Adrift along the Sundarbans mangroves, east India

Mid March 2021, I set out with 2 other wildlife enthusiasts to explore the Sundarbans delta in east India. The 3-hour journey from Kolkata city, on a busy road fringed by industrial towns tapered off at Gadkhali port – civilization’s last ‘land’ frontier before the largest  continuous mangrove stretch in the world. We arrived after dusk, boarded our boat (with a crew of 2 naturalists, 3 boatmen, and a chef!), and were adrift upon dark waterways guided by twinkling village lights. In our haste, we thought little of just how ‘remote’ this wilderness was. 

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What Lies Beneath: Tracing Magma Interactions Within Earth’s Crust

Featured Image: Yosemite National Park, California, USA by Thomas H. from Pixabay 

Paper: Feldspar recycling across magma mush bodies during the voluminous Half Dome and Cathedral Peak stages of the Tuolumne intrusive complex, Yosemite National Park, California, USA

Authors: Louis F. Oppenheim, Valbone Memeti, Calvin G. Barnes, Melissa Chambers, Joachim Krause, and Rosario Esposito

Earth’s landscapes provide evidence of the geological processes which have shaped it over the past 4 billion years.  The Earth’s crust, our planet’s outermost layer, preserves an extensive record of these processes. Within the crust igneous rocks which were once molten at depth and fed active volcanic eruptions, preserve evidence of the inner workings of volcanoes. These inner workings or “magmatic plumbing systems” are the focus of recent work by Oppenheim et al. (2021). In this work, Oppenheim and co-authors studied the crystal record of fossilized plumbing systems in order to provide new insights into the storage conditions and transport mechanisms of magma within Earths’ crust.

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Do Hurricanes Choke on Dust?

Satellite image showing plume of dust drifting from north Africa

Paper – Influence of Saharan Dust on the Large‐Scale Meteorological Environment for Development of Tropical Cyclone Over North Atlantic Ocean Basin
Authors – Yue Sun and Chuanfeng Zhao

Several times a year, strong gusts blow dust from the Sahara Desert westwards over the Atlantic Ocean. When the plume reaches the Caribbean, many residents experience respiratory irritation and allergic reactions to the dust. On particularly bad days, those with sensitivities to or certain pre-existing conditions are urged to stay indoors. The haze reduces visibility and casts a dull filter over the landscape.

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Taking the measure of the measurer

Featured image: A USGS “Did you feel it?” map for a M6.5 earthquake that occurred in the Monte Cristo Range in Nevada on May 15th, 2020 (public domain)

Paper: Which earthquake accounts matter?
Authors: Susan E. Hough and Stacey S. Martin

Seismologists who study earthquakes spend much of their time looking at wiggly lines that represent recordings of ground motion from seismometers, but in places where those data aren’t available, we often turn to what we call “macroseismic” data: eyewitness accounts from people who felt the shaking. But when we ask people on the ground, “Did you feel it?,” who is answering?

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Plants may help solve the climate crisis, but is there enough water for everyone?

Featured image: Sugarcane plantation to produce ethanol in Brazil by José Reynaldo da Fonseca on Wikipedia under CC BY 2.5.

Paper: Stenzel, F., Greve, P., Lucht, W. et al. Irrigation of biomass plantations may globally increase water stress more than climate change. Nat Commun 12, 1512 (2021). https://doi.org/10.1038/s41467-021-21640-3

In order to mitigate the effects of the climate crisis, we must stay under a 1.5℃ average global temperature increase from pre-industrial levels. To help reach this goal, there is growing interest in “negative emission technologies”, which are methods of removing greenhouse gases, like carbon dioxide, from the atmosphere. These carbon capture technologies have been around since the 1970s, but the best carbon capture technology might be as simple as plants.  Fabian Stenzel and his team explain that cultivating fast-growing plant species, processing them into biomass, and capturing any emitted carbon dioxide therein, would actually result in negative emissions. Specifically, creating biomass through this method can capture upwards of 2 gigatons of carbon per year by 2050 (that’s close to the mass of 12 million blue whales). Burning this would also unlock an incredibly energy dense source of power. While burning the biomass would inevitably release carbon dioxide into the atmosphere, the process of growing it would drastically offset this by removing a much larger amount. However, one crucial question needs to be answered: will we have enough water to pull it off?

