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Caption : figure si.1. a – research-grade ntio<sub>2</sub> nanopowder purchased from sigma aldrich; b – ntio<sub>2</sub> extracted from skinceuticals™ sunscreen (s1); c – ntio<sub>2</sub> extracted from boots soltan™ sunscreen (s2); di and dii – ntio<sub>2</sub> extracted from the body shop™ liquid foundation (p1). left panel shows scanning transmission electron microscope image of samples; other panels show false coloured eds image of element as labelled. 


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Caption : figure si.2. powder x-ray diffraction patterns of samples, with anatase (a) and rutile (r) planes indexed to jcpds card numbers 21-1272 and 21-1276 for the tetragonal structures of anatase and rutile tio2, respectively, as labelled. peaks at 11.5°, 17.2°, 21.6°, 24.1°, 24.6°, 27.8°, 30.1°, and 30.7° can be indexed to the (101), (004), (200), (105), (211), (118), (116), and (220) planes of the tetragonal anatase crystal system. major peaks observed at 12.5°, 16.4°, 18.7°, 24.2°, 25.1°, 27.8°, 28.2°, and 30.1° can be indexed to the (110), (101), (111), (211), (220), (002), (310), and (301) planes of rutile tio<sub>2</sub>. 


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Caption : figure si.3. total event count obtained from flow cytometric analysis of cell-free ntio<sub>2</sub> suspensions in natural seawater.

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Caption : figure si.4. photographic observation of sedimentation of ntio<sub>2</sub> triplicate samples during dls analysis; a/ai – 24 h, b/bi – 168 h, c/ci – 240 h, d/di – 336 h.

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Caption : figure si.5. volcano plot of cellular (a) and extracellular (b) proteomes. red symbols indicate where t-tests identified proteins to significantly vary between control and ntio<sub>2</sub> treated cultures (p<0.05).


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Caption : figure si.6. relative abundance of protein groups, classified in terms of biological function as listed on the uniprot database and kegg assignment, identified by proteomic analysis of; a) cellular and b) extracellular samples of prochlorococcus sp. med4 exposed to research-grade ntio<sub>2</sub> (100 μg l-1) for a period of 24 h. data is presented as the mean of three biological replicates.

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Caption : figure si.7. relative abundance of major prokaryotic phyla in each treatment as identified by 16s rrna amplicon sequencing.

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Caption : figure si.8. relative abundance of major eukaryotic phyla in each treatment as identified by 18s rrna amplicon sequencing.