Microplastics and Zooplankton
An Environmental Indicator
START
INTRODUCTION
Protecting the marine environment has become one of the major concerns of our time, and a priority in Europe. Marine and coastal areas are home to a high level of human activity, which is exerting increasing pressure on the marine environment. The United Nations Environment Programme (UNEP) recognizes that we are facing a triple global crisis, characterized by anthropogenic climate change, biodiversity loss, and pollution. Human discharges of synthetic chemicals, including plastics, onto land and into the oceans have reached a critical threshold, with negative impacts on human health and the stability of the Earth system (Persson et al., 2022).
Plastics are a ubiquitous source of pollution throughout their life cycle, including production, use, and waste management. The use of fossil fuels for their manufacture also contributes to climate change, as increased plastic production leads to a growing accumulation of marine debris, disrupting diversity and biogeochemical cycles and promoting the spread of invasive species, pathogens, and antibiotic-resistance genes (Landrigan et al., 2023).
Global Impact of Plastic Pollution: Effects on Ecosystems, Climate, and Biodiversity
+ info
Plastics decrease in size as weathering and fragmentation occur, increasing the risk of ingestion by a wide range of organisms. Microplastics are similar in size to zooplankton, making them more likely to be mistaken for food by marine organisms.
Ecosystem Impact
+ info
Study Objective
The Marine Strategy Framework Directive (MSFD) is a European Union legislative framework aimed at protecting the marine environment across Europe. The MSFD aims to implement action and monitoring programs whose objective is to achieve a 'good ecological status' (GES) of European marine waters. In this research, we investigate the potential risk of ingesting plastic particles mistaken for zooplankton. This study aims to determine whether the quantities of plastic relative to zooplankton in the aquatic environment can serve as an environmental risk indicator and reflect the state of pollution in the sea. Plastic and zooplankton samples were taken from the North Sea, Elbe River, and Thames River to assess the proportion of zooplankton organisms in contact with microplastics in the surface layer (plastic: zooplankton ratio).
This study aims to determine whether the quantities of plastic relative to zooplankton in the aquatic environment can serve as an environmental risk indicator and reflect the state of pollution in the sea.
Methodology and Sampling Areas
Plastic and zooplankton for this study were collected along 18 stations in surface water samples from the Thames River, the Elbe River, and the North Sea during different seasonal campaigns in 2022 and 2023. Sampling sites included freshwater, tidal, and estuarine regions in the Elbe and Thames, as well as offshore locations in the North Sea. In the Thames and Elbe rivers, as well as in the North Sea, larger floating microplastics were collected with a Manta net (>335 µm), with the net mounted on a catamaran frame for stability in the North Sea. Samples were fixed immediately with 4% buffered formalin.
Plastic and Zooplankton Analysis
Plastics were manually sorted from samples using a dissecting stereomicroscope. Each sample was examined twice to ensure the detection of most plastic particles. Plastics were counted and weighed, and, grouped by size class: micro (<5 mm), meso (5-20 mm), and macro (> 20 mm).Plastics were digitally imaged using a ZooScan scanner system with a resolution of 2400 dpi. Plastic and zooplankton were automatically detected, and their morphological attributes were extracted through post-processing with Zooprocess and Plankton Identifier software. Data were then exported to Ecotaxa.
Zooplankton Concentration
+ info
Plastic Concentration
+ info
Pipeline for plastic analysis
Results
Plastic concentration was highest in the Thames River, with an average of 10.10 plastics m-³, followed by the Elbe (0.8 plastics m-³) and the North Sea (0.38 plastics m-³).
In contrast, the North Sea showed similar plastic concentrations in winter (0.43 plastics m-³) and summer (0.34 plastics m-³).
In the Elbe, average plastic concentrations were 0.21 plastics m-³ in winter and 0.17 plastics m-³ in the summer of 2022
Thames River
Elbe River
North Sea
Plastic-to-Zooplankton Ratio (PZR)
Using total plastic and zooplankton abundance, we calculated the plastic-to-zooplankton ratio (PZR), defined as the number of plastic debris pieces per m³ divided by the number of zooplankton organisms per m³. The spatial distribution of PZR varies by 5 orders of magnitude across the studied area, with the lowest value (0.00002) in the North Sea during summer and the highest ratio found in the estuarine part of the Thames River in winter 2023 (23.3).Overall, the PZR was higher in the two rivers than in the North Sea stations. This suggests that filter feeders, which consume zooplankton, have a 2.9 in 10 chance of ingesting plastic instead of plankton.
