Plastic pollution is already reaching Antarctica and creating an environment favorable to the growth of bacteria, including some with antibiotic-resistant genes.
Antarctica, the most remote, harsh and pristine continent in the world, is not free from marine pollution. Where human activity goes, plastic debris inevitably follows.
What would the first explorers of this icy wilderness think today, upon discovering a continent transformed by permanent fishing activities, research stations, military presence, tourism and all its environmental impacts? Among these, the plastic pollutionwhich created a unique new ecological niche in the ocean.
When plastic debris enters water, it provides surfaces that can be quickly colonized by microbial communities, forming a biofilm. This plastic community is known as plastisphere and poses a serious threat to marine ecosystems, particularly in the cold, little-studied waters of the Southern Ocean.
The plastisphere: an emerging threat
As plastic debris is swept across the ocean, the plastisphere develops through typical ecological succession, eventually becoming a complex and specialized microbial community.
Not only do plastics provide shelter to these microorganisms, they also act as vectors, allowing potentially harmful pathogens such as Vibrio spp., Escherichia coli and bacteria carrying antibiotic resistance genesspread throughout marine environments, reaching remote and untouched areas.
In addition to being a home for microbes, the plastisphere can disrupt the natural balance of ocean life at the microscopic level. These changes do not remain in the water, as they can spread abroadpotentially affecting how the ocean absorbs carbon and produces greenhouse gases. This has consequences for the air we breathe around the world.
However, it’s not all bad news, as bacteria known for their potential to degrade plastics or hydrocarbons – such as Alcanivorax sp., estuary cell sp., Marinobacter sp. and Alteromonas sp. – are often identified on plastics.
A hostile research environment
Currently, we know very little about the plastisphere, especially in the Southern Ocean, where discovering its dynamics is fundamental to understanding its impacts in one of the most remote and vulnerable marine environments on the planet. For this reason, one sought to investigate the abundance and diversity of microbial communities in the Southern Ocean plastisphere, especially after the initial colonization of plastic debris.
Working in Antarctica is not an easy task. Reaching this continent is a challenge and, once there, scientists must face adverse environmental conditions: freezing temperatures, strong winds, icebergs and the constant pressure of a limited time to get your job done. These challenges make every moment on the ground simultaneously demanding and invaluable.
That’s why the new study took a controlled and manageable experiment approach. They set up aquariums with seawater collected near the Spanish research station on Livingston Island in the South Shetlands. Inside, they placed small rounded granules of the three most common types of plastic that pollute the sea – polyethylene, polypropylene and polystyrene. They left us in ambient conditions (around 0 ºC and between 13 – 18 h of sunlight) for 5 weeks, with the aim of recreating the most plausible results in the field.
The colonization of plastics was compared to that of glass, an inert surface. Plastic and glass samples were periodically collected to monitor bacterial colonization.
Plastisphere dynamics in Antarctica
Studying bacteria means making the invisible visible, so they combined several techniques to obtain a best image of the plastisphere. Using scanning electron microscopy, scientists obtained images of biofilms. They combined flow cytometry and bacterial culture to count total cells and colonies, and sequenced the 16S rRNA gene to identify the succession of bacterial colonists.
This meticulous approach revealed that the time was the main factor of change. The microbes quickly colonized the plastic and, in less than two days, bacteria like those of the genus Colwellia were already fixed to the surface, showing a clear progression from initial colonizers to a mature and diverse biofilm, including other genera such as Sulfitobacter, Glaciecola or Lewinella.
These species, although also detected in water, show a clear preference for the social life of a biofilm community. Furthermore, no clear differences were detected between the bacterial communities on plastic and glass, suggesting that any stable surface can welcome these communities.
Although similar processes occur in other oceans, in Antarctica the process appears to be slower. The lower temperatures in the region delay the development of bacteria.
Plastic-eating bacteria?
An important discovery was the presence of Oleispira sp. in polypropylene. This bacteria is a hydrocarbon degrader, which means it belongs to a group of microorganisms capable of decomposing oil and other pollutants.
Its role in the Antarctic plastisphere raises important questions, such as whether this type of bacteria can mitigate the impacts of pollution by plastics. If so, they could be critical to the future of Antarctica and our oceans.
However, there is still much to discover, especially regarding its potential for bioremediation in extreme environments. Understanding these processes could pave the way for innovative strategies to address the growing challenge of plastic waste in marine ecosystems.
