The accumulation of microplastics in our environment is a growing concern. These tiny particles have been found to harm marine life, contaminate food chains, and even enter our own bodies through various pathways. However, predicting where these particles will accumulate and therefore where remediation efforts should focus has been difficult due to the many factors contributing to their dispersal and deposition.

New research from MIT shows that one key factor in determining where microparticles are likely to build up is related to the presence of biofilms. These thin, sticky biopolymer layers are shed by microorganisms and can accumulate on surfaces, including riverbeds or seashores. The study found that when these particles land on sediment infused with biofilms, they are more likely to be resuspended by flowing water and carried away.

The research involved a flow tank with a bottom lined with fine sand, sometimes mixed with biological material simulating natural biofilms. Water mixed with tiny plastic particles was pumped through the tank for three hours, and then the bed surface was photographed under ultraviolet light that caused the plastic particles to fluoresce, allowing a quantitative measurement of their concentration.

The results revealed two different phenomena affecting how much plastic accumulated on the different surfaces. Immediately around the rods simulating above-ground roots, turbulence prevented particle deposition. Additionally, as the amount of simulated biofilms in the sediment bed increased, the accumulation of particles also decreased.

The researchers concluded that the biofilms filled up the spaces between the sand grains, leaving less room for the microparticles to fit in. The particles were more exposed because they penetrated less deeply into the sand grains, making them easier to resuspend and carry away by the flowing water.

This research provides a “nice lens” to offer guidance on where to find microplastic hotspots versus not-so-hot areas. For example, in mangrove ecosystems, microplastics may accumulate preferentially in the outer edges, which tend to be sandy, while the interior zones have sediment with more biofilm. This suggests that the sandy outer regions may be potential hotspots for microplastic accumulation.

The work was supported by Shell International Exploration and Production through the MIT Energy Initiative. While other factors like turbulence or roughness of the bottom surface complicate this, it provides a framework to categorize habitats and prioritize monitoring and protection efforts.

The Hidden Impact of Anoxic Pockets on Sandy Shores

Human activities have dramatically increased nitrogen inputs into coastal seas, leading to a significant amount of this human-derived nitrogen being removed by microorganisms in coastal sands through denitrification. However, research has shown that this process can also occur in oxygenated sands, and scientists from the Max Planck Institute for Marine Microbiology in Bremen, Germany, have now revealed how this happens.

The scientists used a method called microfluidic imaging to visualize the diverse and uneven distribution of microbes and the oxygen dynamics on extremely small scales. “Tens of thousands of microorganisms live on a single grain of sand,” explains Farooq Moin Jalaluddin from the Max Planck Institute for Marine Microbiology. The researchers could show that some microbes consume more oxygen than is resupplied by the surrounding pore water, creating anoxic pockets on the surface of the sand grains.

These anoxic microenvironments have so far been invisible to conventional techniques but have a dramatic effect: “Our estimates based on model simulations show that anaerobic denitrification in these anoxic pockets can account for up to one-third of the total denitrification in oxygenated sands,” says Jalaluddin.

The researchers calculated how relevant this newly researched form of nitrogen removal is on a global scale and found that it could account for up to one-third of total nitrogen loss in silicate shelf sands. Consequently, this denitrification is a substantial sink for anthropogenic nitrogen entering the oceans.

In conclusion, the hidden impact of anoxic pockets on sandy shores has been revealed by scientists, highlighting the importance of these microenvironments in removing nitrogen from coastal seas and emphasizing the need to consider them when assessing the overall nitrogen budget of our planet.

In the arid regions of Namibia, Oman, and Saudi Arabia, researchers have stumbled upon an enigmatic phenomenon that challenges our understanding of geological processes. Unusually small burrows, or tiny tubes, have been discovered in marble and limestone rocks, which are believed to be the result of microorganisms at work. The discovery was made by Professor Cees Passchier from Johannes Gutenberg University Mainz (JGU), who first encountered this phenomenon during his fieldwork in Namibia.

Passchier’s team has found similar structures in Oman and Saudi Arabia, with the tubes forming bands up to ten meters long. These tiny tunnels are not empty; they are filled with a fine powder of clean calcium carbonate, which is believed to be a remnant of the microorganisms’ activities. The researchers speculate that these microbes may have bored the tunnels to access nutrients present in the calcium carbonate, the main component of marble.

The age of these structures is estimated to be around one or two million years old, with Passchier suggesting that they were formed in a slightly more humid climate than the current desert conditions. However, the microorganisms responsible for creating these tubes remain unknown.

This phenomenon has sparked interest among scientists due to its potential implications on the global carbon cycle. The release of carbon through the biological activity of microorganisms could play a significant role in the Earth’s CO2 balance. As Passchier emphasizes, it is essential that the scientific community becomes aware of this discovery and continues to investigate the mystery surrounding these enigmatic tubes.

In conclusion, the discovery of mysterious microorganisms shaping marble and limestone with tiny tubes offers a fascinating glimpse into the complexities of geological processes. While much remains unknown about these structures and their creators, further research may shed light on the secrets hidden within the Earth’s ancient rocks.