Whale, what do we have here? Evidence of microplastics in top predators: analysis of two populations of Resident killer whale fecal samples.

Abstract

Environmental microplastics (plastic particles less than 5 mm in size) are a growing ecological issue and are widely documented in marine life. The consequences of microplastic ingestion in top predators are poorly understood but may include physiological and toxicological effects, and the potential for bioaccumulation in apex predators has been suggested. Here, I investigate the presence of microplastics in two populations of North Pacific Resident killer whales and determine if there is a significant difference in the number of microplastics between the populations. This study examined 33 feces samples, 18 from the Southern Resident population, and 15 from the Alaskan Resident population. We implemented multiple contamination-control measures to reduce sample contamination from synthetic clothing and plastic equipment. Microplastics were found in every fecal sample except one, with an average and standard deviation of 82.5 (173) per sample. I observed no significant difference in the number of microplastics between the two populations (p-value = 0.799). Preliminary Raman microspectroscopy revealed three plastic polymer types that included polyethylene, nylon, and polyamide. Verified microplastics were found in fecal samples from both populations of resident killer whales, validating the occurrence of microplastic pollution in upper-trophic marine predators. This study is another example of the pervasiveness of microparticles in the marine environment, and the need for a better understanding of the potential effects on apex predators.