Managing microplastics in south-eastern Australian coastal waters: identifying knowledge gaps

Microplastics in coastal and marine environments are a priority issue for multiple stakeholders, including local and state governments, water utilities and the general public. To define guidelines and support policy actions that curb microplastic pollution, managers and decision-makers require clear, synthesised information on the occurrence of microplastics in coastal and marine environments, including potential sources and pathways and exposure risk. Engagement is key to understanding shared needs, barriers and opportunities for the management of microplastics, as well as to develop solutions at a multi-state (national) level.

This project consolidated our understanding of microplastics in coastal marine environments of south-eastern Australia (South Australia, Victoria and New South Wales). The project team engaged with research, regulatory and government agencies, and non-government organisations, to identify their information needs, synthesised existing data, and identified research priorities for managing plastic pollution.

Approach and findings

A literature review highlighted the main methodological approaches, findings and limitations, including information on potential sources and pathways where available. Multiple stakeholders were engaged through an online workshop and an anonymous survey to identified critical gaps in knowledge and future research priorities. These research priorities respond to cross-sector stakeholder needs, and support evidence-based policy, regulation and management.

Overall, few studies had covered microplastics in water, sediments, and biota. Most importantly, there was a lack of repeated sampling, and inconsistency in methodological approaches. This meant the results were rarely comparable. The main focus of studies was to was to document the occurrence and load of microplastic in coastal environments. While polymer validation was undertaken, few studies effectively establish a causal link to potential sources and pathways. There was also limited or no assessment of ecological impacts. Nonetheless, microplastics were ubiquitous in estuarine, coastal and deeper offshore areas. Fibres and fragments were dominant, and microplastic abundance was associated with environmental and urban features such as urban landscapes/population density and stormwater.

The importance of wastewater treatments, stormwater and road dust on microplastic occurrence is also highlighted, though there is still a lack of targeted research evidence across the three states, in particular on road dust and microplastics from tyre wear. Beach surveys were a large source of information but generally focus on visible debris, and often report only larger microplastics (1–5 mm, with microbeads or fibres too small to be sampled effectively). Despite collection or activity-related limitations, beach surveys have shown broad-scale and long-term trends in abundance of smaller microplastics.

Engagement with researchers, government, water utilities and non-government organisations was pivotal to providing a deeper analysis of ongoing research and available information. It also provided a forum for broad discussions and to evaluate perspectives on cross-sector needs. Expert opinion covered a diverse range of topics, from methodological and analytical method development, monitoring, and reconstructing sources and pathways, including modelling, risk assessment or ecotoxicology. Ultimately, it allowed the project team to identify major priorities to support monitoring and management that can be sought through collaboration and shared understanding, striving towards a national-level application.

The project report summarises major knowledge gaps, and cross-sector priority actions, solutions and recommendations that can contribute to supporting meaningful management and policy strategies for microplastics in coastal environments. These are framed under three overarching research priorities:

• Need for method harmonisation to increase reproducibility and data comparability (there was strong support for refining methodological approaches and establishing standardised guidelines to determine microplastic contamination and combat the lack of comparable data).
• Need to understand occurrence of microplastics and identify sources and reconstruct possible pathways into the environment (promote repeated sampling, document spatiotemporal variation, unravel the environmental and anthropogenic factors driving variations over time and space; allied to source identification and pathway reconstruction, as well as increase the quantification and characterisation of smaller microplastics (<1 mm) for which information is comparatively scarce but likely more relevant regarding ecological impacts).
• Need to demonstrate the risk of harm to individuals and ecosystems (understand the biological and ecological impacts of different microplastics and demonstrate their risk of harm, including as vectors of chemical contamination, to support risk assessments; as well as translating toxicological impacts at sub- or individual levels to higher level population and ecological consequences).

Outcomes

Researchers, governments, water utilities and non-government organisations have a new, shared understanding of microplastics in coastal marine environments of south-eastern Australia (South Australia, Victoria and New South Wales). The identification and synthesis of existing knowledge and the needs of research users sets a direction for future research required to manage microplastic pollution.

Project location

National