These methods will differ among environments so refer to the relevant section:
Water
All data should aim to be publicly released, unless circumstances restrict this (e.g., confidentiality or embargo, grant agreement, etc.). In situations where data cannot be shared, the metadata should still be made available. (Ideally, four key metrics should be reported for microplastic from environmental water samples.
- **Load
**This provides information on how much microplastic was detected per collection, and enables comparisons of microplastic load with other work to better understand how much plastic is in coastal and marine environments, and whether levels can change in space and time. Reporting units (e.g., MPs/m3, MPs/area or MPs/transect) should be considered during the sampling design phase and checked for applicability to the research question. Although reporting units are often related to specific research goals, providing supplementary information with the raw data or transformed data in complementary units is recommended to allow broadscale comparisons among studies. -
Physical characteristics
This provides information about the types of microplastics present in the environment and is essential given the diversity of microplastic, shapes, sizes and colours. This information can provide both knowledge on risks associated with the presence of different microplastic types and assist managers in making informed decisions to reduce the input of key plastic items into waterways.
-
Chemical characteristics
This provides information on polymer type, the presence of additives, and other chemicals, as well as potential evidence of weathering (e.g., age, biofilm, degradation).
-
**Contextual information **
Information, particularly describing local and regional environmental and biotic variables can help researchers make like-for-like comparisons. For example, for seawater samples, factors such as wind and swell direction, depth and presence of oceanographic features (e.g., slicks) at the collection site, as well as the location of potential point-sources of contamination (e.g., WWTP outflows, sewer or drainwater outflows) can influence plastic input rates, and can inform possible sources and fates.
Reporting microplastic load
It is essential that microplastic data is reported in number per area or volume, with defining morphological characteristics such as shape, colour, size, texture, and polymer type also included. Where possible, data for larger microplastics should also be reported in mass; noting small microplastics (<1 mm) can be difficult to weigh. However, it is recommended they are weighed where there is high loading in the sample and they can be combined as an indicator of plastic mass, while reporting counts of polymer types. Additionally, reporting the measure of variability and replication is also essential.
Essential parameters:
- Average number (±SD or SE) of MP per area (# particles km<sup>-2</sup>, # particles m<sup>-2</sup>)
- Average number (±SD or SE) of MP per volume (# particles L<sup>-1</sup>)
- Average mass (±SD or SE) of MP per area (g MP km<sup>-2</sup>, g MP m<sup>-2</sup>)
- Average mass (±SD or SE) of MP per volume (g MP L<sup>-1</sup>, g MP m<sup>-3</sup>)
Desirable parameters:
- Average number (±SD or SE) polymers per volume (e.g., # of nylon fibres m<sup>-3</sup>)
- Average number (±SD or SE) of MP size category per volume (e.g., # of MPs 20-300 μm m<sup>-3</sup>)
- Average number (±SD or SE) of MP colour category per volume (e.g., # of blue MPs m<sup>-3</sup>)
Reporting physical and chemical characteristics
Harmonisation in the reporting of physical data is challenging primarily due to the heterogeneity of microplastics, however, there is essential basic morphological data that is required for early identification and verification of polymer assignment (i.e., through the elimination of potential contaminants) and desirable information that is project specific.
Essential parameters:
- Maximum length
- Maximum width perpendicular to the length
- Surface area (of the item sitting flat)
- Mass (for visible microplastics > 1mm)
- Colour (RGB and HSV for larger microplastics)
- Shape (e.g., fragment, pellet, foam, fibre, film, line, tyre dust)
- Polymer (for microscopic 1 μm - 1 mm microplastics)
- Detection limits for the count and minimum microplastic size
Desirable parameters:
- Mass per item and/or type
- Polymer (for visible microplastics >1 mm)
- Percentage of microplastics and natural particles present
Reporting contextual information
It is important to consider and report information on the environmental variables at the time of collection. Where possible this information should be collected at the time of sampling, but some data and information can be calculated in hindsight (distance travelled using GPS location data) or attained through in situ sensors, but all should be recorded where feasible.