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You are what you eat…and also where you fish

Article: Why productive lakes are larger mercury sedimentary sinks than oligotrophic brown water lakes

Authors: Martin Schütze, Philipp Gatz, Benjamin‐Silas Gilfedder, Harald Biester

Advisories and outreach campaigns have worked for years to help us understand how the fish we eat impacts the amount of hazardous mercury we consume. Mercury is present in the environment naturally in several forms, but consumption advisories warn against methyl-mercury. This substance not only moves throughout the aquatic ecosystem, but bio-accumulates, or increases in concentration, as it moves higher in the food chain.  But the size of the fish is not the only influence on its mercury levels – it may also matter where it lives. 

Most mercury in lakes is initially deposited from the atmosphere. These levels vary regionally, influenced by things like weather patterns and local industry. Mercury is also deposited on land, though, and it can eventually leach and erode from soils, moving through surface and groundwater into local lakes. Researchers have known for some time that the vegetation and soil types in the watershed can influence mercury influx to lakes; for example, coniferous trees generally take up more mercury from the atmosphere than deciduous trees, making the forest litter and, eventually, the organic rich layers of forest soils more concentrated in mercury in coniferous forests. 

A recent German study compared mercury levels in two sets of lakes, looking at everything from surrounding vegetation and topography to local weather patterns, and found that previously observed findings held up; mercury levels were higher in leaf litter and organic soils than other surrounding sediments, and higher in areas with more coniferous vegetation. However, when the authors undertook mathematical modelling to balance the input of mercury from atmospheric deposition and local erosion to the outflow, the numbers didn’t add up the same way in all the lakes.

The difference, they documented, was in the productivity of the lakes. Algae scavenge mercury from the water column and, when they die and sink, take the mercury along. This leads to mercury deposition in the lake sediments. By comparing measurements of mercury in the water column, in accumulated sediments on the lake floors, and in sediment ‘traps’ that collect sediment as it is falling through the water column, the researchers showed that large algal blooms significantly increase the transport of mercury from the water column into lake sediments. In a set of forested, alpine lakes that were low in nutrients and had few algal blooms, the monitoring data showed that most of the mercury inputs were eventually lost to a combination of river outflow, re-emission to the atmosphere, and sediment burial. In lakes with higher nutrient loads and more common algal blooms, a similar input of mercury was translated into a much higher flux to the lake sediments, which they traced to the concentration of mercury in the algal organic matter.

The high rate of mercury delivery to lake sediments, especially in very productive lakes, may be bad news for fishing. The high rate of organic matter input to the sediment also leads to a low-oxygen environment which can spur the bacterially-mediated chemical process that turns mercury into the methyl-mercury form. When it is released and recycled from the sediments, it works its way up the food chain. Lakes in many parts of the world are seeing increased algal growth from warmer temperatures and higher nutrient input, and the resultant highly-visible algal blooms may have a significant impact on the invisible movement of hazardous mercury to consumers at the top.


You are what you eat…and also where you fish by Avery Shinneman is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

How does climate change impact extreme cold outbreaks in the United States?

Featured image from CJ on Pixabay

Article: Quantifying Human-Induced Dynamic and Thermodynamic Contributions to Severe Cold Outbreaks Like November 2019 in the Eastern United States
Authors: C. Zhou, A. Dai, J. Wang, and D. Chen

Questions about extreme cold outbreaks have been featured in the U.S. news recently, as a majority of the country experienced record-breaking cold temperatures during the week of February 8, 2021. Was this extreme cold related to climate change? Will we see more of these events in the future? As Texans faced extensive blackouts due to issues with electricity generation and transmission because of the cold, meteorologists and news reporters tried to answer these questions as best they could. But what does the latest climate science say about the link, if any, between extreme cold outbreaks and climate change?

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Prehistoric Microbial Meals Found in the Australian Outback

Featured Image: Rock fracture from the Dresser Formation, Australia. Fluid inclusions are trapped in the white stripes. Image courtesy Ser Amantio di Nicolao, used with permission.

Paper: Ingredients for microbial life preserved in 3.5 billion-year-old fluid inclusions

Authors: Helge Mißbach, Jan-Peter Duda, Alfons M. van den Kerkhof, Volker Lüders, Andreas Pack, Joachim Reitner, Volker Thiel

Just a few weeks ago NASA made a historic landing of the Perseverance rover on Mars.  This rover symbolizes our human drive for exploration and the need to find the origins of life to answer the big question—are we alone in the universe?  In addition to extraterrestrial investigation and research, we can address this fundamental question here on our own planet by digging into extreme environments that are analogs for ancient Earth or other planets.  These unusual environments, such as hydrothermal vents in our deepest oceans, boiling hot springs in Yellowstone, and prehistoric lakes in South America, can give us glimpses of ancient information and clues about to the ingredients of life.  By discovering our own origins of life, we can begin to understand how it may evolve on other planets.

