This study estimated the concentration of marine plastics in waters around Australia using surface Neuston and Manta net tows. Data was collected during seven transit voyages aboard Australian vessels. The study undertook three consecutive 15-minute net tows at 57 locations. The 839 marine plastics recorded during the study were predominantly small fragments (i.e. ‘‘microplastics’’, median length = 2.8 mm, mean length = 4.9 mm) resulting from the breakdown of larger objects made of polyethylene and polypropylene (e.g. packaging and fishing items).

Plastic pollution is ubiquitous throughout the marine environment, yet estimates of the global abundance and weight of floating plastics have lacked data, particularly from the Southern Hemisphere and remote regions. Here we report an estimate of the total number of plastic particles and their weight floating in the world’s oceans from 24 expeditions (2007–2013) across all five sub-tropical gyres, coastal Australia, Bay of Bengal and the Mediterranean Sea conducting surface net tows (N5680) and visual survey transects of large plastic debris (N5891). Using an oceanographic model of floating debris dispersal calibrated by our data, and correcting for wind-driven vertical mixing, we estimate a minimum of 5.25 trillion particles weighing 268,940 tons. When comparing between four size classes, two microplastic <4.75 mm and meso- and macroplastic >4.75 mm, a tremendous loss of microplastics is observed from the sea surface compared to expected rates of fragmentation, suggesting there are mechanisms at play that remove <4.75 mm plastic particles from the ocean surface.

This record provides an overview of the NESP Marine and Coastal Hub small-scale study - "Microplastics in South Eastern Australian coastal waters: synthesising current data and identifying key knowledge gaps for the management of plastic pollution". For specific data outputs from this project, please see child records associated with this metadata. Plastic pollution is pervasive in coastal environments globally and in Australia. Due to their small size, microplastics (pieces <5mm) are readily ingested by marine organisms and potentially accumulate across food webs, raising concerns for biota, ecosystem services and human health. Yet, to define guidelines and support policy actions that curb microplastic pollution, managers and decision-makers lack clear, synthesised information on this multifaceted issue, including on occurrence, sources, and pathways of microplastics in coastal and marine environments. This project synthesised current knowledge on microplastics in the coastal waters of South-Eastern Australia (South Australia, Victoria, and New South Wales), identifying key gaps in data, monitoring, and risk assessment. A central output was a compiled database of existing microplastics studies across the study region. Through engagement with stakeholders from government, research, and industry, the project defined shared priorities and barriers to action. Three critical research needs were identified: (1) methodological harmonisation, (2) source and pathway identification, and (3) evidence of ecological risk. Together, the synthesis and stakeholder input set a clear direction for future coordinated research to enable evidence-based management of microplastic pollution across jurisdictions. The work laid the foundation for the development of a Standard Operating Procedure (SOP) for marine microplastics sampling, which was subsequently delivered through NESP Marine and Coastal Hub Project 2.2 (https://www.nespmarinecoastal.edu.au/project/2-2): chapter "Marine sampling field manual for microplastics" in Field Manuals for Marine Sampling to Monitor Australian Waters, Version 3 (https://microplastics-field-manual.github.io). Outputs • Inventory of compiled datasets relating to microplastics in SE Aus waters [spatial dataset] • Final Project Report synthesising the information available on the presence of microplastics in coastal marine environments in South Eastern Australia, its potential sources and pathways [written]

This study estimated the concentration of floating microplastics (i.e. plastics measuring less than 5mm; reported in unit of pieces/m3) in the Great Barrier Reef Marine Park, Australia collected from 2020-03-16 to 2020-03-24. Microplastics in the surface water were collected using a manta net. This dataset contains the results from all 16 surface water samples, in a spreadsheet format.

A review of peer-reviewed publications was undertaken, focusing on coastal and marine microplastics relevant to South Eastern Australia (South Australia, Victoria, and New South Wales), as well as from ongoing citizen science programmes from AUSMAP (https://www.ausmap.org/). This dataset summarises basic information about the microplastics studies: the location of the study; if the study focused on water, sediment or biota; the type of biota (for biotic studies); and the DOI of the publication. Although the primary focus of this study was restricted to southeastern Australia, studies collated from other regions have also been included in this dataset. The outcomes of the literature review for other regions (QLD, NT, SA, WA, Tas) should not be considered comprehensive.

A review of peer-reviewed publications was undertaken, focusing on coastal and marine microplastics relevant to South Eastern Australia (South Australia, Victoria, and New South Wales), as well as from ongoing citizen science programmes from AUSMAP (https://www.ausmap.org/). This dataset summarises basic information about the microplastics studies: the location of the study; if the study focused on water, sediment or biota; the type of biota (for biotic studies); and the DOI of the publication. Although the primary focus of this study was restricted to southeastern Australia, studies collated from other regions have also been included in this dataset. The outcomes of the literature review for other regions (QLD, NT, SA, WA, Tas) should not be considered comprehensive.

This study estimated the concentration of microplastics (i.e. plastics measuring less than 5mm) in seawater (reported in unit of items/m3), and sediments (reported in unit of items/kg d.w.), in the Hangzhou Bay, China during 2020-09-11 to 2020-11-21. Microplastics in the seawater were collected using a plankton net while those in the sediment were collected using a sediment grab sampler. Data on hydrologic conditions in the study area were also collected. These include water depth (reported in unit of m), seawater temperature (reported in unit of oC), seawater dissolved oxygen (reported in unit of mg/L), seawater pH, and seawater salinity (reported in unit of ‰). This dataset contains the results from all 26 seawater, and 26 sediment samples, in a spreadsheet format.

This study estimated the concentration of microplastics (i.e. plastics measuring less than 5mm, reported in unit of pieces/kg d.w.) on beaches along the western Gulf of Thailand during 2019-09-22. Microplastic data were collected using a metal spoon. This dataset contains the results from all 25 beach samples, in a spreadsheet format.

This study estimated the amount of microplastics (i.e. plastics measuring less than 5 mm; reported in unit of pieces/m2), mesoplastics (i.e. plastics measuring 5-20 mm; reported in unit of counts/m2), macroplastics (i.e. plastics measuring 20-100 mm; reported in unit of counts/m2), and megaplastics (i.e. plastics measuring over 100 mm; reported in unit of counts/m2) in Maracas Beach, a micro-tidal recreational beach located on the north coast of Trinidad. These plastics were collected from 2015-09-27 to 2016-02-22 during multiple beach profile surveys. This dataset contains the results from all 18 beach surveys, in a spreadsheet format.