Conclusions and Next Steps
This study proposes a new tool for assessing the potential risk of plastic ingestion by marine fauna. Zooplankton ratio or PZR provides insights into the environmental risk posed by plastic pollution on marine food webs. Future research will expand analysis to the water column and integrate hydrological and current patterns to better assess pollution risks. Establishing thresholds for this indicator is crucial for future monitoring efforts.
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FOLLOW US!
Zooplankton were present across all sampling stations, with concentrations varying by location and season. The highest concentration was found in the North Sea during summer (St9; 10,772.3 ind. m⁻³), while the lowest was in the estuarine part of the Thames River in winter 2023 (station T6; 0.07 ind. m⁻³).Zooplankton plays a crucial role in marine food webs, serving as prey for fish, whales, and crustaceans. Any disruption in their abundance due to plastic pollution could have cascading effects on marine ecosystems.
Filter-feeding species, such as certain fish and whales, could potentially ingest MPs. The potential ingestion of microplastics poses a risk of entering and transferring upwards the trophic chain, ultimately affecting humans.
Plastic pollution is now omnipresent throughout the world, from our cities to the oceans, in the Arctic and Antarctic, via marine and atmospheric routes, and across layers of biological function (Morrison et al., 2022). The vast majority of aquatic plastic exists in the form of microplastics (MPs) often less than 5 mm in size. More recent studies estimate that there are 24.4 trillion pieces of MPs in the world's upper oceans, which could total between 82,000 and 578,300 tons of these pollutants (Isobe et al., 2021).
A) Plastic debris were manually sorted from samples B-C) Plastics were scanned by ZooScan and image processed with Zooprocess to assess a large set of morphological parameters. D) Example of sorted plastic categories fragments and E) Copepods.
Plastic analyses revealed the presence of plastics at all sampling stations. Plastic concentration was highest in the Thames River, with an average of 10.10 plastics m-³, followed by the Elbe (0.8 plastics m-³) and the North Sea (0.38 plastics m-³). In the Thames, average plastic concentrations were 2.53 plastics m-³ in winter and 2.44 plastics m-³ in summer 2022. However, in 2023, very high concentrations were observed at the two monitored stations closest to London: T5 (34.32 plastics m-³) in winter and T6 (118.4 plastics m-³) in spring.
Microplastics and Zooplankton
Estibaliz Garmendia
Created on February 12, 2025
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Transcript
Microplastics and Zooplankton
An Environmental Indicator
START
INTRODUCTION
Protecting the marine environment has become one of the major concerns of our time, and a priority in Europe. Marine and coastal areas are home to a high level of human activity, which is exerting increasing pressure on the marine environment. The United Nations Environment Programme (UNEP) recognizes that we are facing a triple global crisis, characterized by anthropogenic climate change, biodiversity loss, and pollution. Human discharges of synthetic chemicals, including plastics, onto land and into the oceans have reached a critical threshold, with negative impacts on human health and the stability of the Earth system (Persson et al., 2022).
Plastics are a ubiquitous source of pollution throughout their life cycle, including production, use, and waste management. The use of fossil fuels for their manufacture also contributes to climate change, as increased plastic production leads to a growing accumulation of marine debris, disrupting diversity and biogeochemical cycles and promoting the spread of invasive species, pathogens, and antibiotic-resistance genes (Landrigan et al., 2023).
Global Impact of Plastic Pollution: Effects on Ecosystems, Climate, and Biodiversity
+ info
Plastics decrease in size as weathering and fragmentation occur, increasing the risk of ingestion by a wide range of organisms. Microplastics are similar in size to zooplankton, making them more likely to be mistaken for food by marine organisms.
Ecosystem Impact
+ info
Study Objective
The Marine Strategy Framework Directive (MSFD) is a European Union legislative framework aimed at protecting the marine environment across Europe. The MSFD aims to implement action and monitoring programs whose objective is to achieve a 'good ecological status' (GES) of European marine waters. In this research, we investigate the potential risk of ingesting plastic particles mistaken for zooplankton. This study aims to determine whether the quantities of plastic relative to zooplankton in the aquatic environment can serve as an environmental risk indicator and reflect the state of pollution in the sea. Plastic and zooplankton samples were taken from the North Sea, Elbe River, and Thames River to assess the proportion of zooplankton organisms in contact with microplastics in the surface layer (plastic: zooplankton ratio).
This study aims to determine whether the quantities of plastic relative to zooplankton in the aquatic environment can serve as an environmental risk indicator and reflect the state of pollution in the sea.
