Microplastic in plankton of the North- and Baltic Sea

The environmental pollution with small plastic particles was recognized in the early 70s (Carpenter & Smith 1972). Today these plastics can be found in every marine habitat and are expected to have enormous negative impacts. The smaller the items get through fragmentation the more organisms can feed on them. Zooplankters cannot discriminate while feeding and can absorb POPs or other chemicals adhered to ingested plastics which then have the potential to accumulate in the marine food chain (Cole et al 2013). The term microplastic includes all plastics smaller than 5 mm: These can be released directly as primary microplastic in cosmetics and in form of lost industrial pellets or through fragmentation of larger plastic items (secondary microplastics). Introduced in the environment, plastics cannot be mineralized, but UV- radiation and physical wave actions will lead to the embrittlement and further fragmentation of plastics. Because of this even a direct stop of plastic introduction would lead to an increasing amount of microplastics in the marine environment (Cole et al 2011). Until now nonexistent methods made the detection of microscopic plastics that are smaller than 500 µm impossible and so most of the published studies focus on the visual sorting and determination of samples taken in marine sediments or at the water surface. The new combination of micro- Fourier transform infrared spectroscopy (FTIR) with a focal plane array detector (FPA) is highly promisingly for this (Harrison et al 2012). But to enable this way of analysis a sufficient sample purification is needed that removes all disturbing natural materials without affecting the plastic particles. A method was developed that combines enzymatic digestion with density separation using a ZnCl2 solution. This method allows for the first time the examination of all microscopic plastics of complete plankton samples taken from coastal waters of the German North and Baltic Sea. Although plastic introduction from the high shipping activities and additional landbased sources can be expected in the region, there is little knowledge about large- scale planktonic microplastic concentrations. 28 stations were sampled and the total concentrations of visible and microscopic plastics determined which ranged considerably from 0 to 3.5 items m-3. An outstanding high concentration of 1.3 visible plastics m-3 and the detection of same PE pellets in 2012 and 2013 at the western coast of Denmark could suggest an accumulation zone in this area. A fact that may be supported by the findings of Galgani et al (2000) who found considerably higher plastic concentrations in an 190 large area 200 km away from the Danish coast when examining sedimented macroplastics.