[The researchers] noticed many of their pieces of [plastic marine] debris sported surface pits around two microns across. Such pits are about the size of a bacterial cell. Closer examination showed that some of these pits did, indeed, contain bacteria, […].
(US, colloquial, mildly vulgar, short for piece of crap/piece of shit) A shoddy or worthlessobject (usually applied to consumer products like vehicles or appliances).
Ugh, my new computer is such a piece. I'm taking it back to the store tomorrow.