Distribution and toxicology of plastic in the Tasman Sea: implications for Australia’s flesh-footed shearwaters (Ardenna carneipes)

The ever-increasing manufacture, consumption and disposability of plastic products has made them ubiquitous in today’s society. Many plastic items play an important role in daily activities. However, unfortunately, due to an excess of these materials used for single-use packaging, combined with an inefficient disposal system, they are omnipresent in the natural environment. Plastics frequently end up in the oceans where they can persist at the surface for decades posing a multitude of threats to marine wildlife. Buoyant plastic debris is subjected to weathering and becomes porous (as chemical bonds within the plastics degrade) enabling it to both leach additives and absorb surrounding contaminants, presenting an increasingly dangerous ingestion risk to organisms.

A marine vertebrate that is known to ingest large amounts of plastic, presumably as a case of mistaken identity for food, is the Flesh-footed Shearwater (Ardenna carneipes) of Lord Howe Island, New South Wales, Australia. This island is home to the largest population of Flesh-footed Shearwaters, however the colony has been declining rapidly for over three decades. A. carneipes possess the highest plastic ingestion rates of all seabirds. This phenomenon is thought to be linked to increased morbidity within the colony, including a high heavy metal body burden of individuals, along with decreased body condition, reproductive rates and juvenile survival.

These birds forage within the Tasman Sea and the high amounts of plastics observed within the colony suggest that the Tasman is contaminated with plastic debris. This study was carried out in inshore and offshore areas of the south east Australian marine environment and aimed to categorize and quantify buoyant marine plastics. An additional aim of this study was to provide a toxicological assessment of the metals associated with: 1) sea-surface plastic fragments that A. carneipes were likely to ingest, and 2) different polymer types retrieved from both inshore and offshore areas.

Buoyant marine plastics were collected on a voyage that sailed from Hobart to Sydney in the autumn of 2013 and 2014. Synthetic particles were collected on the voyage via surface net tows and then later sorted, weighed and quantified in the laboratory. Additionally, Attenuated Total Reflectance Fourier Transform Infrared spectroscopy was used to determine the polymer type of individual particles and identify possible Flesh-footed Shearwater ingestion material from offshore samples. Elemental analysis via Neutron Activation Analysis revealed that all plastic fragments contained substantial amounts of heavy metals and metalloids of toxicological concern. Inshore plastics were more contaminated than offshore plastic fragments. However, the offshore A. carneipes ingestion material also contained substantial concentrations of heavy metals and metalloids, indicating that plastic ingestion could be providing the birds with chronic doses of toxicologically significant elements.