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Patterns of suspended and salp‐ingested microplastic debris in the North Pacific investigated with epifluorescence microscopy

Limnology and Oceanography Letters 2019 113 citations

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Researchers modified epifluorescence microscopy methods to quantify mini-microplastics smaller than 333 micrometres from filtered seawater and salp stomach contents in the North Pacific, finding concentrations 5-7 orders of magnitude higher than those reported for larger microplastics. Every salp examined had ingested mini-microplastics regardless of species or oceanic region, and salps selectively ingested smaller plastic particles than were available in the surrounding water.

Body Systems
Study Type Environmental

Abstract Microplastics (< 5 mm) have long been a concern in marine debris research, but quantifying the smallest microplastics (< 333 μ m) has been hampered by appropriate collection methods, like net tows. We modified standard epifluorescence microscopy methods to develop a new technique to enumerate < 333 μ m microplastics (mini‐microplastics) from filtered surface seawater samples and salp stomach contents. This permitted us to distinguish mini‐microplastics from phytoplankton and suspended particles. We found seawater mini‐microplastic concentrations that were 5–7 orders of magnitude higher than published concentrations of > 333 μ m microplastics. Mini‐microplastics were the most abundant in nearshore waters and more evenly distributed from the California Current through the North Pacific Subtropical Gyre. Every salp examined had ingested mini‐microplastics, regardless of species, life history stage, or oceanic region. Salps ingested significantly smaller plastic particles than were available in ambient surface seawater. The blastozooid stage of salps had higher ingestion rates than oozooids.

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