Microplastic ingestion in Otariids

Transportation of microplastics along the food chain is no surprise. Trophic transfer from prey to predators is a fairly common source of microplastics, especially in top predators. A recently published research by Perez-Venegas et al. (2020) evidenced the ingestion of microplastics in Otariids from the coast of Chile and Peru by analyzing their scats.

Fig. 1. Arctocephalus sp. 

As reported in the study, the occurrence of micro-fibres (ranging from 63 to 100%) was much bigger than fragments (1 to 14%). Higher concentrations in samples from the Juan Fernández Archipielago may be due to the influence of the South Pacific subtropical gyre, an area of high plastic debris concentration. The presence of these particles can potentially be harmful to these animals, although this requires further research.

Reference
Perez-Venegas, D.J., Toro-Valdivieso, C., Ayala, F., Brito, B., Iturra, L., Arriagada, M., Seguel, M., Barrios, C., Sepúlveda, M., Oliva, D., Cárdenas-Alayza, S., Urbina, M.A., Jorquera, A., Castro-Nallar, E., Galbán-Malagón, C., 2020. Monitoring the occurrence of microplastic ingestion in Otariids along the Peruvian and Chilean coasts. Mar. Pollut. Bull. 153, 110966. https://doi.org/10.1016/j.marpolbul.2020.110966

How much micro- and mesoplastics can seaweed retain?

During a microplastic sampling campaign in Lima, Perú, we noticed in an extremely polluted beach, seaweed inhabiting intertidal rock formations were retaining high amounts of micro- and mesoplastics (Fig. 1, 2).

Fig. 1. First photo of microplastics retained in seaweed in a sandy beach of Lima, Perú

Fig. 2. Second photo of microplastics retained in seaweed in a sandy beach of Lima, Perú

It is noticeable that MPs are trapped in seaweed formations, rather than rock surface. A question comes: How much MP and mesoplastic can seaweed retain under extreme pollution conditions? 

We are looking forward to do some research regarding these observations. 

Commercial bivalves contaminated with microplastics in Peru

The mussel Aulacomya atra, also known as "choro", is one highly consumed bivalve species of commercial importance. The second most consumed after the Peruvian scallop Argopecten purpuratus. A. atra is commonly served fresh and eaten as a whole, thus presenting a higher chance of microplastic ingestion. 

We investigated the abundance and characteristics of microplastics in A. atra from fishery markets in three Peruvian provinces: Huarmey, Lima and Pisco (Fig. 1). 

Fig.1 Map of the three Peruvian provinces. S1: Huarmey, S2: Lima and S3: Pisco

Results indicated that microplastics were ubiquitous in A. atra from fishery markets. Microplastics of different sizes, shapes and colors were found and recorded (Fig. 2).

Fig. 2 Microplastics found in A. atra. A: Red microbead, B: Blue fiber, C: White fragment, D: Green line, and E: White film. Scale bar indicated 1 mm.

This is the first evidence of microplastic contamination in A. atra. The presence of microplastics in the last step of the supply chain confirms that the Peruvian population are subject to microplastic intake through contaminated seafood. Further research must continue surveying markets and fishery markets aiming to contribute to the microplastic human intake estimation. 

This manuscript is currently under review by the Journal of Food Science and Technology, once it gets published, I will make sure to share the research entirely. Questions regarding this research, feel free to send me an email: gabriel.e.dltp@gmail.com 

Microplastic distribution in sandy beaches of Lima, Peru

In a research we conducted two years ago (and have been recently accepted in the Marine Pollution Bulletin), assessing larger microplastic (1-5 mm) abundance in the intertidal (ITZ) and supralittoral zone (SLZ) in four sandy beaches (Yuyos, Sombrillas, Agua Dulce and Pescadores) of Lima (Fig. 1), we found very strange results.

Fig. 1. Map showing the region and the sites selected in the coast of Lima. S1: Yuyos, S2: Sombrillas, S3: Agua Dulce, and S4: Pescadores. Black squares above the high tide line indicate the orientation of the transects from the supralittoral zone and below the transect from the intertidal zone.

The microplastic (MP) concentrations varied considerably but, in general terms, our main issue was finding larger amounts of MPs in the ITZ in the two most polluted beaches (See Fig. 2 for a reference of the magnitude). Trying to explain why was hard. Superficial current did not make much influence as we assessed a very small area (the four beaches were very close to each other. 

Fig. 2 Boxplot of the microplastic abundance (particles m-2) per beach and beach zone. SLZ: Supralitoral zone, and ITZ: Intertidal zone

Reduced tidal action was observed in Yuyos and Pescadores, as they were highly influenced by artificial structures, like intertidal breakwaters. Aguilera et al. (2016) revealed that these structures promote retention and accumulation of human derived litter, including the entrapment of floating debris. This is one factor to understand the lack of washed up microplastics in this two beaches.
However, the extremely high abundance in Sombrillas and Agua Dulce may be do to something else. Something we should highlight is that the vast majority of the overall microplastics found in the four beaches were foams (78.3%), which is another very unusual result, as literature report fibers or fragments as the most common microplastics in sandy beaches. Also, the majority of the foams did not show weathering conditions, like coloring and degrade. We concluded that the high abundance of foams (determined PS after FTIR analysis) was due to the disposal of styrofoam materials (cups, plates, and other stuff) around the beach by beachgoers, provided by many local food businesses within Sombrillas and Agua Dulce. During the summer season, recreational beaches, like Sombrillas and Agua Dulce are overcrowded with people who make an inappropriate disposable of these materials or just bury them in the sand. 

