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 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 

Microplastics in the marine environment

I've been researching microplastic (MP) presence and abundance for about two years now. It is interesting to see how these particles smaller than 5 mm in diameter or length are ubiquitous in the marine environment. After doing some research, we found MPs in different molluscs, fish and even in marine otter scats from the coast of Peru. Determining the exact sources is quite hard, but it is most likely that the poor waste water treatments promote the dispersal of microfibers (which are, by the way, the most common MP morphological type I've found here and many studies agree with this).

Fig. 1. Blue microfibers found in the stomach of Cheilodactylus variegatus from the coast of Lima, Peru

The MPs in figure 1 are about larger than 100um. I'm looking forward to investigate MP bioaccumulation in Peruvian bivalves through the correlation between MP content and valve length and wet weight of each individual. It sound very interesting to me.