The role of hadal zones in the long-term fate of marine microplastics: Identification of microplastics in the deep sea of the Kuril-Kamchatka Trench, Northwest Pacific (Deep-MiPoll)

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This project`s main aim is the qualitative and quantitative identification of microplastic (MP) contamination of the deep sea, to gain a better insight into the actual extent of global marine MP pollution and its distribution. In the Kuril-Kamchatka Trench, NW Pacific, sediment samples were taken from depths ranging from 5146 m to 9540 m using a Multi Corer. Sampling of plankton samples was conducted by a Multi Net and reached a maximum depth of 5900 m. Additionally, bigger items of anthropogenic litter were separated from bottom trawling samples. These sample records are worldwide unique in the context of MP research and will provide data about the contamination of hadal zones for the very first time.Sample preparation will be conducted through a plastic-preserving method using Fenton`s reagent to oxidize organic matter and a subsequent density separation to separate MP from the sediments. Analyses will be performed by state-of-the-art micro-Fourier Transform Infrared spectroscopy, which allows a precise and objective determination of the plastic polymers and thus, the identification of possible pollution sources. The connection with biological and environmental parameters will place the results in a broader context and examine possible implications.Plastic contamination is one of the most urgent manmade threats for natural environments. The oceans are affected particularly, followed by multifaceted negative effects on ecosystems and single organisms. Once introduced, plastic is very persistent, since there is no significant biological or chemical degradation. Instead, plastics merely tend to be fragmented, leading to steadily rising numbers of fragments of decreasing size, the so-called MP (<500 µm). It has been ascertained that a substantial fraction sinks to the seabed. Thus, the seabed must be presumed as a hot spot of MP accumulation and its deepest parts, the hadal zones, as a final sink for marine MP. This project will contribute to verify the abundance and composition of MP in the deep sea. Furthermore, investigations on spatial differentiation of abundance and composition with depth and through the sediments will be performed. The seas around Japan are exceedingly polluted with pelagic plastic, Deep-MiPoll will investigate a possible causal link between occurrences of MP in the water column and in hadal sediments.In previous studies on MP in the deep sea, sampling reached around 5500 m, hence initial data for deep abyssal and hadal zones will be generated for the first time. This will constitute a big step forward in MP investigations and help to clarify the contribution of vertical propagation for general spatio-temporal distribution and the role of the deep sea in the long-term fate of marine MP. The Deep-MiPoll project will investigate MP in deep-sea samples using spectroscopic analyzing methods systematically for the very first time, and thus, provide highly novel and reliable data about the MP pollution of deep-sea ecosystems.