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 article reveals that extreme weather events are exacerbating the decline of amphibian populations worldwide. A study from the Institute for Ecology, Evolution, and Diversity analyzed global weather data over 40 years to determine how heat waves, droughts, and cold spells have affected the geographical distribution of more than 7,000 amphibian species.

The results show a clear correlation between increased extreme weather events and deteriorating threat status on the Red List. Dr. Evan Twomey, lead author of the study, explains that amphibians’ dependence on temporary wetlands for breeding makes them vulnerable to droughts and temperature shifts. “Our analyses show the direct connection between the increase in extreme weather events and the decline of amphibian populations,” he states.

Three regions are particularly affected: Europe, where droughts have taken a toll on salamander populations; the Amazon region, where heat waves have impacted frog species; and Madagascar, where both heat waves and droughts have had devastating effects. In Central Europe, future climate projections indicate an increase in drought periods, further exacerbating the situation for native true salamanders.

The study highlights the urgent need for targeted conservation measures to protect threatened amphibian species. These include creating small protected areas and improving wetlands to ensure optimal living conditions. Creating moist retreat sites, such as using pipes or boards, also provides these animals with opportunities to withdraw during dry periods.

As indicators of ecosystem health, the protection of amphibians is paramount for preserving biodiversity. The study’s findings provide essential foundations for adapted conservation strategies in particularly affected regions, emphasizing the importance of taking action to mitigate the devastating impact of extreme weather and habitat loss on amphibian populations.

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.