Methods Floating debris items with attached gooseneck barnacles (Fig. 1A) were opportunistically collected during the 2009 Scripps Environmental Accumulation of Plastic Expedition (SEAPLEX) and two 2012 Sea Education Association (SEA) research cruises onboard the SSV Robert C. Seamans: S242, an undergraduate voyage from Honolulu, HI to San Francisco, CA (mid-June to mid-July 2012), and S243, the Plastics at SEA: North Pacific Expedition from San Diego, CA to Honolulu, HI (early October to mid-November 2012). Collection occurred by several means, including (1) from the vessel using a long-handled dip net (335 µm mesh, 0.5 m diameter mouth); (2) incidentally during neuston net (335 µm mesh, 0.5 × 1.0 m mouth) tows at the air-sea interface; and (3) from small boat surveys within 0.5 km of each vessel when sea conditions were calm. No specific permissions were required for these samples, since they were taken in international waters and did not involve protected species. Seven debris items were sampled on SEAPLEX and 29 by SEA (5 during S242 and 24 on S243). Stations within 8.5 km of each other were combined for a total of 19 sampling locations within in the northeastern Pacific Ocean (Fig. 2, Table 1). Figure 1: Barnacles and ingestion microplastic. (A) A dense aggregation of Lepas spp. barnacles growing on a buoy and attached line, collected in October 2012. (B) Basic anatomy of Lepas denoting the capitulum, which includes the body and its enclosing plates, and the peduncle, the muscular stalk that attaches the barnacle to the substrate. (C) Microplastic ingested by an individual barnacle. Figure 2: Ingestion of microplastic by barnacles across the study area. Circles indicate sampling stations and dark fill indicates the proportion of barnacles that had ingested microplastic at each site. Station coordinates, sample sizes, and ingestion proportions are given in Table 1 Station ID Date of collection Latitude (°N) Longitude (°W) Total no. 
 
 barnacles Proportion 
 
 with plastic Proportion 
 
 without plastic S242-021-DN 1-Jul-12 36.135 154.957 5 0.80 0.20 S242-023-DN 2-Jul-12 37.672 152.163 20 0.00 1.00 S243-083-DN 31-Oct-12 27.000 146.782 10 0.00 1.00 S243-069-DN 27-Oct-12 30.057 145.057 15 0.47 0.53 S243-055-057-058-DN 24-Oct-12 30.140 141.220 80 0.68 0.33 S243-051-052-DN 23-Oct-12 30.230 140.690 34 0.18 0.82 U39.F32 15-Aug-09 34.076 140.474 53 0.40 0.60 S243-046-DN 22-Oct-12 31.330 140.338 52 0.42 0.58 S3.F6 10-Aug-09 32.911 140.320 2 0.00 1.00 S242-031-NT 6-Jul-12 39.178 140.160 12 0.00 1.00 S4.F30-F26 14-Aug-09 34.090 139.870 9 0.33 0.67 S242-032-DN 6-Jul-12 39.270 139.570 10 0.10 0.90 S2.F22-U40.F11 9-Aug-09 32.050 137.928 15 0.07 0.93 F13 9-Aug-09 32.075 137.223 1 1.00 0.00 S243-032-DN 16-Oct-12 33.563 135.432 17 0.59 0.41 S242-035-DN 8-Jul-12 39.717 135.325 10 0.00 1.00 S243-025-027-DN 14-Oct-12 33.700 133.460 13 0.00 1.00 S243-023-DN 13-Oct-12 33.051 132.445 14 0.00 1.00 S243-011-DN 9-Oct-12 33.493 127.715 13 0.00 1.00 DOI: 10.7717/peerj.184/table-1 During SEAPLEX, the entire piece of debris with attached barnacles was preserved in 5% Formalin buffered with sodium borate. When the item was too large to be preserved (e.g., a fishing buoy), barnacles were removed and preserved separately. On SEA cruises, as many barnacles as possible to a maximum of 50 were removed from the debris object and preserved in 10% ethanol. Where feasible, a fragment of the item itself was also sampled. In the laboratory, capitulum length was measured using a ruler and species identification (L. anatifera or L. pacifica) determined for all intact individuals (Fig. 1B). Barnacles less than 0.8 cm were present, but not sampled in this study. Barnacles greater than approximately 0.8 cm in length were dissected and the contents of their stomach and intestinal tract examined under a dissecting microscope (6–25 × magnification as needed). Barnacles were cut open with a scalpel, and the intestinal tract removed and placed in a separate section of the petri dish. The intestinal tract was opened lengthwise, and the contents examined systematically both visually and with forceps. To avoid cross-contamination between samples, each barnacle was dissected in a unique, clean petri dish and the scalpel was thoroughly rinsed with deionized water between each samples. Only microplastic fragments and monofilament that were clearly present inside the intestine were considered. Fine microfibers were discounted, as they could not be distinguished from airborne contamination. Because the vast majority of microplastic found were relatively large degraded fragments (>0.5 mm in diameter), visual examination was sufficient to confirm that the microplastic was present in the intestine, and not a result of contamination (Fig. 1C). Plastic particles found in the stomach or intestine were quantified, photographed digitally against a ruler for size assessment, rinsed with fresh water and stored in a glass vial for later analyses. The maximum diameter (feret diameter) and two-dimensional area of each particle were digitally measured with the software package NIH ImageJ (Schneider, Rasband & Eliceiri, 2012). On the SEAPLEX cruise in 2009, we also measured the diameter and area of all plastic particles captured in surface-towed plankton nets (number of particles = 30,518) using NIH ImageJ-based tools in the Zooprocess software calibrated against manual measurements (Gilfillan et al., 2009; Gorsky et al., 2010). We identified the type of plastic recovered from a randomly selected subset of barnacles (Barnacles N = 42; particles N = 219). A Raman spectrometer (PeakSeeker Pro-785 with AmScope operated at 10–50 mW and 5–20 s integration time; Raman Systems MII, Inc/Agiltron, Inc., Woburn, MA) and associated RSIQ software were used to identify plastic type. The Raman spectrum for each plastic piece was compared to a reference library of known plastic types for identification. Particles of clear, white, gray and pale-colored (light blues and greens, oranges and yellows) plastics yielded high quality Raman spectra and were readily identifiable. Those that were darker (medium to dark blues, reds and greens as well as black; 35% of particles subjected to Raman spectroscopy) were heated by the laser beam and melted even at the lowest possible power and integration time settings, resulting in no usable spectra. We also identified a subset of the debris items to which the barnacles were attached. Fragments of 18 objects were collected for analysis, but 6 could not be identified due to darker pigmentation which caused melting under the laser. Statistics and figures were generated with the R statistical environment, version R-2.15.1 (R Development Core Team, 2012) and QuantumGIS, version 1.8.0-Lisboa (QGIS Development Team, 2013). 
 
