Tracy Mincer and Linda Amaral-Zettler report their findings from examining the small bits of plastic floating in the ocean. Using DNA analysis and electron microscopy, they found 50 species of microorganism living there, including a two-level trophic web.
As with many ecosystems, the bottom of the food chain was occupied by things that photosynthesise. These included unicellular algae called diatoms and dinoflagellates, and photosynthetic bacteria known as cyanobacteria. Usually, such creatures swim freely in the ocean. They therefore have to work hard to stay near the surface, where light for photosynthesis is abundant. By hitching a ride on a piece of floating plastic, they can stay near the surface without effort.
They also found evidence that suggests, but does not clearly establish, that bacteria are actively breaking down these energy-rich, petroleum-based substances.