Rivers of plastic are hazardous to fish

Posted on October 15, 2015

The annual global production of plastics is close to 30 million tonnes and plastic items are one of the most ubiquitous types of pollutant. Although much plastic debris is transported to the oceans by way of freshwater streams, there are very few estimates of plastic loads in rivers. A recent study carried out on the Danube, the world’s most international river basin with flows from 19 countries, is the first on plastic transport in a large river. A section of the Danube near Vienna was surveyed in 2010 and 2012, using conical driftnets with 500 µm mesh that were fixed on the riverbed and sampled the top 50 cm of the water column. The nets retained spherules, pellets and flakes (precursors of plastic products that enter rivers from processing or distribution sites) and other plastic fragments <2 mm to 20 mm in diameter. The mean plastic load was 317 items per 1000 m3, with the Black Sea receiving over 1500 t from the Danube each year. Since the plastic load was high relative to the density of fish larvae (275 / 1000 m3), and since small fish confuse plastic particles with planktonic food items, plastic pollution is likely to have an adverse effect on river ecology.

Reference: Lechner, A. et al. 2014. The Danube so colourful: A potpourri of plastic litter outnumbers fish larvae in Europe’s second largest river. Environmental Pollution 188, 177-181. http://www.sciencedirect.com/science/article/pii/S0269749114000475