Hotspots for marine plastics: identifying sources and sinks

The increasing amounts of microplastics in the marine environment is a global problem, and research in the area has surged during the last decade. An important part of the research is in determining the sources and sinks of microplastics in order to minimise the spread of plastic pollution.

MSI is investigating the distribution of microplastics on Australian beaches on a spatial and temporal scale. The aim is to identify hotspots for microplastic sedimentation in beach sand by looking at abundances of microplastics in different locations. We also aim to find links between sources and sinks for microplastics by correlating the abundances of microplastics to potential sources of plastic pollution such as urban environment, tourism and industry, as well as by observing patterns of movement for plastic litter with the help of hydrodynamic modelling. If possible, be will also conduct a chemical analysis of the samples to quantify their metal contents and use that information to connect the plastics to potential sources. The data that will be used in this study originates from the citizen science organisation AUSMAP as well as the Beach database collected by Andrew Short, and potentially additional samples collected to fill in data gaps. AUSMAP has been collecting data on the occurrence of microplastics on beaches around Australia since 2018, and their extensive database holds valuable information about the current distribution of microplastics. The Beach database collected by Andrew Short includes samples of sand from beaches around Australia from between 1987 and 2004. Analysing the microplastic content of these samples and comparing them to the current levels will allow us to study the temporal changes in microplastic abundances on the beaches. This study will be conducted in the area around Sydney, with the possibility for future expansion both concerning the research area and the research method, e.g. by conducting a more extensive chemical analysis.

The study is still in its early stages, and we are just about to start the practical parts. The first step of this study is to identify matching locations between the two datasets that could be used for comparing the changes in microplastic abundance over time. The selection of locations will mainly depend on which beaches there are usable samples from in the Beach database as they represent the historical aspect. Locations that are missing data in the AUSMAP dataset will be sampled if needed. The existing samples from the Beach database will be analysed using a compatible protocol as/with AUSMAP to ensure comparability. Once the locations have been selected, we will analyse physical samples of sand from the Beach database to determine the level of microplastics contamination in the old samples. This data will then be compared with the current data from the AUSMAP sampling to get a picture of the changes in microplastic contamination both over time and in different locations. This data, in combination with a chemical analysis of the samples (Inductive coupled plasma mass spectrometry (ICP-MS)) will then be used to identify sources and sinks for the microplastic contamination and to map out microplastics hotspots in the Sydney coastal area.