All sample processing (extraction and picking) was conducted in a clean laboratory, where extreme care was taken to avoid any contamination. Checks for contamination during processing were made by exposing damp filter paper to the air in the laboratory, whenever samples were open to the laboratory environment. As an additional precaution, those handling the samples wore only natural fibre clothing, and were protected with 100% cotton laboratory coats and headwear, and latex gloves, for all laboratory processing and during the JC76T research cruise.
Microplastics were extracted from the sediment using two methodologies. For samples 1, 2 and 4–9, extraction was done by Plymouth University (PU) using a concentrated NaCl solution and filtering with three sequential extractions [5 (link)]. The PU method employs supernatant filtering through a Whatman GF/A filter. For samples 3 and 10–12, particle extraction was conducted at the Natural History Museum (NHM) using an adapted Ludox-TM 40 extraction method [15 ] employing eight centrifuge cycles and a 32 μm sieve to separate the microplastics from the sand grains. The substances chosen to isolate the fibres (NaCl or Ludox-TM 40) had similar specific gravities, namely 1.2 and 1.16, for PU and NHM, respectively. We are therefore confident that the same fractions and types of microplastics were isolated.
Using an entomological pin, microplastic fibres from coral specimens 13–16 were removed under a binocular microscope and placed into clean vials containing Millipore water. The fibres were not extracted quantitatively. The corals were of different sizes, and not all fibres present on the corals were removed, therefore just the presence or absence of microplastic accumulation on living coral was recorded.
All sediment samples were examined under a binocular microscope, and any objects that were of unnatural appearance based on shape and colour (potential microplastics) were transferred to sealed containers and subsequently identified [5 (link)] by spectrometry.
Microplastics were extracted from the sediment using two methodologies. For samples 1, 2 and 4–9, extraction was done by Plymouth University (PU) using a concentrated NaCl solution and filtering with three sequential extractions [5 (link)]. The PU method employs supernatant filtering through a Whatman GF/A filter. For samples 3 and 10–12, particle extraction was conducted at the Natural History Museum (NHM) using an adapted Ludox-TM 40 extraction method [15 ] employing eight centrifuge cycles and a 32 μm sieve to separate the microplastics from the sand grains. The substances chosen to isolate the fibres (NaCl or Ludox-TM 40) had similar specific gravities, namely 1.2 and 1.16, for PU and NHM, respectively. We are therefore confident that the same fractions and types of microplastics were isolated.
Using an entomological pin, microplastic fibres from coral specimens 13–16 were removed under a binocular microscope and placed into clean vials containing Millipore water. The fibres were not extracted quantitatively. The corals were of different sizes, and not all fibres present on the corals were removed, therefore just the presence or absence of microplastic accumulation on living coral was recorded.
All sediment samples were examined under a binocular microscope, and any objects that were of unnatural appearance based on shape and colour (potential microplastics) were transferred to sealed containers and subsequently identified [5 (link)] by spectrometry.
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