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!

Creative Commons License

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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Water in the rocky layer cake beneath us

Konza Prairie Biological Station

Featured Image: Konza Prairie near Manhattan, Kansas, USA. Credit: David Litwin.

Paper: Toward a new conceptual model for groundwater flow in merokarst systems: Insights from multiple geophysical approaches.

Authors: Sullivan, P. L., Zhang, C., Behm, M., Zhang, F., & Macpherson, G. L.

The dissolution of limestone by atmospheric water forms a set of recognizable features collectively known as karst: enormous caves with stalactites and stalagmites, sinkholes, chasms, and narrow, towering  columns of rock. The hydrology of karst landscapes is often incredibly complex, as water can flow rapidly through dissolution-formed conduits below ground, and topography offers fewer clues to groundwater flow than in most other landscapes. While dramatic karstic landscapes have received a lot of scientific attention, even smaller limestone units can host karst features that affect hydrology.

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Cracking the code of the caramel crust

Featured image: a view of the Calico Basin in the eastern part of the Mojave Desert. Photo by Fred Morledge, CC BY-SA 2.5, via Wikimedia Commons.

Paper: Thin crème brûlée rheological structure for the Eastern California Shear Zone
Authors: Shaozhuo Liu, Zheng-Kang Shen, Roland Bürgmann, & Sigurjón Jónsson

A recent paper by Liu and colleagues aims to answer a fundamental question in geodynamics: are Earth’s tectonic plates more like a jelly sandwich, or a crème brûlée? It may sound silly, but these two models for crustal strength describe how tectonic plates might respond to stress changes due to earthquakes.

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Himalayan Glaciers: A Store House of Picturesque Landforms

Himalayan Glaciers A Store House of Picturesque Landform

Featured image: Thajwas Glacier from Wikipedia under CC BY-SA 4.0.

Paper: Glacial-geomorphic study of the Thajwas glacier valley, Kashmir Himalayas, India

Authors: Reyaz Ahmad Dar, Omar Jaan, Khalid Omar Murtaza, Shakil Ahmad Romshoo

Glacial retreat caused by climate change is an urgent problem around the globe, as glaciers which hold 68.7% of our freshwater sources are rapidly melting. There are several regions around the world where snow covers the whole region almost all the year round. These places are not only a place for tourist destinations but are also covered with various landscape features which carry vital information related to past glacial activities, including both the advancement and the retreat of glaciers that occurred during the Late Glacial Maximum.

In a new research study on Thajwas Glacial Valley in Sonamarg which is located in the upper reaches of the Indus River in Kashmir Himalayas, the researchers studied the available glacial-geomorphic features of the region. The geomorphic landforms shaped by the glaciers provide scenic landscape beauty to the region. The reconstruction of palaeo-glacial features of the region is assisted by the development of different landforms in the valley such as cirques, characterized as amphitheatre shaped valleys, glacial troughs or U-shaped valleys, and terminal moraines which forms at the end of the glaciers.

The researchers developed a glacial-geomorphic map featuring all the available glacial landforms features of the valley as well as the behaviour of the past glaciers with the help of input from both field observations and geomorphic information collected from satellite imagery and Google Earth. The major bedrock lithological formation of the region consists of Panjal Volcanics composed of basaltic rocks interposed with pyroclastic materials produced by volcanic activities. Various glacial landform features have been mapped with ground-based observations in the area. Small-scale features such as erratic boulders, kettle holes, glacial meltwater streams, etc. have also been mapped for the region using images from Google Earth. These glacial landforms vary in size from one meter to more than hundreds of meters.

A schematic of glacial landforms. Source: Wikimedia

In the Kashmir Himalayas, the process of glaciation has resulted in complex topographical features as an outcome of landscape evolution. Evidences found for the advancement of glaciers in the Great Himalayan mountain range near the Kashmir Valley. This research suggests that the glaciers in the Kashmir Himalayan region are showing signs of depletion as well as recession as an impact of recent warming observed in the region. The satellite data revealed the expansion of Thajwas Valley at the expense of retreating cirques of tributary glaciers. The presence of steep slopes on the north-eastern side is evidence of fluvial incision i.e., the process of narrow erosion by a river far from its base level, with slight glacial erosion; on the other hand, the gentle slope found on the south-western side is a result of the retreat of the cirque due to erosion.

During the Late Quaternary period, the Valley of Kashmir has experienced cycles of glacial and interglacial activities. Global cooling led to the growth of the glaciers together with high rates of erosion which shaped the landscape of the region. Serrate ridge present in the area indicates a gradual lowering of the ice levels. Recessional moraines, kettle hole and outwash plains observed in the region indicates the deglaciation process owing to climate change. The region has experienced substantial glacial and climatic fluctuations during the Late Quaternary period. Using area scaling method the researchers estimated that the Thajwas glacier has lost 88% of its volume after its last advancement. Presently, the Thajwas glacier is estimated to have lost 81% of its surface area.

Our lives are indirectly dependent on the glaciers, as they control the climatic balance and other geographical phenomena occurring on the earth. Research into the retreat of these glaciers is imperative to understand how we can preserve this indispensable natural resource for a sustainable life.

Himalayan Glaciers: A Store House of Picturesque Landforms by Shilpa Saha is licensed under CC BY-SA 4.0 

There’s microplastics in the Arctic, and we can probably blame home laundry

Microplastic Thread

Featured image: Microplastic thread courtesy of M.Danny25 on Wikipedia under CC BY-SA 4.0.

Paper: Ross, P.S., Chastain, S., Vassilenko, E. et al. Pervasive distribution of polyester fibres in the Arctic Ocean is driven by Atlantic inputs. Nat Commun 12, 106 (2021). https://doi.org/10.1038/s41467-020-20347-1

The Arctic is full of plastic–polyester fibers to be exact. Peter S. Ross and his team found upwards of forty polyester fibers for every cubic meter of the Arctic Ocean’s surface. Their new study in Nature Communications also revealed that these fibers were more common in the East Arctic, which is fed by the Atlantic Ocean, than the West Arctic. The scientists suggest that the presence of these fibers coupled with their uneven distribution throughout the ocean could be due to an unlikely source: home laundry. 

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Tiny organisms’ race to the bottom of the ocean

Paper: Microbial dynamics of elevated carbon flux in the open ocean’s abyss

Authors: Kirsten Poff, Andy Leu, John Eppley, David Karl and Edward DeLong

Cells from blooms of phytoplankton, or tiny plants, can enhance carbon flux all the way down to the deepest parts of the ocean. The authors of this recent study measured the amount of carbon in sinking particles deep in the ocean at a station near Hawaii. Over the course of three years, scientists identified three time periods of unusually high carbon flux, or transport, at this depth, and found that the organisms that made up the sinking particles were significantly different between high flux events and the rest of the time period. The data showed higher abundances of surface-dwelling microorganisms, including phytoplankton, contributing to these particles during high-flux events.

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