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Nutrient enrichment mediates the effect of biodegradable and conventional microplastics on macroinvertebrate communities
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A semi-natural mesocosm experiment compared the effects of biodegradable PLA microplastics and conventional HDPE microplastics on freshwater macroinvertebrate communities, finding that overall community effects were weak but that HDPE reduced invertebrate diversity more than PLA — except when nutrient enrichment was present, which erased this difference. The findings suggest that nutrient pollution interacts with microplastic type in complex ways, and that assessments of bioplastics as \"safer\" alternatives need to account for real-world co-stressors. More large-scale, long-term experiments are needed before drawing firm conclusions.
There is growing concern regarding the lack of evidence on the effects bioplastics may have on natural ecosystems, whilst their production continues to increase as they are considered as a greener alternative to conventional plastics. Most research is limited to investigations of the response of individual taxa under laboratory conditions, with few experiments undertaken at the community or ecosystem scale, either investigating microplastics independently or in combination with other pollutants, such as nutrient enrichment. The aim of this study is to experimentally compare the effects of oil-based (high density polyethylene - HDPE) with those of bio-based biodegradable (polylactic acid - PLA) microplastics and their interaction with nutrient enrichment on freshwater macroinvertebrate communities under seminatural conditions. There were no significant differences in total abundance, alpha and beta diversities, or community composition attributable to the type of microplastics, their concentration, or nutrient enrichment compared with the control. However, there was a significant difference in macroinvertebrate alpha diversity between high concentrations of both microplastic types under ambient nutrient conditions, with lower diversity in communities exposed to HDPE compared with PLA. Nutrient enrichment mediated the effect of microplastic type, such that the diversity of macroinvertebrate communities exposed to HDPE were similar to those communities exposed to PLA. These findings suggest that the effects of microplastic pollution on macroinvertebrate communities are very weak at large-scale settings under seminatural conditions and that these effects might be mediated by the nutrient status of freshwater ecosystems. More research under large-scale, long-term, seminatural settings are needed in order to elucidate the impact of both conventional plastics and bioplastics on natural environments and their interactive effect with other occurring stressors and pollutants.
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Contrasting the effects of microplastic types, concentrations and nutrient enrichment on freshwater communities and ecosystem functioning
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Researchers tested two types of microplastics, conventional polyethylene and biodegradable polylactic acid, in outdoor freshwater mesocosms and found that neither type significantly affected community composition or ecosystem functions like algae growth and leaf decomposition. Even at concentrations known to cause harm in lab settings, the microplastics had minimal impact when tested in more realistic ecological conditions. The study suggests that real-world microplastic effects on freshwater communities may differ from laboratory predictions.
Microplastic pollution and nutrient enrichment shift the diet of freshwater macroinvertebrates
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Researchers studied how microplastic pollution and excess nutrients together affect the feeding behavior of freshwater invertebrates in controlled experiments. They found that both conventional and biodegradable microplastics shifted what the organisms chose to eat, and these effects were amplified when combined with nutrient enrichment. The study suggests that microplastic pollution interacts with other common environmental stressors to alter freshwater food webs.
Combined impacts of micoplastic type, concentrations and nutrient loading on freshwater communities and ecosystems
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Researchers used 40 outdoor freshwater mesocosms to test the independent and interactive effects of microplastic type (conventional vs. bio-based biodegradable), particle concentration, and nutrient enrichment on pelagic community structure and ecosystem functions including phytoplankton biomass, periphyton productivity, and leaf litter decomposition, finding no significant impacts at the ecosystem scale.
Long-term effects of conventional and biodegradable microplastics from mulch on freshwater communities
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Researchers used outdoor mesocosms to study how conventional (polyethylene) and biodegradable (PBAT) microplastics from mulch films affect freshwater zooplankton and macroinvertebrate communities over 60 days, finding measurable community-level effects at environmentally relevant concentrations.
Biodegradability of microplastics reshapes surface biofilm microbial community structure and nitrogen cycling functions in aquatic environments
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Researchers compared how biodegradable (PLA) and non-biodegradable (polyethylene and PVC) microplastics affect the microbial communities that form on their surfaces in aquatic environments, finding substantial differences in which bacteria colonized each plastic type and how they processed nitrogen. PLA supported communities rich in nitrogen-cycling bacteria, while PVC and polyethylene enriched different microbial groups associated with pollutant degradation. The study suggests that the push toward biodegradable plastics will change — not just reduce — the ecological effects of microplastics in rivers and lakes.
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