Ocean's Plastics Offer a Floating Fortress to Microbes

Steady streams of tiny plastic pieces making their way into the ocean give microbial squatters a place to take up residence

Steady streams of tiny plastic pieces making their way into the ocean give microbial squatters a place to take up residence. Each plastic home comes equipped with a solid surface to live on in an otherwise watery world. These floating synthetic dwellings and their microbial inhabitants have a name: the plastisphere.

Microbes of the plastisphere live in waters from Australia to Europe. They differ by location, are as varied as the plastic they live on and can be a tasty food option for other creatures. What impact — good or bad — the microbe-covered plastic has on the oceans is still in question. Early hints suggest that there may be climate effects and unexpected movement of harmful microbes or other creatures to new destinations. Each study sparks new ideas and new theories.

“This is an opportunity to learn about the ocean from a big experiment that has already been put in place by humans,” says marine chemist Tracy Mincer of the Woods Hole Oceanographic Institution in Massachusetts. 

As the plastic multiplies

Plastic is everywhere. Finding it polluting the world’s oceans has been a worrisome reality for years. But a discovery more than four decades ago shocked a pair of Woods Hole researchers.

In 1972, scientists were trawling the surface of the Sargasso Sea in the North Atlantic Ocean to collect Sargassum , a brown algae seaweed. The researchers’ interest was diverted, however, by an unexpected catch: tiny plastic particles.

Repeated net tows caught more plastic. The researchers calculated an abundance of 3,500 small plastic pieces per square kilometer, and were left thinking about the future. “The increasing production of plastics … will probably lead to greater concentrations on the sea surface,” the researchers wrote in  Science .

More recent estimates put the amount of plastic floating in the world’s oceans at more than 5.25 trillion pieces, weighing more than 268,000 metric tons ( SN: 1/24/15, p. 4 ). That translates to as much as 100,000 pieces per square kilometer in some areas of the ocean.

In a few places, the concentration of plastic and other trash has earned a nickname or two. In the North Pacific Ocean, for example, the expanse between Japan and the U.S. western coast is variously known as the “great Pacific garbage patch” or the “Pacific trash vortex.”

These floating areas of debris aren’t visible to satellites, however. The ocean still looks blue because most of the junk is barely visible tiny bits of plastic. 

These microplastics are no bigger than 5 millimeters across and come from many sources. Some are broken bits of larger plastic pieces. Others, such as synthetic fibers from clothing and plastic beads from toothpastes and face washes, escape cleaning filters at wastewater treatment plants and end up in the ocean.

Source: Science News

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