Featured Image: African Savannah elephants have been long-renowned for their importance in shaping the land they live on. Copyright: CC BY-SA 4.0, via wikimedia commons.
Authors: Christopher E. Gordon, Michelle Greve, Michelle Henley, Anka Bedetti, Paul Allin & Jens-Christian Svenning
Elephants have an enormous impact on their surrounding environment, particularly through their impact on the openness of the savannah, earning them a reputation as “ecosystem engineers”. Species like elephants, with important influences on the landscape around them, are being studied in efforts to rewild parts of the planet; restoring ecosystems in ways that they can sustain themselves. A recent paper by Gordon et al. explores elephant rewilding across South Africa and assesses its effect on vegetation and animal species across various nature reserves and time spans dating back to 1927.
Earth’s oceans not only harbour a multitude of organisms, they are also a major carbon sink, compensating the increased production of carbon by humans and thus slowing down climate change. But could hydrothermal vents be another source of carbon in the oceans themselves?
A lot of the carbon that is produced on land by organisms and industry is transported into the oceans by rivers and wind. Black carbon (or soot), which is for example produced by incomplete burning of fossil fuels, can be stored in the oceans and remain inaccessible for long periods of time (several thousand years). But is all the stored black carbon coming from land sources? Although scientists already had some hints that not all dissolved black carbon (DBC) in the oceans comes from the land, a reliable evidence for a DBC source within the oceans remained elusive. The research from a group from Japan was able to shine new light on this question by looking at hydrothermal vents in the Pacific Ocean.
Authors: Sofia Baliña, María Laura Sánchez, Irina Izaguirre, Paul A. del Giorgio (2023)
Imagine some of the most dynamic, ecologically important lakes in the world…. you are picturing a deep, wide lake, not something knee deep and murky, or so full of aquatic plants you can’t see the bottom, right? Well, perhaps you should; while they don’t always make the most inviting swimming holes, small, shallow lakes have an outsized importance in the cycling of carbon and other nutrients through the landscape.
Shallow depths tend to lead to warmer temperatures and more concentrated growth of algae and aquatic plants, not always the most desirable features for recreation. But what these lakes might lack aesthetically, they make up for with a massive contribution to the global carbon cycle. Combine the abundance of small lakes with a tendency for frequent mixing of the water column, and high rates of organic input from the surrounding watershed and small lakes pack a big punch in terms of cycling nutrients, including carbon, through pathways in both the water and lake bottom sediments.
These carbon cycling power houses are tricky to pin down because they can operate in what scientists call two different ‘stable states’: a murky, turbid state, dominated by algal growth that blocks the sunlight from reaching the bottom, and a clearwater state where plants anchored in the lake bottom sediments are dominant. A number of natural events, including floods, droughts, or changes in surrounding vegetation can lead to a ‘flip’ between states. Human activity can lead to a ‘flip’ as well, for example, in the Pampean Plains of Argentina, agricultural practices have added excess nutrients to the system, which tends to push lakes toward the murky, turbid state. The two lake states not only look different from the surface, but also have important differences in rates of photosynthesis, burial of organic material, and circulation in the water.
Knowing the importance of small lakes to global carbon cycling, a team in Argentina did a detailed investigation on how the different states impact carbon cycling and green house gas emissions. By monitoring sets of turbid and clear shallow lakes in the Pampean Plains over the course of a year, they found important seasonal differences in rates of carbon dioxide (CO2) diffusion into and out of water column, and in the flux of methane (CH4) from lake bottom sediments.
Through monitoring instrumentation suspended in the air above the lakes, as well as measurements taken in the water and sediments, researchers were able to observe weather-driven seasonal changes. The biggest differences were between winter and spring: cold, clear lakes tended to act as CO2 source. When the lakes warmed up, they started to move gas from the water into the atmosphere and became carbon sinks, while turbid lakes did the opposite.
Figure 3 from Baliña et al. (2022) showing the different pathways and relative ratios for carbon flow in clear-water, vegetated lakes (on the left) compared to more green, or turbid, lakes with heavy algal growth on the right. In total, the total greenhouse gas emissions (or CO2 equivalents) for both lake states was similar, but came from different pathways in the lake.
Over an annual cycle, clear lakes had as much as 5 times the CO2 emissions to the atmosphere as compared to turbid lakes, mainly attributed to the vegetation. Turbid lakes, however, had a higher annual emission of CH4. On balance, the two groups of lakes had roughly the same total contribution to green house gas fluxes, but the seasonal variability and differences in carbon pathway are important to understand as we continue to learn more about these dynamic ecosystems and how they change over time.
On the 28th January 2023 NASA’s MSL Curiosity rover team confirmed the rock ‘Cacao’ as an iron-nickle (Fe-Ni) meteorite on the surface of Mars. Curiosity captured images of a silvery-grey rock, very distinctive among the beige-red sedimentary landscape it is currently exploring. Cacao is a ‘float’ rock, meaning is it not embedded within the bedrock and is not where it formed. Float rocks are common on Mars, but many can be traced back to the upper ledges of slopes they have fallen from, or as ejecta from a nearby impact. Cacao has joined a special group of float rocks that are distinct in appearance, genetic composition, and origin.
Authors: Ceth W. Parker, John M. Senko, Augusto S. Auler, Ira D. Sasowsky, Frederik Schulz, Tanja Woyke, Hazel A. Barton
Consider this: microscopic creatures literally moving tons of rock before your very eyes. It seems too fantastical, but maybe not if you’re in the Brazilian tropics. In new work, scientists have detailed these stealthy and microscopic processes, naming a new cave generation pathway called exothenic biospeleogenesis, or “behind-wall life-created” caves.