Methodology and Sampling Areas
Plastic and zooplankton for this study were collected along 18 stations in surface water samples from the Thames River, the Elbe River, and the North Sea during different seasonal campaigns in 2022 and 2023. Sampling sites included freshwater, tidal, and estuarine regions in the Elbe and Thames, as well as offshore locations in the North Sea. In the Thames and Elbe rivers, as well as in the North Sea, larger floating microplastics were collected with a Manta net (>335 µm), with the net mounted on a catamaran frame for stability in the North Sea. Samples were fixed immediately with 4% buffered formalin.
Plastic and Zooplankton Analysis
Plastics were manually sorted from samples using a dissecting stereomicroscope. Each sample was examined twice to ensure the detection of most plastic particles. Plastics were counted and weighed, and, grouped by size class: micro (<5 mm), meso (5-20 mm), and macro (> 20 mm).Plastics were digitally imaged using a ZooScan scanner system with a resolution of 2400 dpi. Plastic and zooplankton were automatically detected, and their morphological attributes were extracted through post-processing with Zooprocess and Plankton Identifier software. Data were then exported to Ecotaxa.
Zooplankton Concentration
+ info
Plastic Concentration
+ info
Pipeline for plastic analysis
Results
Plastic concentration was highest in the Thames River, with an average of 10.10 plastics m-³, followed by the Elbe (0.8 plastics m-³) and the North Sea (0.38 plastics m-³).
In contrast, the North Sea showed similar plastic concentrations in winter (0.43 plastics m-³) and summer (0.34 plastics m-³).
In the Elbe, average plastic concentrations were 0.21 plastics m-³ in winter and 0.17 plastics m-³ in the summer of 2022
Thames River
Elbe River
North Sea
Plastic-to-Zooplankton Ratio (PZR)
Using total plastic and zooplankton abundance, we calculated the plastic-to-zooplankton ratio (PZR), defined as the number of plastic debris pieces per m³ divided by the number of zooplankton organisms per m³. The spatial distribution of PZR varies by 5 orders of magnitude across the studied area, with the lowest value (0.00002) in the North Sea during summer and the highest ratio found in the estuarine part of the Thames River in winter 2023 (23.3).Overall, the PZR was higher in the two rivers than in the North Sea stations. This suggests that filter feeders, which consume zooplankton, have a 2.9 in 10 chance of ingesting plastic instead of plankton.
Conclusions and Next Steps
This study proposes a new tool for assessing the potential risk of plastic ingestion by marine fauna. Zooplankton ratio or PZR provides insights into the environmental risk posed by plastic pollution on marine food webs. Future research will expand analysis to the water column and integrate hydrological and current patterns to better assess pollution risks. Establishing thresholds for this indicator is crucial for future monitoring efforts.
+ info
FOLLOW US!
Zooplankton were present across all sampling stations, with concentrations varying by location and season. The highest concentration was found in the North Sea during summer (St9; 10,772.3 ind. m⁻³), while the lowest was in the estuarine part of the Thames River in winter 2023 (station T6; 0.07 ind. m⁻³).Zooplankton plays a crucial role in marine food webs, serving as prey for fish, whales, and crustaceans. Any disruption in their abundance due to plastic pollution could have cascading effects on marine ecosystems.
Filter-feeding species, such as certain fish and whales, could potentially ingest MPs. The potential ingestion of microplastics poses a risk of entering and transferring upwards the trophic chain, ultimately affecting humans.
Plastic pollution is now omnipresent throughout the world, from our cities to the oceans, in the Arctic and Antarctic, via marine and atmospheric routes, and across layers of biological function (Morrison et al., 2022). The vast majority of aquatic plastic exists in the form of microplastics (MPs) often less than 5 mm in size. More recent studies estimate that there are 24.4 trillion pieces of MPs in the world's upper oceans, which could total between 82,000 and 578,300 tons of these pollutants (Isobe et al., 2021).
A) Plastic debris were manually sorted from samples B-C) Plastics were scanned by ZooScan and image processed with Zooprocess to assess a large set of morphological parameters. D) Example of sorted plastic categories fragments and E) Copepods.
Plastic analyses revealed the presence of plastics at all sampling stations. Plastic concentration was highest in the Thames River, with an average of 10.10 plastics m-³, followed by the Elbe (0.8 plastics m-³) and the North Sea (0.38 plastics m-³). In the Thames, average plastic concentrations were 2.53 plastics m-³ in winter and 2.44 plastics m-³ in summer 2022. However, in 2023, very high concentrations were observed at the two monitored stations closest to London: T5 (34.32 plastics m-³) in winter and T6 (118.4 plastics m-³) in spring.