Our article is currently accepted but not yet published. Once it goes online, I will share it with whoever requests it on ResearchGate. 

References

Aguilera MA, Broitman BR, Thiel M (2016) Artificial breakwaters as garbage bins: Structural complexity enhances anthropogenic litter accumulation in marine intertidal habitats. Environ Pollut 214:737-747. doi:10.1016/j.envpol.2016.04.058

How to extract microplastics from fish guts

Some months ago we investigated the microplastic concentration in three commercial fish from the coast of Lima, Peru (De-la-Torre et al., 2019). In general terms, our results indicated that carnivore fish accumulate more microplastics than planktivore fish. This suggests that microplastics could biomagnify along the food chain, as previous results researching the common prey of these species, like chitons and intertidal bivalves, contained microplastics in their soft tissues. 

Indeed, some interesting results, although more and broader research is needed.

The method used to assess microplastic abundance in fish guts followed a simple procedure, as described in Fig. 1. 

Fig. 1. Procedural steps for extracting microplastics from fish guts

Stomach and intestines were extracted and placed in 25 ml glass screw cab test tubes and filled with 10% (w/v) potassium hydroxide (KOH), shaken for a few seconds and heated at 60 °C over 24 h. Following digestion, the supernatant solution was vacuum filtrated through a 20 – 25 µm pore glass fiber filter paper (Whatman) in an 8 cm in diameter porcelain Büchner funnel. Finally, filters must be observed under a stereomicroscope. 

It is absolutely necessary to conduct quality control measures. In this case, all glass and other materias must be rinsed twice or thrice with distillated/Ultrapura/deionized water. Cotton lab coats and gloves must be worn at all times and surfaces must be wiped clean. If possible, conducting the procedure under a fumehood. Quality assurance by having an airborne procedural blank by placing a wet filter on a petri dish for as long as the duration of the laboratory analysis and scan it under a stereomicrospe. The number of airborne microfibers contaminating the blank must not exceed 2 MP/blank. Also, 10% KOH alone must be vacuum filtrated and scanned to determine external contamination reached the KOH. 

References

De-la-Torre, G.E., Dioses-Salinas, D.C., Pérez-Baca, B.L. & Santillán, L. (2019). Microplastic abundance in three commercial fish from the coast of Lima, Peru. Brazilian Journal of Natural Sciences, 2(3), 171-177. https://doi.org/10.31415/bjns.v2i3.67 

Plasticrusts: A new potential threat in the Anthropocene's rocky shores

The new term 'plasticrusts' have been coined in a recent article published in Science of the Total Environment by Gestoso et al. (2019). This type of plastic pollution refers to plastic pieces of blends encrusting the texture of intertidal rocks forming crusts that could vary in color and forms.

Fig. 1. Pictures showing (A, B) a general overview of mid-upper intertidal rocky shore in Madeira Island encrusted by plastic; (C) detail of ‘plasticrusts’ on the surface of the rocks; and (D, E) view of ‘plasticrusts’ surrounded by the littorinid gastropod Tectarius striatus.

Plasticrusts could expose marine rock grazers, like gastropods, to plastic debris ingestion. This type of plastic pollution could be considered as a new litter category for monitoring guidelines.

Reference
Gestoso, I., Cacabelos, E., Ramalhosa, P., & Canning-Clode, Joao. (2019). Plasticrusts: A new potential threat in the Anthropocene's rocky shores. Science of The Total Environment, 687, 413-415. https://doi.org/10.1016/j.scitotenv.2019.06.123

Amberstripe scads ingest microplastics resembling their copepod prey

A research published in 2017 aimed to compare the size and color of microplastics and copepod species found in surface waters and in the digestive tract of Decapterus muroadsi captured along the coast of Rapa Nui. 

Although the majority of the microplastics in the medium (surface water) were orange, a high abundance of blue microplastic fragments were found in D. muroadsi digestive tracts. Statistical analysis indicated a significantly different selectivity among microplastics of the four colors found in the water samples. This confirmed a selectivity for blue microplastics.

Fig. 1. Size-frequency distribution (% of the total number) of microplastics (bars) of the four colors most frequently found in the 6 superficial water samples (195 microplastics in total; 6 black, 3 grey, 2 red, 2 yellow, 1 purple and 1 green particles are not shown here) and in the 16 fish that had ingested at least one microplastic (45 microplastics; 2 black and 1 green particles are not shown here). Size distributions of three blue-pigmented copepod species (scatter plots) found in the water samples and in the 20 fish that ingested copepods are shown. 

This study suggests that some fish could mistakenly ingest microplastics resembling their natural prey. 

Fig. 2. Examples of (a–f) blue microplastics in D. muroadsi digestive tracts, and (g) copepod prey Pontella sinica male, (h) Sapphirina sp. and (i) Corycaeus sp. in superficial water along the

coast of Rapa Nui (Easter Island). Scale bars represent 0.5 mm.

For further reading, check the references for the link to the full article.

References

Ory, N. C., Sobral, P., Ferreira, J. L., & Thiel, M. (2017). Amberstripe scad Decapterus muroadsi (Carangidae) fish ingest blue microplastics resembling their copepod prey along the coast of Rapa Nui (Easter Island) in the South Pacific subtropical gyre. Science of the Total Environment, 586, 430–437. https://doi.org/10.1016/j.scitotenv.2017.01.175