Are We Forcing Seabed Microbes to Produce More Greenhouse Gases?

You have a headache and buy a pack of painkillers. Before taking one, you skim the package insert and discover a new side effect listed: Global warming.

— That might sound far-fetched, but there would actually be some truth to it. Our coastal environments are receiving a constant stream of man-made chemicals that may be influencing methane production, says Tetyana Gilevska, a postdoctoral researcher at the Department of Biology.

She is an environmental chemist with a special interest in what happens to different organic pollutants that pass through wastewater treatment plants and end up in our coastal marine environments.

Caffeine and Cosmetics

These pollutants include substances from pharmaceuticals, pesticides, cosmetics, and personal care products, which enter the coastal environment via wastewater. There, they sink to the bottom and settle in the sediment—potentially altering microbial processes in ways that could increase methane emissions.

Also caffeine – which we consume daily in coffee, tea and soft drinks - follows the same path to coastal sediments. According to Tetyana Gilevska, we need to understand its potential influence on methane production.

- In lab experiments with caffeine and the pharmaceutical compound naproxen (a common pain-relieving and anti-inflammatory drug), colleagues and I observed microbial degradation processes that resulted in methane production, she explains.

This work was done with professor Amelia-Elena Rotaru from Department of Biology at SDU and associate professor Stefano Bonaglia from the University of Gothenburg.

Based on her caffeine- and naproxen findings, Gilevska’s research ambition is to investigate more organic pollutants and more types of microbes to get a clearer picture of how increased pollution affects sediment microbes’ methane production.

There is considerable scientific interest in how coastal environments contribute methane emissions to the atmosphere, and what factors influence this. Some researchers investigate whether increased nutrient input leads to higher methane production, while others focus on fluctuations in oxygen depletion and water depth.

— No one has yet thoroughly explored the potential link between organic pollutants and increased methane production, but I believe we should, says Tetyana Gilevska.

How Widespread is This Phenomenon?

She acknowledges that the task may seem overwhelming from the outset: There are thousands of organic pollutants that may be exposed to many different environmental conditions (temperature, oxygen levels, light, etc.) in aquatic environments. At the same time, there are countless microbial species with varying appetites for different substances under different conditions.

— The number of possible combinations is vast. But we need to find out how widespread this phenomenon is and whether it's relevant to our handling of the climate crisis, she says.

Not long ago, scientists believed that methane-producing microbes could only produce methane in a few different ways. Today, dozens of methanogenic pathways are known, and the list continues to grow.

Painkillers and UV Filters

The big question is whether these pathways have always existed and we just didn’t know about them—or whether methane-producing microbes have developed new ways of making methane in recent times because they’ve been exposed to a rapidly growing range of man-made organic pollutants.

— That's a great question! We don’t know. Microbial communities demonstrate remarkable metabolic flexibility when exposed to novel organic compounds. Under persistent pollutant exposure, they can develop biochemical pathways - including potentially new methanogenic routes we haven't previously observed, explains Gilevska.

- As chemical pollution becomes increasingly prevalent, we need clear answers, she concludes. Which compounds influence methane production, through what biological pathways, and to what degree? Understanding these factors is crucial for properly evaluating this potential climate impact.

Among the common organic pollutants that are washed into the sea with wastewater, in addition to naproxen and caffeine, are ibuprofen from painkillers and UV filters from sunscreen, which are rinsed off our bodies when we swim.