General site information
- Location (including latitude and longitude coordinates)
- Location description [physical features, biotic features of the area (e.g., algal coverage) and habitat type]
- Date of data collection; season
- Recent weather events (e.g., dust storms, cyclones, floods) and conditions during sampling event (e.g., temperature, wind, rain)
- Wind speed and direction
- Swell height and direction
- Collection depth, temperature and salinity
- Tide
- Vessel speed
- Tow direction and/or depth profile
- Proximity to urban and/or industrial areas
- Proximity to river streams and/or estuaries
- Proximity to wastewater treatment plants and number of outflows, drain or stormwater outlets and other potential point sources of contamination
- Presence of floating macro and meso plastics in the immediate area of collection or in the sample
- Presence of organisms in the immediate area of collection or in the sample
- Presence of oceanographic features as indicators of marine processes (e.g., sea slicks) in the immediate area of collection
Sediment
All data should aim to be publicly released, unless circumstances restrict this (e.g., confidentiality or embargo, grant agreement, etc.). In situations where data cannot be shared, the metadata should still be made available. Ideally, four key metrics should be reported for microplastic from sediment samples.
- **Load
**This provides information such as how much microplastic was detected in the sediment and enables comparisons of microplastic load with other work to better understand how much plastic is in coastal and marine environments. Reporting units (e.g., number or mass of microplastics per cubic metre, sampled area or transect) should be considered during the design phase and checked for applicability to the research question. Although reporting units are often related to specific research goals, providing supplementary information with the raw data or transformed data in complementary units is recommended to allow broadscale comparisons among studies. -
Physical characteristics
This provides information about types of microplastics present in the environment, and is essential given the diversity of microplastic, shapes, sizes, and colours. This information can provide both knowledge on risks associated with the presence of different microplastic types and assist managers in making informed decisions to reduce the input of key items.
-
Chemical characteristics
This provides information on polymer type, presence of additives and other chemicals, as well as potential evidence of weathering (e.g., age, biofilm, degradation).
-
**Contextual information **
Information, particularly describing environmental and biotic variables can help researchers make like-for-like comparisons. For example, for coastal sediment samples, factors such as wind and swell direction, local hydrodynamics, sedimentology, and location of potential point-sources of contamination (e.g., WWTP outflows, sewer or drainwater outflows) can influence plastic input rates and can inform possible sources and fates.
Reporting microplastic load
It is essential that microplastic load is reported in units commensurate with the method, e.g., number per mass in grab samples, number per area in quadrat and transect samples. Reporting mass of microplastic is desirable. Where possible, is it recommended that data for larger microplastics should also be reported in mass; noting small microplastics (<1 mm) can be difficult to weigh, particularly if they are damaged during spectroscopy (GESAMP, 2019). However, it is recommended they are weighed where there is high loading in the sample and they can be combined as an indicator of plastic mass, while reporting counts of polymer types.Additionally, reporting the measure of variability and replication is also essential.
Essential parameters:
- Average number (±SD or SE) of MP per area (# particles km<sup>-2</sup>, # particles m<sup>-2</sup>)
- Average number (±SD or SE) of MP per volume (# particles m<sup>-3</sup>)
- Average number (±SD or SE) of MP per mass (# particles kg<sup>-1</sup> dry sediment)
- Average mass (±SD or SE) of MP per area (g MP km<sup>-2</sup>, g MP m<sup>-2</sup>)
- Average mass (±SD or SE) of MP per volume (g MP L<sup>-1</sup>, g MP m<sup>-3</sup>)
- Average mass (±SD or SE) of MP per mass (g MP g<sup>-1</sup>)
Desirable parameters:
- Average number (±SD or SE) polymers per volume (e.g., # of nylon fibres m<sup>-3</sup>)
- Average number (±SD or SE) of MP size category per volume (e.g., # of MPs 20-300 μm m<sup>-3</sup>)
- Average number (±SD or SE) of MP colour category per volume (e.g., # of blue MPs m<sup>-3</sup>)
Reporting physical and chemical characteristics
Harmonisation in the reporting of physical data is challenging primarily due to the high heterogeneity between microplastics, however, there is essential morphological data that is needed for early identification and verification of polymer assignment (i.e., through elimination of potential contaminants) and desirable information that is project specific.