 Results Of the 385 barnacles examined, 129 individuals (33.5%) had ingested plastic (Fig. 2, Table 1). These included 243 Lepas anatifera and 85 Lepas pacifica (57 barnacles could not be identified to species), of which 90 L. anatifera, 34 L. pacifica, and 5 Lepas spp. contained plastic. Forty-one of the barnacles that ingested plastic had one plastic particle in their stomach or intestines, 26 individuals had two particles, and 57 individuals contained three or more particles, to a maximum of 30 particles (Fig. 3A). Figure 3: Number of microplastic particles ingested by barnacles. (A) Frequency distribution of microplastic pellets ingested by individual lepadid barnacles (N = 385). (B) Frequency distribution of ingestion by capitulum length (N = 369; sample size is smaller than above since capitulum length was not measured for 16 barnacles). Black bars are the number of individual barnacles that ingested plastic and grey bars are the number of individual barnacles that did not ingest plastic. Bins of capitulum length are greater than the first value, and less than or equal to the second value (e.g., >0.5 cm and < = 1.0 cm). Percentages of ingestion by size class are as follows: 6.7%, 0, 23.2%, 43.9%, 45.2%, 35.3%, 25.0%, 40.0%, 0. Overall, the number of ingested particles was positively correlated to capitulum length (Kendall’s tau = 0.099, p = 0.015). However, when we considered only barnacles that had ingested plastic, the correlation between plastic ingestion and capitulum length was not significant (Kendall’s tau = −0.080, p = 0.229). Individuals with a capitulum length between 2 and 3 cm consumed the greatest number plastic particles (Fig. 3B). With the exception of one individual, all the barnacles that consumed plastic had a capitulum length of 1.7 cm or greater. In total, 518 plastic particles were recovered from barnacle digestive tracts. Of these, 99% were degraded fragments and 1% were monofilament line. None of the pre-production pellets known as “nurdles” were found. The median diameter of ingested particles was 1.41 mm, and the median surface area 1.00 mm2, smaller than the median diameter of 1.78 mm and median surface area of 1.27 mm2 for all particles collected in nets during 2009 (Fig. 4, Kolmogorov–Smirnov test p < 0.001). The smallest particle ingested by barnacles had a maximum diameter of 0.609 mm and the largest (a long thin fragment) a maximum diameter of 6.770 mm. No blockage of the stomach or intestine was observed, and particles did not accumulate in any area of the digestive tract. All particles were of a plausible size to pass through the anus. Figure 4: Size of microplastic particles ingested by barnacles. Size–frequency distributions for (A) maximum diameter and (B) two-dimensional surface area of particles ingested by barnacles (black; N = 507) compared to of all microplastic particles collected in 2009 (grey; N = 30,518). Note: 518 microplastic particles were recovered from barnacles, but 11 were lost before they could be photographed for this analysis. Of the randomly selected subset of 219 ingested plastic particles that were analyzed for plastic type, 58.4% were polyethylene, 5.0% were polypropylene, and 1.4% were polystyrene. As noted in the Methods section, we were unable to identify 35% of the subset due to darker pigmentation in these particles, which caused melting under the Raman spectrophotometer. Of the 29 barnacles that had ingested more than one piece of plastic, 66% contained more than one type of plastic. The plastic types of 12 floating debris items to which barnacles were attached were more diverse than those of ingested particles. Four substrates were polystyrene, 3 were polyethylene, 2 were polypropylene, 2 were polyethylene terephthalate, and one was tire rubber. ||||| Plastic litter dots the surf line on a beach on the island of Hawaii. 
 
