By Delaney Reynolds, SRC intern
Plastic pollution has become one of the largest adverse impacts on marine life to date. In the last 70 years, plastic debris has become so prominent in layers of sedimentary deposits that it can be used as a primary indicator for the Anthropocene, a human-induced geological epoch (Puskic, et al. 2019). While plastic does technically break down, it only fragments into micro- and nano-plastics and thus never leaves the environment completely. These miniscule particles are commonly consumed by marine animals of all sizes ranging from plankton to whales. Seabirds such as albatross, petrels, and shearwaters have been found to have very high plastic ingestion rates due to their foraging strategies, as well as its various colors and odors that they find attractive. Ingesting plastic debris causes damage to lipid-derived fatty acids (FAs). FAs are warehoused in a variety of tissues for energy storage. Adipose tissues, connective tissue that also stores energy in the form of fat, contains triglycerides (TAG), main constituents in body fats, which are a vital energy source for juvenile birds.
Researchers from the Institute for Marine and Antarctic Studies at the University of Tasmania explored how FA analysis could be used to investigate the impacts of seabird plastic ingestion on seabirds’ health. Roadkill or beach-washed deceased flesh-footed shearwater and short-tailed shearwater fledglings were collected on Lord Howe Island, New South Wales, Australia. Their body mass, wing length, and head + bill length were measured and plastic debris less than one millimeter in size were weighed. Adipose tissues were collected from breasts and FAs were extracted and analyzed with several statistical tests. The average number of plastic debris ingested was found to be 4.47 pieces weighing approximately 0.0760 grams for short-tailed shearwaters. The average number of plastic debris ingested was found to be 18.44 pieces weighing approximately 2.9277 grams for flesh-footed shearwaters. Although the research did not find a significant relationship between the mass of plastic, number of plastic debris present, and body mass, 37 different FAs were found in liver and muscle tissues between both species (Puskic, et al. 2019).
Discrepancies found between the FAs identified in the different species of shearwaters may be attributed to the turnover rate of FAs and lipid classes specific to tissues. The study concluded that flesh-footed and short-tailed shearwaters are, indeed, two distinct groups of one species based on FA composition. The FA composition of prey species likely drives the difference, as flesh-footed shearwaters are known to feed on mesopelagic fish and squid and short-tailed shearwaters are known to feed on krill and small cephalopods. These two different classes of prey have dramatically different FA levels, and this was found to be reflected in the FA outputs of the two different shearwaters.
Based on this study, fatty acid analysis can be used to explore how plastic pollution disrupts nutritional pathways and it was found that within the sample of shearwaters collected, there was no effect. These types of studies and tools will be imperative for use to manage and analyze the current and future effects of plastics on other species, especially marine, as anthropogenic-driven plastic pollution continues to become more prevalent in our world.
Puskic, Peter S, et al. “Uncovering the Sub-Lethal Impacts of Plastic Ingestion by Shearwaters Using Fatty Acid Analysis.” Conservation Physiology, Oxford University Press, 16 May 2019, academic.oup.com/conphys/article/7/1/coz017/5489824.