But this natural path of water has been greatly altered by people, leading to a host of environmental problems that state and federal scientists, policy makers, conservationists, and private landowners are now trying to solve. On Nov. 4, Bohlen will present “Wetland Restoration in the Northern Everglades: Watershed Potential and Nutrient Legacies.” His talk is part of the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America Annual Meetings, Nov. 3-6 in Tampa, Florida.One of the big challenges is nutrient pollution. Land in the northern Everglades is mostly privately owned, and urbanization and agriculture now send runoff laden with fertilizers and other contaminants into Lake Okeechobee. This nutrient-contaminated water would damage the delicate southern Everglades should it reach them. …

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Complex relationship between phosphorus levels, nitrogen removal in lakes

Oct. 10, 2013 — In the land of 10,000 lakes, one lake has been the starting place for research with implications for big lakes around the world. According to a study published online this week in Science, University of Minnesota researchers, building from studies of nitrogen levels in Lake Superior, uncovered a good news/bad news scenario for lake health that has long-term, global implications for pollution control efforts.While many water-quality cleanup efforts focusing on the reduction of phosphorus have been highly effective, that success can also result in a decrease in microbial processes that remove nitrogen from water. Nitrogen accumulation in large lakes can lead to nitrogen pollution downstream, in rivers and coastal areas. The findings suggest that human-caused acceleration of global nitrogen and phosphorus cycles have boosted nitrogen removal processes in small to medium-size lakes. But in many of Earth’s large lakes, these effects are reduced by successful control of phosphorus, resulting in nitrogen accumulation.”Freshwater ecosystems, including lakes, streams and wetlands, are a large global sink for reactive nitrogen,” says lead author Jacques Finlay, an associate professor in the College of Biological Sciences (CBS). “By reducing one aquatic pollutant — phosphorus — we are in some cases reducing the ability of lakes to remove nitrogen.” Gaston Small, an assistant professor at the University of St. Thomas, and Robert Sterner, a fellow CBS ecology professor, co-authored the study.To assess the influence of phosphorus on nitrogen removal, the researchers used a comparative approach — they examined the differences between how much nitrogen goes into lakes and how much comes out downstream — coupled with time-series analyses of nitrogen and phosphorus concentration in large lakes.”The work was motivated by our thinking about the case of a single lake — Lake Superior. This lake is one that we would expect to efficiently remove nitrogen, but it doesn’t, and it has extremely low phosphorus, so this work arose from efforts to generalize beyond a single system,” Finlay says.The excess nutrients can come from a variety of sources. City dwellers contribute nitrogen through sewage, lawn fertilizer, vehicle exhaust and pets. …

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Bringing light to a halt: Physicists freeze motion of light for a minute

Aug. 6, 2013 — Physicists in Darmstadt have been able to stop something that has the greatest possible speed and that never really stops. We’re talking about light. About a decade ago, physicists stopped it very for just a moment. In previous years, this extended towards stop times of a few seconds for simple light pulses in extremely cold gases and special crystals. But now the researchers at Darmstadt extended the possible duration and applications for freezing the motion of light considerably.The physicists, headed by Thomas Halfmann at the Institute of Applied Physics of the Technische Universität Darmstadt, stopped light for about one minute. They were also able to save images that were transferred by the light pulse into the crystal for a minute — a million times longer than previously possible.The researchers achieved the record by cleverly combining various known methods of their field. The result will have practical significance in future data processing systems that operate using light.To stop the light, the physicists used a glass-like crystal that contains a low concentration of ions — electrically charged atoms — of the element praseodymium. The experimental setup also includes two laser beams. One is part of the deceleration unit, while the other is to be stopped. …

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Particle accelerator that can fit on a tabletop opens new chapter for science research

June 20, 2013 — Physicists at The University of Texas at Austin have built a tabletop particle accelerator that can generate energies and speeds previously reached only by major facilities that are hundreds of meters long and cost hundreds of millions of dollars to build.”We have accelerated about half a billion electrons to 2 gigaelectronvolts over a distance of about 1 inch,” said Mike Downer, professor of physics in the College of Natural Sciences. “Until now that degree of energy and focus has required a conventional accelerator that stretches more than the length of two football fields. It’s a downsizing of a factor of approximately 10,000.”The results, which were published this week in Nature Communications, mark a major milestone in the advance toward the day when multi-gigaelectronvolt (GeV) laser plasma accelerators are standard equipment in research laboratories around the world.Downer said he expects 10 GeV accelerators of a few inches in length to be developed within the next few years, and he believes 20 GeV accelerators of similar size could be developed within a decade.Downer said that the electrons from the current 2 GeV accelerator can be converted into “hard” X-rays as bright as those from large-scale facilities. He believes that with further refinement they could even drive an X-ray free electron laser, the brightest X-ray source currently available to science.A tabletop X-ray laser would be transformative for chemists and biologists, who could use the bright X-rays to study the molecular basis of matter and life with atomic precision, and femtosecond time resolution, without traveling to a large national facility.”The X-rays we’ll be able to produce are of femtosecond duration, which is the time scale on which molecules vibrate and the fastest chemical reactions take place,” said Downer. “They will have the energy and brightness to enable us to see, for example, the atomic structure of single protein molecules in a living sample.”To generate the energetic electrons capable of producing these X-rays, Downer and his colleagues employed an acceleration method known as laser-plasma acceleration. It involves firing a brief but intensely powerful laser pulse into a puff of gas.”To a layman it looks like low technology,” said Downer. “All you do is make a little puff of gas with the right density and profile. The laser pulse comes in. It ionizes that gas and makes the plasma, but it also imprints structure in it. It separates electrons from the ion background and creates these enormous internal space-charge fields. …

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