College of Marine and Environmental Sciences, James Cook University, Townsville QLD, Australia
mark.hamann@jcu.edu.au
Last month researchers reported that between 5 and 13 million tonnes of plastic enter the world’s oceans each year (Jambeck et al., 2015) and large quantities originate from countries in the Indian Ocean region. It is clear from this study and previous research that plastic pollution has become a ubiquitous problem affecting the world’s oceans and coasts. An example of the magnitude of the issue occurred in 2014 when popular media reported that frequent sightings of marine debris floating within the south-eastern Indian Ocean were hindering the search efforts for missing commercial airliner MH370 (Pattiaratchi & Reisser, 2014). Yet, despite the clear potential impact to coastal ecosystems, few data on the scale and magnitude of the problem exist from the Indian Ocean.
The pollution of the ocean is known to affect marine turtles (e.g. Wabnitz & Nichols, 2010), and in 2014 Schuyler and colleagues reported in Conservation Biology that the impact of plastic on marine turtles was increasing (Schuyler et al., 2014). Most of their data, however, came from studies in the Pacific and Atlantic Oceans, with numerous knowledge gaps remaining for sea turtles in the Indian Ocean. For example, we don’t yet know which turtle species are impacted, and we lack information on high-risk areas where marine plastics abound (Vegter et al., 2014). While data from seabird studies and oceanography offer some information, further insight into these gaps are required before we can fully assess the vulnerability of Indian Ocean turtles to plastic pollution.
Examples of marine plastic pollution affecting marine turtles in the Indian Ocean come from the Maldives and the Arafura Sea region of Australia. While documentation and removal of ghost nets has occurred in Australia since the late 1990s, it has only been in recent years that researchers have been able to quantify the risk to marine turtles (Wilcox et al., 2013; 2014). Ghost net impacts were first described as an issue for marine turtles in the Maldives in the late 2000s. In 2011, a project began to document the occurrence of ghost nets and entangled turtles, and ultimately used the data to try and mitigate the threat (Stelfox et al., 2014). Data collected in both the Maldives and the Arafura Sea region strongly indicate that ghost nets pose a significant risk to marine turtles. Exacerbating the problem, discarded nets often drift to these locations from overseas fisheries, requiring solutions that will take considerable international negotiation across multiple jurisdictions.
The high volume of plastic debris and discarded fishing gear within the Indian Ocean is almost certain to pose an ongoing risk to marine turtles. Only time will tell whether species or population scale impacts may occur. There is certainly scope for increased monitoring and research focus to improve our knowledge and quantify the 2014 baselines. In terms of management, improved mitigation of plastic pollution will require a reduction of plastic inputs into coastal and marine systems. At the very least, this will require targeted efforts towards changing the behavior of people, reforming policy and boosting infrastructure to process waste. Marine turtles are often used as flagship species for environmental change, and marine turtle-based tourism could be a key component of future strategies to minimize the vulnerability of marine turtles to plastic pollution.
Jambeck, J. R., R. Geyer, C. Wilcox, T. R. Siegler, M. Perryman, A. Andrady, K. L. Law, et al.2015. Plastic waste inputs from land into the ocean. Science 347: 768-771.
Pattiaratchi, C. & J. Reisser. 2014. The difficulty of searching for MH370 in a giant rubbish patch. The Conversation http://theconversation.com/the-difficulty-of-searching-formh370-in-a-giant-rubbish-patch-25083
Schuyler, Q., B. D. Hardesty, C. Wilcox & K. Townsend. 2014. Global analysis of anthropogenic debris ingestion by sea turtles. Conservation Biology 28: 129-139.
Vegter, A. C., M. Barletta, C. Beck, J. Borrero, H. Burton, M.L. Campbell & M. Hamann. 2014. Global research priorities to mitigate plastic pollution impacts on marine wildlife. Endangered Species Research 25: 225-247.
Wabnitz, C. & W. J. Nichols. 2010. Plastic pollution: An ocean emergency. Marine Turtle Newsletter 129: 1-4.
Wilcox, C., B. D. Hardesty, R. Sharples, D. A. Griffin, T. J.
Lawson & R. Gunn. 2013. Ghost net impacts on globally threatened turtles, a spatial risk analysis for northern Australia. Conservation Letters 6: 247-254.
Wilcox, C., G. Heathcote, J. Goldberg, R. Gunn, D. Peel & B. D. Hardesty. 2014. Understanding the sources and effects of abandoned, lost, and discarded fishing gear on marine turtles in northern Australia. Conservation Biology 29: 198-206.
OTHER USEFUL RESOURCES