Microplastic and microfiber pollution has been documented in all major ocean basins. Microfibers are one of the most common microparticle pollutants along shorelines. Over 9 million tons of fibers are produced annually; 60% are synthetic and ∼25% are non-synthetic. Non-synthetic and semi-synthetic microfibers are infrequently documented and not typically included in marine environment impact analyses, resulting in underestimation of a potentially pervasive and harmful pollutant. We present the most extensive worldwide microparticle distribution dataset using 1-liter grab samples (n = 1393). Our citizen scientist driven study shows a global microparticle average of 11.8 ± 24.0 particles L (mean ± SD), approximately three orders of magnitude higher than global model predictions. Open ocean samples showed consistently higher densities than coastal samples, with the highest concentrations found in the polar oceans (n = 51), confirming previous empirical and theoretical studies. Particles were predominantly microfibers (91%) and 0.1-1.5 mm in length (77%), a smaller size than those captured in the majority of surface studies. Using μFT-IR we determined the material types of 113 pieces; 57% were classified as synthetic, 12% as semi-synthetic, and 31% as non-synthetic. Samples were taken globally, including from coastal environments and understudied ocean regions. Some of these sites are emerging as areas of concentrated floating plastic and anthropogenic debris, influenced by distant waste mismanagement and/or deposition of airborne particles. Incorporation of smaller-sized microfibers in oceanographic models, which has been lacking, will help us to better understand the movement and transformation of synthetic, semi-synthetic and non-synthetic microparticles in regional seas and ocean basins.

Abstract. Although the influence of regional processes on local patches is well studied, the influence of local patches and their spatial arrangement on regional processes is likely to be complex. One interesting idea is the keystone community concept (KCC); this posits that there may be some patches that have a disproportionately large effect on the metacommunity compared to other patches. We experimentally test the KCC by using replicate protist microcosm metacommunities with single-patch removals. Removing single patches had no effect on average community richness, evenness and biomass of our metacommunities, but did cause metacommunities to be assembled significantly less by local environmental conditions and more by spatial effects related to stochastic factors. Overall our results show that local patch removal can have large regional effects on structural processes, but indicate that more experiments are needed to find evidence of keystone communities.

Microplastic and microfiber pollution has been documented in all major ocean basins. Microfibers areone of the most common microparticle pollutants along shorelines. Over 9 million tons of fibers areproduced annually; 60% are synthetic and ~25% are non-synthetic. Non-synthetic and semi-syntheticmicrofibers are infrequently documented and not typically included in marine environment impactanalyses, resulting in underestimation of a potentially pervasive and harmful pollutant. We present themost extensive worldwide microparticle distribution dataset using 1-liter grab samples (n ¼ 1393). Ourcitizen scientist driven study shows a global microparticle average of 11.8 ± 24.0 particles L?1(mean ± SD), approximately three orders of magnitude higher than global model predictions. Open oceansamples showed consistently higher densities than coastal samples, with the highest concentrationsfound in the polar oceans (n ¼ 51), confirming previous empirical and theoretical studies. Particles werepredominantly microfibers (91%) and 0.1e1.5mm in length (77%), a smaller size than those captured inthe majority of surface studies. Using mFT-IR we determined the material types of 113 pieces; 57% wereclassified as synthetic, 12% as semi-synthetic, and 31% as non-synthetic. Samples were taken globally,including from coastal environments and understudied ocean regions. Some of these sites are emergingas areas of concentrated floating plastic and anthropogenic debris, influenced by distant wastemismanagement and/or deposition of airborne particles. Incorporation of smaller-sized microfibers inoceanographic models, which has been lacking, will help us to better understand the movement andtransformation of synthetic, semi-synthetic and non-synthetic microparticles in regional seas and oceanbasins.

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