Essential parameters:
- Maximum length
- Maximum width perpendicular to the length
- Surface area (of the item sitting flat)
- Mass (for visible microplastics > 1mm)
- Colour (RGB and HSV for larger microplastics)
- Shape (e.g., fragment, pellet, foam, fibre, film, line, tyre dust)
- Polymer (for microscopic 1 μm - 1 mm microplastics)
- Detection limits for the count and minimum microplastic size
Desirable parameters:
- Mass per item and/or type
- Polymer (for visible microplastics >1 mm)
- Percentage of microplastics and natural particles
Reporting contextual information
Supratidal, intertidal, and subtidal zones can have a variety of ecosystems and habitats. It is important to consider and report information that fully describes the sampling habitat, including environmental variables, to maximise comparisons among sites and studies, namely on the following variables:
General site information
- Location (including latitude and longitude coordinates)
- Location description [physical features, biotic features of the area (e.g., algal coverage, crab holes, oyster beds) and habitat type]
- Date of data collection; season
- Recent weather events (e.g., dust/sandstorms, cyclones, floods) and conditions during sampling event (e.g., temperature, wind, rain, tide)
- Proximity to urban and/or industrial areas
- Proximity to river streams and/or estuaries
- Proximity to wastewater treatment plants and number of outflows, drain or stormwater outlets and other potential point sources of contamination
- Number of waste bins
- Proximity to beach infrastructures (e.g., surf clubs, cafes, restaurants, shopping precincts, nightclubs)
Intertidal sediment
- Type of sediment, determined by granulometry
- Beach slope (including sand migration)
- Wind speed and direction
- Amount of macro and meso marine litter in the vicinity area of collection
- Presence of organisms in the area of collection or in the sample
- Tide (last high tide)
Subtidal sediment
- Type of sediment, determined by Granulometry and %TOC
- Wave height
- Collection depth, temperature, and salinity
- Amount of floating macro and meso plastics in the vicinity of area of collection
- Presence of organisms in the area of collection or in the sample
- Hydrodynamic profile
Note, not all of this information needs to be collected at the time of sampling but can be recorded in hindsight (using GPS location data), or attained through in situ sensors, but all should be recorded.
Biota
All data should aim to be publicly released, unless circumstances restrict this (e.g., confidentiality or embargo, grant agreement, etc.). In situations where data cannot be shared, the metadata should still be made available. Ideally, four key metrics should be reported for microplastic in biota samples.
- **Load
**This provides information such as how much microplastic was detected in biota, and enables comparisons of microplastic load with other work to better understand how much plastic is in biota across different environments, and whether levels are changing. Reporting units (e.g., average number of microplastics per organism, or tissue weight) should be considered during the sampling design phase and checked for applicability to the research question. Although reporting units are often related to specific research goals, providing supplementary information with raw data or transformed data in complementary units is recommended to allow broadscale comparisons among studies. -
Physical characteristics
This provides information on the types of microplastics present in the environment, and is essential given the diversity of microplastic shapes, sizes and colours. This information can both provide knowledge on risks associated with the uptake and presence of different microplastic types and assist managers in making informed decisions to reduce the input of key items.
-
Chemical characteristics
This provides information on polymer type, presence of additives and other chemicals, as well as potential evidence of weathering (e.g., age, biofilm, degradation).
-
**Contextual information **
Information, particularly around environmental and biotic variables, can help researchers make like-for-like comparisons. For example, for biotic samples, colony size, scat photos, other fishery collected alongside the target species, and samples of plastic items from the vessel, fishing gear, storage containers can all be used to interrogate and contextualise the microplastics data.
Reporting microplastic load
Microplastics must be reported in number of microplastics per organism and/or per weight of tissue, with defining morphological characteristics such as shape, colour, size, texture, and polymer type also included. Where possible, data for larger microplastics should also be reported in mass; noting small microplastics (< 1 mm) can be difficult to weigh. However, it is recommended they are weighed where there is high loading in the sample and they can be combined as an indicator of overall plastic mass, while also reporting counts of polymer types. Additionally, reporting the measure of variability in microplastic load and sample replication is also essential.