 Credit: Stephanie Pappas for LiveScience View full size image 
 
 The oceans are full of plastic. Now, research finds that even barnacles are feeling the consequences. 
 
 A third of barnacles caught in the North Pacific gyre, a region of the ocean notoriously littered with scraps of plastic, have microfragments of the plastic material in their digestive systems at a given time, a new study finds. Researchers aren't sure whether ingesting the non-food harms the barnacles, but it could crowd out real nutrition. 
 
 Plastic debris is a major problem in the oceans, particularly when sea life becomes entangled in the garbage or ingests it. At least 267 marine species have been documented eating plastic, including turtles, fish and birds, researchers report today (Oct. 22) in the open-access journal PeerJ. 
 
 The North Pacific gyre is so heavily laden with plastic that it's earned the nickname, "The North Pacific Garbage Patch." Here, Miriam Goldstein of the Scripps Institution of Oceanography in California and Deborah Goodwin of the Sea Education Association in Woods Hole, Mass., tested an unknown question: Are marine invertebrates, such as barnacles and other animals without backbones, also consuming plastic garbage? 
 
 Laboratory studies suggested filter feeders like barnacles do pick up plastic pellets, but only three examples of plastic-eating invertebrates were known in the wild. (Sandhopper amphipods, or sand fleas, the Norway lobster and flying squid, for those keeping score.) 
 
 The researchers collected barnacles of two species, Lepas anatifera and Lepas pacifica, on two separate trips to the gyre. They then conducted barnacle autopsies, checking the digestive systems of the animals for microplastics, or plastic pieces worn by wind and waves to less than 0.2 inches (5 millimeters) in diameter. 
 
 Of the 385 barnacles collected, 129 had ingested plastic, the researchers found. Most of those individuals had a pellet or two in their gut, but 57 had more than three pieces, with one containing a whopping 30 individual plastic particles. 
 
 Researchers aren't sure whether these particles are affecting the barnacle's health; there were no signs of digestive backup in this group, at least. The long-term effects are unknown, they wrote. 
 
 Unfortunately for the oceans, this tendency for barnacles to eat plastic doesn't help remove the litter permanently. 
 
 "The barnacles just poop out the plastic & it floats away again," Goldstein wrote on Twitter. 
 
 Follow Stephanie Pappas on Twitterand Google+. Follow us @livescience, Facebook & Google+. Original article on LiveScience.
– Today's most unfortunate number: 267. That's the number of marine species that have been found to have eaten plastic, and a new study zeroes in on one such species— barnacles. Researchers traveled to the North Pacific Gyre (better known as the Great Pacific Garbage Patch) with a question: Are marine invertebrates eating plastic trash, too? LiveScience explains that the knowledge on the subject was fairly limited, with lab studies indicating the answer is "yes," but field research having revealed only three backbone-less species known to consume it. And so researchers gathered 385 barnacles and zeroed in on their gastrointestinal tracts ... and found something there. "Microplastics," which LiveScience defines as small pieces winnowed down by the elements to sizes of less than 0.2 inches. Such particles were present in 33.5% of the barnacles' tracts; 44% of those had more than three particles there. So what does this mean? "The implications ... remain uncertain," write the study authors. They found no evidence of stomach or intestinal blockage, but the possibility exists that the particles could have an effect on barnacles' nutrition. What it won't have an effect on, notes LiveScience: the amount of plastic in the ocean. What barnacles eat, they eventually "poop out."