Reactive Oxygen-Containing Molecules Have a Significant Impact on Mineralization in Sandflats

According to a new study published in Nature Communications, reactive oxygen species--highly reactive molecules containing oxygen--have a significant impact on mineralization processes in tidal sandflats. As a result, their research is critical for understanding marine carbon cycling.

The Wadden Sea, which stretches 500 kilometers along the North Sea coasts of Denmark, Germany, and the Netherlands, is mostly made up of intertidal permeable sediments. The seafloor that is flushed by seawater during tide changes. It is frequented by seabirds, marine mammals, and tourists.

However, this highly dynamic environment is also home to a plethora of microbes. They process carbon and nutrients from seawater and fluvial inflows, transforming the sand into an important site for organic matter remineralization and a massive purifying filter.

An Ideal Location For ROS Production

The sediments' frequent fluctuation between oxic and anoxic conditions (at high and low tide, respectively) makes them an ideal location for producing reactive oxygen species (ROS). ROS are oxygen-containing molecules with high chemical activity, as per Phys.org.

ROS play a multifaceted role in the environment: they can be harmful to organisms and damage cell components, but they can also be beneficial to microbial growth.

ROS are very important agents in the transformation and cycling of carbon and other substances in the environment due to their high activity and can thus have a significant impact on the functioning of ecosystems.

Nonetheless, they are understudied in many habitats, including the Wadden Sea's sandy flats.

A team of scientists from Bremen's Max Planck Institute for Marine Microbiology studied ROS in a sandflat called Janssand in the German Wadden Sea off the island of Spiekeroog.

Olivia Bourceau, Marit van Erk, and their Microsensor Group colleagues investigated the ROS hydrogen peroxide.

Microbial Activity Is Influenced By Hydrogen Peroxide

Indeed, the team Bourceau and van Erk led discovered high levels of hydrogen peroxide in the intertidal sands.

"We discovered a delicate balance between hydrogen peroxide production and degradation," says co-author van Erk, as per Eurekalert.

In experiments, the scientists altered the oxygen input or removed hydrogen peroxide, which had a significant impact on the sand-dwelling microbes.

ROS inhibited the microorganisms in the sand, so removing it increased microbial activity.

The amount of ROS naturally present in the sands significantly reduced the rates of the two main mineralization processes, aerobic respiration, and sulfate reduction.

Carbon And Nutrient Cycling Rely On It

Elevated ROS levels are to be expected, especially during disturbance events and at oxic-anoxic interfaces, both of which are common in intertidal permeable sediments.

Because of the high rates of carbon and nitrogen remineralization, these sediments serve as massive biocatalytic filters.

Any changes in ROS concentrations may thus have a direct impact on the effectiveness of sands as filters and the functioning of shallow water ecosystems.

As a result, ROS may play a significant and underappreciated role in the biogeochemistry of dynamic coastal sediments.

They can conclude from Bourceau's findings that ROS has the potential to significantly impact carbon cycling in sediments.

Understanding carbon cycling controls is critical for studying eutrophication and the impact of human activity on coastal systems.