Polystyrene consists of tiny plastic grains pressed together into a block. These large blocks of foam can float and support a dock because of their trapped air. Larger flecks of foam can also float and be moved by wind and waves. However, once smaller particles break off, their behaviour can change. Their small size, large surface area, and interactions with algae and bacteria can cause them to settle into sediment.
Compared with other plastics, exposed polystyrene foam can shed easily, as it is weakened by sunlight, waves, ice and boat disturbance. Once the surface is damaged, small pieces can fragment. These particles may not remain floating for long, quickly sinking into the sediment around docks, out of reach of surface water samples.
See the photo showing the polystyrene grains stirred up like a snow globe. The particles are mostly found in the sediment around the docks. This suggests that pollution from exposed docks concentrates nearby and affects the dock owner’s shoreline and nearby neighbours. Is it a health concern if grandkids stir up sediment? Scientists do not yet know.
