The Chesapeake Bay Is Turning Into Plastic Soup
The presence of microplastics—from broken-up containers to ingredients in bathroom products—has been established in four Bay tributaries by researchers at the University of Maryland, NOAA, and elsewhere. “Microplastics were found in all but one of 60 samples, with concentrations ranging over 3 orders of magnitude (<1.0 to >560 g/km2),” they write in Environmental Science and Technology. “Concentrations demonstrated statistically significant positive correlations with population density and proportion of urban/suburban development within watersheds.”According to my primitive math, if the Bay averages 10 meters in depth (the commonly bandied number) a km2 is, get this, ten million cubic meters, or 10 billion liters. At the high concentration of 560 g/km2, that's a concentration of 5 parts in 10 billion or 0.5 parts per billion (ppb, ug/l, whatever). About the concentration of say, copper (which really is poison).
One can deduce that with more growth around Baltimore and Washington, D.C., we can expect to see yet more microplastics. See, and maybe eat, too, as scientists recently discovered the stuff’s being consumed by plankton and passed up the food chain. That’s bad news for marine animals, which can starve on the nutrientless substances or die of stomach obstructions, and possibly for humans, as plastics leach chemicals into fish with unknown impacts on our health. (They might also affect that treasured Chesapeake delicacy, blue crabs, as crabs both eat and breathe in microplastics.)But plastics are notoriously inert chemically. Most break down very slowly in sunlight. We don't worry much about kids eating plastic, except when it presents a possible choking hazards. As for microplastics presenting a choking hazard to filter feeding animals, have you ever seen some of the bizarre, spiked shapes that many marine algae have? Certainly if filter feeders can avoid, or even better yet successfully consume such items, a few small pieces of plastic mixed in will be no great threat.
The Chesapeake Bay Program interviewed the study’s lead author, the University of Maryland’s Lance Yonkos, to determine the sources and ramifications of microplastics. Here’s an excerpt:
“We have many of the prime sources for creating and introducing microplastics to aquatic environments,” Yonkos said. Roads are a main contributor because they promote physical degradation of plastics and provide easy transport via storm drains to Bay tributaries. Yonkos listed wastewater treatment plant effluent and substantial shipping traffic.
As plastic fragments become smaller, a greater number of animals are able to swallow them—as exemplified by the recent case of a whale killed by a shard from a DVD case. When these materials break down enough reach the level of microplastics, even filter feeders like oysters can consume them….
But, the science isn’t clear yet on whether microplastics represent a serious environmental or human health concern.