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Hunting for Antibiotics in Caves

Featured Image courtesy Doronenko and Wikimedia Commons

Paper: High-Throughput Sequencing Analysis of the Actinobacterial Spatial Diversity in Moonmilk Deposits.

Authors: Marta Maciejewska , Magdalena Całusińska, Luc Cornet, Delphine Adam, Igor S. Pessi, Sandrine Malchair, Philippe Delfosse, Denis Baurain, Hazel A. Barton, Monique Carnol and Sébastien Rigali

Do you ever think about the microbes around you when you go caving? Me neither, but a team of scientists from Belgium did. 

Actinobacteria are found in many places around the world, including volcanic terrains and ice caves. They are of particular importance to cave ecosystems and structure since the formation of speleothems (cave formations) like moon milk is thought to be aided by Actinobacteria. These microbes are known for their ability to produce filaments and aid calcium carbonate deposition and precipitation, which could be important for the mineral deposition that forms speleothems. 

Moonmilk deposits from Bergmilchkammer cave (1862/20), courtesy Doronenko and Wikimedia Commons

Despite the importance of microbes in caves, our understanding of microbial communities and spatial distribution within a cave is still fairly limited, i.e. we still don’t know which microbes dominate cave formations and where they live. An international team of scientists set out to answer these questions using three speleothems in the Grotte des Collemboles (English: Springtails’ Cave) in Belgium. Using sterile scalpels, the team scraped soft moonmilk deposits from the walls of the cave into tubes to understand whether different speleothems in the same cave have different bacterial communities.

Using high-throughput DNA sequencing, they found that all the moonmilk deposits had over 700 species in common but distinct communities of bacteria. At least 10% of the species on a particular speleothem were unique to it, and they identified over 4,000 species in total. Actinobacteria was the second-most abundant group (after Proteobacteria) across deposits and many Actinobacterial groups like Nocardia, Pseudonocardia and Streptomyces were found at every speleothem.

Within Actinobacteria, the genus Streptomyces showed the highest diversity (19 species) across all sites even though they only comprised 3% of the actinobacterial community. Interestingly, the team could only grow 5 of these Streptomyces in the lab, which reinforces the significant obstacles to culturing microorganisms still faced by microbiologists.

Streptomyces coelicolor colonies, courtesy Norwich Research Park Image Library

Streptomyces are already a prodigious source of antibiotics and other biologically important compounds, but could these speleothem communities be a source of novel antibiotic compounds? The answer might be worth exploring, given the diversity of Streptomyces found in just this one cave but also the emerging roles of other Actinobacteria in antibiotic production.

The difficulty of growing in situ the bacteria we find in cave formations might complicate our ability to study the compounds they produce, but such adventures could still offer fascinating insights into the microbial inhabitants of caves and how they help bind mineral formations together. The next time you go caving, hopefully you’ll think about the Actinobacteria that surround you!

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Hunting for Antibiotics in Caves by Janani Hariharan is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Tiny Crystals, Big Story: Time capsules from the Early Mars

Featured Image: Zircon grain under the Scanning Electron Microscope (SEM). Image used with permission from Wikipedia (Emmanuel Roquette).

Article: The internal structure and geodynamics of Mars inferred from a 4.2-Gyr zircon record.

Authors: Maria M. Costa, Ninna K. Jensen, Laura C. Bouvier, James N. Connelly, Takashi Mikouchi, Matthew S. A. Horstwood, Jussi-Petteri Suuronen, Frédéric Moynier, Zhengbin Deng, Arnaud Agranier, Laure A. J. Martin, Tim E. Johnson, Alexander A. Nemchin, and Martin Bizzarro

While sitting in Geology 101 studying the geological time scale, most of us have gone through this experience where we imagined ourselves going back in time; visualizing mammoths passing by, dinosaurs hunting and fighting. But all these pictures start to become hazy and unclear when we reach close to 4 billion years. It is the time for which we have no rock records, and this is where zircons or what I would like to call “tiny survivors” comes in.

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