Essential parameters:
- Average number (±SD or SE) of microplastics extracted from all organisms (# particles per organism)
- Average number (±SD or SE) of microplastics extracted from organisms found to contain plastic (# particles per contaminated organisms)
- Total number of individuals analysed
- Number of individuals containing at least one microplastic piece (reported as a percentage of frequency of occurrence)
Desirable parameters:
- Mass per microplastic item and/or type
- Polymer (for all microplastics)
It is also important to report, when possible, the different physical characteristics of the microplastic pieces when reporting results (e.g., 10 nylon fibres L-1; 4 grams of nurdles m-3). This extra information is important in allowing appropriate comparisons between data sets, as well as providing useful data for higher-level users (e.g., policy makers).
Reporting microplastic physical characteristics
Harmonising the reporting of physical data is challenging due to the heterogeneity of microplastics (Refer to Introduction and scope); however, there is essential morphological data that is needed to contextualise microplastics that have been taken up by biota. For example, Antarctic krill can significantly alter the physical size of ingested spherical microplastics (from 31.5 µm to 1 µm in diameter; (Dawson et al., 2018)). If smaller items are found, then one would expect larger items of the same polymer type to be in the surrounding water. While there is little evidence that the digestion system or associated microbiome can decompose microplastics (plastics are inert due to their low chemical reactivity), recording details of the specific compartment (i.e., stomach that contains digestive enzymes vs cloaca that is high in organic waste) in which the microplastic was retrieved is important.
Essential parameters:
- Maximum length
- Maximum width perpendicular to the length
- Surface area (of the item sitting flat)
- Mass (for visible microplastics > 1mm)
- Colour (RGB and HSV for larger microplastics)
- Shape (e.g., fragment, pellet, foam, fibre, film, line, tyre dust)
- Polymer (for microscopic 1 μm - 1 mm microplastics)
- Biotic compartment
- Detection limits for the count and minimum microplastic size
Desirable parameters:
- Mass per item and/or type
- Polymer (for all microplastics)
- Percentage of microplastics and natural particles present.
Meta data and contextual information
It is important to consider and report information on the following environmental variables at time of collection. Where possible, this information should be collected at the time of sampling, but some data can be calculated in hindsight (e.g., GPS location data). Information pertaining to the biology and anatomy of the target species should also be gathered to understand the impacts of the microplastics exposure.
General site information
- Location (including latitude and longitude coordinates)
- Location description (physical features, features of the area, e.g., algal coverage)
- Habitat type including presence of prey items and predators
- Date of data collection; season
- Recent weather and weather conditions during sampling event (e.g., temperature, wind, rain, recent weather events such as dust storms, cyclones, floods)
- Wind speed and direction
- Wave height
- Tide
- Collection depth, temperature and salinity
- Proximity to urban and/or industrial areas
- Proximity to river streams and/or estuaries
- Proximity to wastewater treatment plants and number of outflows, drain or stormwater outlets and other potential point sources of contamination
- Presence of macro, meso and microplastics in the immediate environment (i.e., water column, sediment)
- Target species behaviour
Air
All data should aim to be publicly released, unless circumstances restrict this (e.g., confidentiality or embargo, grant agreement, etc.). In situations where data cannot be shared, the metadata should still be made available. Ideally, four key metrics should be reported for microplastic from air samples.
- **Load
**This provides information such as how much microplastic was detected per collection and enables comparisons of microplastic load with other work to better understand how much plastic is in the environment. Reporting units (e.g., MPs m-3, particle m-2 d-1) should be considered during the sampling design phase and checked for applicability to the research question. Although reporting units are often related to specific research goals, providing supplementary information with the raw data or transformed data in complementary units is recommended to allow broadscale comparisons among studies. -
Physical characteristics
This provides information on the types of microplastics present in the environment, and is essential given the diversity of microplastic shapes, sizes and colours. This information can provide both knowledge on the risks associated with the presence of different microplastic types and assist managers in making informed decisions to reduce the input of key plastic items into the environment.
