High resolution techniques reveal clues in 3.5 billion-year-old biomass

To learn about the first organisms on our planet, researchers have to analyse the rocks of the early Earth. These can only be found in a few places on the surface of the Earth. The Pilbara Craton in Western Australia is one of these rare sites: there are rocks there that are around 3.5 billion years old containing traces of the microorganisms that lived at that time. A research team led by the University of Göttingen has now found new clues about the formation and composition of this ancient biomass, providing insights into the earliest ecosystems on Earth. The results were published in the journal Precambrian Research.

Using high-resolution techniques such as nuclear magnetic resonance spectroscopy (NMR) and near-edge X-ray Absorption Fine Structure (NEXAFS), the researchers analysed carbonaceous particles found rocks made of barium sulphate.

This enabled scientists to obtain important information about the structure of microscopically small particles and show that they are of biological origin.

It is likely that the particles were deposited as sediment in the body of water of a "caldera" -- a large cauldron-shaped hollow that forms after volcanic activity.

In addition, some of the particles must have been transported and changed by hydrothermal waters just beneath the surface of the volcano.

This indicates a turbulent history of sediment deposits. By analysing various carbon isotopes, the researchers concluded that different types of microorganisms were already living in the vicinity of the volcanic activity, similar to those found today at Icelandic geysers or at hot springs in Yellowstone National Park.

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Researchers shed light on river resiliency to flooding

Researchers at theUniversity of Nevada, Renohave completed one of the most extensive river resilience studies, examining how river ecosystems recover following floods. They developed a novel modeling approach that used data from oxygen sensors placed in rivers to estimate daily growth in aquatic plants and algae. The researchers then modeled the algal and plant biomass in 143 rivers across the contiguous U.S. to quantify what magnitude of flooding disturbs the biomass and how long the rivers take to recover from floods. Increased understanding of rivers' resiliency is important to maintaining healthy rivers, as human actions can affect flood regimes and change the conditions in rivers for other aquatic life that may rely on algae and plants as a food source.

Assistant Professor Joanna Blaszczak and Postdoctoral Scholar Heili Lowman, both in the University'sCollege of Agriculture, Biotechnology & Natural ResourcesandGlobal Water Centerled the research, which was published in two separate journal articles. The preliminary work, led by Blaszczak andpublished in Ecology Letters last June, first studied six rivers and laid the groundwork and methodology for the second study, which Blaszczak hired Lowman to conduct, examining the 143 rivers. The results of that research were justpublished last month in PNAS (the Proceedings of the National Academy of Sciences).

The research is unique because it estimates changes in biomass in rivers more frequently than ever before without needing to directly sample rivers. This is done by using both data from oxygen sensors placed in the rivers by the U.S. Geological Survey and a population model of algal and plant biomass -- similar to a human population model that models change in the number of people over time, but instead modeling the change in the amount of algae and plants. The oxygen sensors began collecting data in 2007, and the most recent Nevada-led study of 143 rivers includes some data that are for nine years running, among the longest such records on file for rivers across the globe.

"Previously, you would have to go to a river and scrub rocks to measure the algae, and do that several times for an extended period of time in order to estimate changes in biomass growth and loss," Blaszczak said. "This is very time consuming, so the data have been extremely limited relative to how extensive our sensor networks are."

Blaszczak said that with the oxygen sensors that take data as frequently as every five minutes, the team found that they could use statistical models to extract the amount of photosynthesis that occurs daily and estimate daily changes in the amount of biomass in a river over time.

"The dissolved oxygen sensors show the peak during the day, and the low during the night, and from those patterns, you can estimate how much new algae and other biomass grew that day," she said. "With the sensors measuring data continuously in hundreds of rivers for years now, we can get a much bigger, clearer picture. The data is there, and we can use it to model the size of flood needed to disturb the biomass in a river, as well as the rate at which a river recovers from flood disturbances, which can help us manage rivers more effectively."

Getting started

In the first study, Blaszczak used two years of data from oxygen sensors placed in six rivers. She found that she could successfully use this data to model the flood threshold specific to a river that disturbed the underlying biomass, and that generally, the magnitude of flood necessary to disturb biomass and reduce ecosystem productivity was lower than the disturbance flow threshold necessary to mobilize river bed sediment, a metric of disturbance commonly used by those studying rivers. In other words, instead of estimating the disturbance of the river by the movement of the rocks on the river bed, this study used the biology -- the changes in algae and plant growth -- to quantify disturbance to the river and found that the biological disturbance threshold was lower.

"The amount of biomass is important for water quality and a food source for everything that lives in a river," Blaszczak explained, "so it is more important than rock movement, in terms how a river ecosystem is affected by a disturbance."

