Marine debris

The Southern Ocean is the most remote body of water in the world and we would expect it to be the least effected by litter from the populated regions. However, floating debris and plastics are found even here and as humans expand their numbers and their activities in the Southern Ocean we can expect that there will be more and more debris left behind. Plastic is generally less dense than water and so it floats and therefore concentrates on the sea surface where it is more visible to us and to other animals. This characteristic unfortunately leads to some of it being swallowed mistakenly for food. Some birds and fish commonly do this; and the results are never beneficial. 

Marine debris often washes ashore on west facing beaches of subantarctic islands, such as West Beach on Heard Island Photo: Paul Goldsworthy

 

This research documents the changes in plastics type, abundance and origins (usually by examination of markings) on selected beaches at Macquarie and Heard islands. These beaches are west facing and "capture" much material floating on the sea surface. Changes over time will indicate whether the plastics burden on the ocean is increasing. Direct collections of plastic at sea by surface (or neuston) nets are also made and are used to quantify the amount of plastics by expressing it on a "per hectare" basis.The research also investigates the particular plastics swallowed by some seabirds and seals. These pieces are analysed by infra-red spectrophotometry to define their composition and are assessed for their state of decomposition. The origins of these small pieces are being investigated. We encounter these pieces in seal faeces and in stomach samples from birds. A priority for future research is to determine whether plastics in the Southern Ocean are at levels that are causing harmful impacts on the wildlife.

Marine debris is collected from selected beaches to provide an indication of the diversity and source of rubbish in the Southern Ocean Photo: Paul Goldsworthy