DOI: 10.5061/dryad.mpg4f4qtr
title: Microplastic contamination in Corpus Christi Bay blue crabs, Callinectes sapidus

description: Microplastic pollution has been observed in marine environments around the
 world and has the potential to negatively impact marine organisms when
 ingested. One organism of particular concern is the blue crab, Callinectes
 sapidus, whose feeding strategies increase their likelihood of exposure to
 plastic pollution. To assess microplastic contamination in blue crabs, 39
 individuals were collected from Corpus Christi Bay, TX and processed using
 a hydrogen-peroxide based tissue destruction method followed by
 confirmation using micro-attenuated total reflectance Fourier transform
 infrared spectroscopy (µ-FTIR). From the 39 blue crabs sampled, 28 fully
 synthetic fragments and fibers and 24 semi-synthetic fibers were found
 within their stomachs. After correcting for possible contamination, 36% of
 collected blue crabs were estimated to contain 20 synthetic fragments and
 fibers and 14 semi-synthetic fibers (0.87 items crab-1). This study shows
 that blue crabs ingest microplastic items in Corpus Christi, TX and
 populations in other locations likely face similar risks.
description: Microplastic ingestion by blue crabs was assessed by collecting
 specimens from three sites around Corpus Christi Bay. A total of 39 blue
 crabs were collected (12 from Site A, 15 from Site B, and 12 from Site C)
 using lines baited with raw chicken. Blue crabs were transported to the
 lab in a hard-plastic cooler with a polyethylene exterior and
 polypropylene interior. Travel time from the sampling location to the lab
 varied from 15-45 minutes.  Upon returning to the lab, the length, mass,
 and sex of the crabs were recorded. Blue crabs were then chilled to numb
 their senses and euthanized humanely before their stomachs were collected
 and individually placed into clean 15 ml scintillation vials. 
 Blue crab
 stomachs were isolated and placed in a clean 50 mL centrifuge tube,
 loosely sealed with a cap, and dried at 40 °C for 7 days. Then the
 stomachs were gently crushed with a glass stirring rod to increase the
 tissue surface area. To ensure no materials remained on the rod, it was
 rinsed three times into the centrifuge tube with 2 mL of 30 %
 H<sub>2</sub>O<sub>2</sub>, for a total of 6 mL.
 The glass stirring rod was then visually inspected under a
 stereomicroscope to ensure no materials remained attached. Samples were
 then loosely recapped and digested overnight at 20 °C before the addition
 of another 2 mL of 30 % H<sub>2</sub>O<sub>2</sub>
 followed by gentle swirling for 15 seconds. This digestion step was
 repeated twice, using a total of 6 mL more over 72 hours, before the
 centrifuge tubes digested at 20 °C for a final 48 hours. Next, the
 centrifuge tubes were heated at 40 °C in a hot water bath for 2 hours
 before vacuum filtration through a 0.8 µm cellulose acetate membrane
 filter. The filtering apparatus and now-empty centrifuge tube were
 inspected under a microscope to ensure the complete transfer of material.
 Filters were then visually inspected under a stereomicroscope for
 suspected microplastic materials. Suspected
 microplastic particles and fibers extracted from blue crabs were analyzed
 using µ-FTIR on a Thermo Nicolet iS10 FTIR equipped with a mercury cadmium
 telluride infra-red detector and a iN5 Microscope with a germanium crystal
 for attenuated total reflectance. Sample spectra were collected with 256
 scans at a resolution of 8 cm <sup>-1 </sup>over the range of
 650 - 4000 cm<sup>-1</sup>. Backgrounds were collected before
 each sample run and all collected spectra were compared to the “Forensic
 Comprehensive”, “HR sprouse polymers by ATR”, “ICHEM Nicodom ATR, ATR 100
 Specta Dema Library”, and “Hummel polymer sample library” databases for
 identification. Samples that positively matched the database (&gt;65%
 confidence) were included in the results. All glassware
 and utensils were washed with detergent and subsequently  rinsed with DI
 water prior to use. Glassware was muffled at 500 °C for 4 hours and
 covered with aluminum foil after cooling. Utensils and glassware were
 inspected under a microscope prior to use. Laboratory contamination of
 samples was assessed by running a method blank, a pre-cleaned empty vial
 that was identically processed alongside the samples at a rate of one for
 every three samples. Each blank was exposed to the same conditions and
 manipulation as its paired samples, and was, once processed and filtered,
 left open for the duration of the microscope analysis of the paired
 samples to assess the possible contamination during this step. In this
 way, the method blanks were exposed to the same laboratory conditions for
 the same duration as the three samples they were paired with.  Sample
 contamination from laboratory sources was assessed by establishing limits
 of detection (LOD), which is the mean plastic contamination from sample
 blanks + 3× Standard deviation, for each type of plastic (based on
 coloration, shape, and material) observed in these method blanks (De Witte
 et al., 2014).
description: Table 1, tab 1 of  the spreadsheet 'Compiled dataset of
 microplastics and fibers recovered from Corpus Christi blue crabs',
 describes the physical features (fiber, fragmnet, or film) and coloration
 of items suspected to be synthetic fibers, fragments, or films as observed
 in the processed blue crab stomachs. Items detailed in table 1 are
 considered "suspected" plastics as no identification via FTIR
 had yet to be performed. Table 2, tab 2 of  the
 spreadsheet 'Compiled dataset of microplastics and fibers recovered
 from Corpus Christi blue crabs', describes the physical
 features (fiber, fragment, or film) and coloration of items confirmed via
 micro-FTIR to be plastic or sem-synthetic as observed in the processed
 blue crab stomachs. Table 3, tab 3 of  the spreadsheet
 'Compiled dataset of microplastics and fibers recovered from Corpus
 Christi blue crabs', describes the composition of plastic or
 semi-synthetic items recovered from blue crab stomachs.