Blaszczak, a freshwater ecologist, began this work with Robert O. Hall Jr. of the Flathead Lake Biological Station at the University of Montana and enlisted the help of her colleague Assistant Professor Robert Shriver, a plant ecologist, for both research projects to complete the biomass growth modeling. Blaszczak, Shriver, and Lowman all conduct research as part of the College'sDepartment of Natural Resources & Environmental Science, as well as the College'sExperiment Stationresearch unit. The College's faculty often take interdisciplinary approaches to meet research challenges, Blaszczak said.

Expanding out to a continental scale

Blaszczak wanted to delve further by applying this approach to more rivers over a longer period of time to shed light on how various factors may be influencing both a river's thresholds for flood disturbance and its resilience to floods. Thus, she recruited Lowman to embark on the second, more extensive study. Lowman's research examined landscape and river characteristics that affected the rivers' resiliency to floods.

"We've never had such great insight into the resilience of rivers, and because of the amount of data and our modeling, we now understand the natural variation in resilience, and that the widest rivers without dams upstream recover the most quickly," Lowman said.

The fact that wide rivers without dams recover more quickly than wide rivers with dams upstream was not immediately obvious, she said, and is one example of how rivers can be affected and/or managed by our actions. Most of the rivers Lowman researched had three to four years of data, with some having as much as nine years, and a handful having less than a year.

"Having three to four years' worth of data is way more than we've ever been able to use before," Lowman said. "And, we used rivers of various sizes with various climates and land characteristics."

Besides wider rivers without dams being more resilient, Lowman said those rivers that had more frequent floods also tended to recover more quickly.

"It could be that they have had a long history of frequent flooding, so their algae and plant communities have developed the ability to adapt to more frequent disturbance," she said.

Overall, Lowman said the new model results are consistent with other previous approaches. But, she said that some sites took much longer, a month or more, to recover from floods than other sites, regardless of river size.

"It might be the composition of the algal and plant communities, the structure of the river bed, or other factors," she said. "The thresholds and recovery times are very likely partially dependent on the slope, the grain size of the sediment, and possibly other factors that aren't as well documented. Those are some next steps for future research."

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Earth prefers to serve life in XXS and XXL sizes

Life comes in all shapes in sizes, but some sizes are more popular than others, new research from the University of British Columbia has found.

In the first study of its kind published today in PLOS ONE, Dr. Eden Tekwa, who conducted the study as a postdoctoral fellow at UBC's department of zoology, surveyed the body sizes of all Earth's living organisms, and uncovered an unexpected pattern. Contrary to what current theories can explain, our planet's biomass -- the material that makes up all living organisms -- is concentrated in organisms at either end of the size spectrum.

"The smallest and largest organisms significantly outweigh all other organisms," said Dr. Tekwa, lead author of "The size of life," and now a research associate with McGill University's department of biology. "This seems like a new and emerging pattern that needs to be explained, and we don't have theories for how to explain it right now. Current theories predict that biomass would be spread evenly across all body sizes."

In addition to challenging our understanding of how life is distributed, these results have important implications for predicting the effects and impacts of climate change. "Body size governs a lot of global processes as well as local processes, including the rate at which carbon gets sequestered, and how the function and stability of ecosystems might be affected by the composition of living things," said Dr. Tekwa. "We need to think about how body size biomass distribution will change under environmental pressures."

"Life constantly amazes us, including the incredible range of sizes that it comes in," says senior author Dr. Malin Pinsky, associate professor in the department of ecology, evolution, and natural resources at Rutgers University. "If the tiniest microbe was the size of the period at the end of this sentence, the largest living organism, a sequoia tree, would be the size of the Panama Canal."

To obtain their results, Dr. Tekwa spent five years compiling and analyzing data about the size and biomass of every type of living organism on the planet -- from tiny one-celled organisms like soil archaea and bacteria to large organisms like blue whales and sequoia trees. They found that the pattern favouring large and small organisms held across all types of species, and was more pronounced in land-based organisms than in marine environments. Interestingly, maximum body size seemed to reach the same upper limits across multiple species and environments.

"The largest body sizes appear across multiple species groups, and their maximum body sizes are all within a relatively narrow range," Dr. Tekwa noted. "Trees, grasses, underground fungi, mangroves, corals, fish and marine mammals all have similar maximum body sizes. This might suggest that there is a universal upper size limit due to ecological, evolutionary or biophysical limitations."

Dr. Tekwa was also able to uncover some intriguing details about the distribution of life in various ecosystems. "Even though corals occur in only a small fraction of the ocean, it turns out that they have about the same biomass as all the fish in the ocean," said Dr. Tekwa. "This illustrates how important the balance of biomass is in the oceans. Corals support a lot of fish diversity, so it's really interesting that those two organisms have almost the same biomass."

As for humans, we already know we comprise a relatively small biomass, but our size among all living things reveals our place in the global biome. "We belong to the size range that comprises the highest biomass, which is a relatively large body size," said Dr. Tekwa.

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