-
Chemical characteristics
This provides information on the polymer types, presence of additives or other chemicals, as well as potential evidence of weathering (e.g., age, biofilm, degradation).
-
**Contextual information **
Information, particularly describing local and regional environmental and biotic variables can help researchers make like-for-like comparisons. For example, for air samples, wind strength and direction, or location of potential point-sources of contamination (e.g., industry) can influence plastic input rates.
Reporting microplastic load
It is essential that microplastic load in air is reported as number per volume or area, with defining morphological characteristics also included, such as shape, colour, size, texture, polymer type. Where possible, data for larger microplastics should also be reported in mass; noting small microplastics (<1 mm) can be difficult to weigh. However, it is recommended they are weighed where there is high loading in the sample and they can be combined as an indicator of plastic mass, while reporting counts of polymer types. Additionally, reporting the measure of variability and replication is also essential.
Essential parameters:
- Average number (±SD or SE) of MPs per volume (# particles m<sup>-3</sup> for active sampling)
- Average number (±SD or SE) of MPs per area (# of particle.m<sup>-2</sup> d<sup>-1</sup> for passive sampling)
- Average mass (±SD or SE) of MP per volume (g MP m<sup>-3</sup>)
- Average mass (±SD or SE) of MP per area (g MP m<sup>-2</sup> d<sup>-1</sup>)
Desirable parameters:
- Average number (±SD or SE) polymers per volume (e.g., # of nylon fibres m<sup>-3</sup> for active sampling)
- Average number (±SD or SE) polymers per area (e.g., # of nylon fibres m<sup>-2</sup> d<sup>-1</sup> for passive sampling)
- Average number (±SD or SE) of MP size category per volume (e.g., # of MPs 20-300 m<sup>-2</sup> d<sup>-1</sup> for passive sampling)
- Average number (±SD or SE) of MP size category per area (e.g., # of MPs 20-300 μm m<sup>-3</sup>)
- Average number (±SD or SE) of MP colour category per volume (e.g., # of blue MPs m<sup>-3</sup>)
- Average number (±SD or SE) of MP colour category per area (e.g., # of blue MPs m<sup>-2</sup> d<sup>-1</sup> for passive sampling)
For conversion between units, we recommend using the formula in Leusch and Ziajahromi (2021).
Reporting physical and chemical characteristics
The harmonisation of physical data is challenging primarily due to the high heterogeneity between microplastics; however, there is essential morphological data that is required for early identification and verification of polymer assignment (i.e., through elimination of potential contaminants) and desirable information that is project-specific.
Essential parameters:
- Maximum length
- Maximum width perpendicular to the length
- Surface area (of the item sitting flat)
- Mass (for visible microplastics > 1mm)
- Colour (RGB and HSV for larger microplastics)
- Shape (e.g., fragment, pellet, foam, fibre, film, line, tyre dust)
- Polymer (for microscopic 1 μm - 1 mm microplastics)
- Detection limits for the count and minimum microplastic size
Desirable parameters:
- Mass per item and/or type
- Polymer (for visible microplastics >1 mm)
- Percentage of microplastics and natural particles
Reporting contextual information
It is important to consider and report information on the environmental variables at the time of collection. Where possible, this information should be collected at the time of sampling, but some data can be calculated in hindsight (e.g., volume filtered).
**General site information **
- Location (including latitude and longitude coordinates)
- Location description (including physical features of the area)
- Date of data collection; season
- Weather conditions during sampling event (e.g., temperature, wind, rain)
- Recent weather events such as dust storms, cyclones, floods or others that may influence microplastic dispersal.
- Wind speed and direction
- Proximity to urban and/or industrial areas
- Proximity to river streams and/or estuaries
- Proximity to industrial infrastructure
- Proximity to roads
Note, not all of this information needs to be collected at the time of sampling, but can be recorded in hindsight (using GPS location data), but all should be recorded.