Microplastics in Cetaceans Stranded on the Portuguese Coast

Abstract

This study characterises microplastics in small cetaceans on the coast of Portugal and assesses the relationship between several biological variables and the amount of detected microplastics. The intestines of 38 stranded dead cetaceans were processed in the laboratory, with digestion methods adapted to the amount of organic matter in each sample. The influence of several biological and health variables (e.g., species, sex, body condition) on the amount of microplastics was tested in all analysed species and particularly in common dolphins, due to the larger number of available samples. Most of the analysed individuals had microplastics in the intestine (92.11%), with harbour porpoises revealing a significantly higher median number of microplastics than common dolphins, probably due to their different diets, use of habitat and feeding strategies. None of the other tested variables significantly influenced the number of microplastics. Moreover, the microplastics found should not be enough to cause physical or chemical sublethal effects, although the correlation between microplastic ingestion and plastic additive bioaccumulation in cetacean tissues requires further investigation. Future monitoring in biota should rely on improved and standardised protocols for microplastic analyses in complex samples to allow for accurate analyses of larger samples and spatio-temporal comparisons.

Preliminary Study on Microplastic Contamination in Black Sea Cetaceans: Gastrointestinal Analysis of Phocoena phocoena relicta and Tursiops truncatus ponticus

“…In our investigation, we found microplastic particles in all the analysed samples. A frequency of occurrence (FO%) of 100% is in line with most of the available studies [ 30 , 35 , 38 , 39 , 40 , 41 ].…”

“…Of the 18 particles found, 14 items were found in the procedural blank, and 4 items in the controls. Microplastic items with the same characteristics as the items found on the blanks were excluded from the database [ 30 ].…”

“…Because of the large variation in the number of microplastic items identified in the two studies, the comparison needs to be carefully considered. Anyway, in terms of ingested plastic quantity, comparisons between studies are challenging because of differences in GIT compartments analysed and the methodology followed [ 30 ]. In addition to the already mentioned factors, there could be other variables that can influence the number of ingested microplastics [ 38 ].…”

“…Procedural blanks were taken before washing the GIT, and control samples were maintained throughout the activity. All particles found ( n = 18) in procedural blanks and controls were removed from the study’s database in a 1:1 ratio to uphold data integrity [ 30 ].…”

“…Cetaceans interact with microplastics through direct ingestion from the environment or through trophic transfer. Although there are several studies available for other regions [ 25 , 26 , 27 , 28 , 29 , 30 ], in the Black Sea, the topic is still largely unexplored. The lack of information is mostly attributed to limited research endeavours.…”