![]() ![]() In 2012, sampling started 2 h before sunset (according to ephemeris) and was continued in hourly intervals until midnight. In 2010, we sampled circadian (24 h) periods with hourly intervals between single sample events. In this volume-reducing approach, the filtered sample (containing plastics, fish larvae, organic debris and other items) is collected in a jar attached to the net-end and can be taken to laboratory for further processing.ĭuplicates (2010) and triplicates (2012) of driftnets were simultaneously exposed at three (2010) to four (2012) sampling stations along both river margins with maximum distances of 1 km between the single stations and 25 m between the shoreline and driftnets. A flowmeter (2030R, General Oceanics ®, Miami) was attached to the lower third of each net entrance to measure the volume of filtered water. The mesh size we used is in the range of other studies that quantified suspended plastics (reviewed in Hidalgo-Ruz et al., 2013). Nets covered 60% of the water column in more than 75% of all cases. Briefly, we utilized stationary conical driftnets (0.5 m diameter, 1.5 m long, 500 μm mesh) that were fixed to iron rods driven into the riverbed and sampled the top 0.5 m of the water column. ![]() The sampling procedure has been accurately described elsewhere ( Lechner et al., 2013b). Inputs from land-based sources have gained less attention but are supposed to be high, especially via the Danube River System ( Lebreton et al., 2012). Beside eutrophication, the vulnerable ecosystems of this continental water face an increasing threat of plastic litter pollution ( Topcu et al., 2013). As the main tributary (input of 6444 m 3 s −1 at mean flow) and major nutrient pathway, the Danube directly affects the Black Sea ( BSC, 2009). ![]() Featuring the world's most international river basin (19 countries, 800.000 km 2, 81 million people), the Danube is a special case study regarding conservation and management issues ( Sommerwerk et al., 2009). Here, the average river width is 350 m and the discharge at mean flow is 1930 m 3 s −1. All sampling sites were situated within the “Danube Alluvial Zone National Park” which preserves the last remaining major wetlands environment in central Europe ( ). The study was conducted in a free flowing stretch of the Austrian Danube between Vienna and Bratislava. All sacrificed individuals were handled according to applicable regulations and used for comprehensive analysis ( Lechner et al., 2013b). The whole study was embedded in a scientific project that highlights larval dispersal and the conservation of riverine fish populations. ![]() To our knowledge, this is the first report on plastic transport in a large river. Finally we give a rough estimate of the input of plastic litter via the River Danube into the Black Sea. Adverse health effects may arise when small fish confuse plastic particles with food items (zooplankton, fish eggs) and ingest them ( Carpenter et al., 1972). In a second step we compare plastic abundance and plastic mass in the river with those of ichthyoplankton (drifting fish larvae and juveniles). The main aim of the study was to categorize and to quantify drifting plastic items. In this article, we present results from a two-year (2010, 2012) survey on plastic litter transport in Europe's second largest river, the Danube. Realistic estimations of the plastic flow from rivers to oceans are very important in helping to raise the awareness of the sources of plastic debris and ultimately to drive measures to reduce it. Nevertheless, quantifications of plastic loads in rivers found in primary literature are minimal ( Moore et al., 2011). A significant portion of the terrestrial plastic is transported to the seas by rivers. Marine plastics originate from ship or land-based sources ( Coe and Rogers, 1997) with the latter to be of greater relevance ( Andrady, 2011). Although accumulation of plastic in the ocean is prevalent, there is scarce data on plastic inputs in the oceans ( Law et al., 2010). Marine systems are sinks for pre- and post-consumer plastic and the multifaceted negative impacts of plastic pollution on wildlife (reviewed in Cole et al., 2011 Derraik, 2002 Oehlmann et al., 2009) as well as several aspects of debris composition, distribution and abundance have been described here (reviewed in Ryan et al., 2009). The annual global production of the organic polymer has rapidly increased from 1.7 to 280 million tonnes within the last 60 years ( Plastics Europe, 2012) resulting in the accumulation of plastic litter in virtually all habitats ( Browne et al., 2011). Plastic, the lightweight and long-lived material, has become a serious environmental hazard ( Thompson et al., 2009). ![]()
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