11 Feb 2021

11 Feb 2021

Review status: this preprint is currently under review for the journal OS.

Plastics in the Indian Ocean – sources, fate, distribution and impacts

Charitha Pattiaratchi1, Mirjam van der Mheen1, Cathleen Schlundt2, Bhavani E. Narayanaswamy3, Appalanaidu Sura4, Sara Hajbane1, Rachel White5, Nimit Kumar6, Michelle Fernandes7, and Sarath Wijeratne1 Charitha Pattiaratchi et al.
  • 1Oceans Graduate School and the UWA Oceans Institute, the University of Western Australia, Perth, 6009, Australia
  • 2GEOMAR, Helmholtz Centre for Ocean Research, Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • 3Scottish Association for Marine Science, Oban, Argyll, PA37 1QA, Scotland, UK
  • 4National Centre for Coastal Research, Ministry of Earth Sciences, Chennai, 600100, India
  • 5School ofBiological Sciences, the University of Western Australia, Perth, 6009, Australia
  • 6Ministry of Earth Sciences (MoES), Indian National Centre for Ocean Information Services (INCOIS), Hyderabad-500090, India
  • 7National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Goa, India

Abstract. Plastic debris are the most common and exponentially increasing human pollutant in the world's oceans. The distribution and impact of plastics in the Pacific and Atlantic Oceans have been the subject of many studies but not so for the Indian Ocean (IO). Some of the IO rim countries have the highest population densities in the world and mis-management of plastic waste is of concern in many of these IO rim states. Some of the highest plastic-polluted rivers end up in the IO with all this suggesting that the IO receives a tremendous amount of plastic debris each year. However, the concentration, distribution and impacts of plastics in the IO are poorly understood as the region is under-sampled compared to other oceans. In this review, we discuss sources and sinks, which are specific for the IO as well as unique atmospheric, oceanographic and topographic features of the IO such as reversing wind directions due to the monsoon, fronts and upwelling regions that control plastic distribution. We identified hotspots of possible plastic accumulation in the IO, which were different in the two hemispheres. In the northern Indian Ocean, the majority of the plastic material will most likely end up being beached due to the absence of a sub-tropical gyre, whereas in the southern Indian Ocean, the garbage patch is not well defined and there may be leakage of plastics into the southern Atlantic Ocean. Hotspots of predicted plastic accumulations are identified here as well as the vast knowledge gaps about the plastic issue of the IO and point to the most striking future investigation topics.

Charitha Pattiaratchi et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on os-2020-127', Anonymous Referee #1, 01 Apr 2021
  • RC2: 'Comment on os-2020-127', Anonymous Referee #2, 06 Apr 2021
  • RC3: 'Comment on os-2020-127', Anonymous Referee #3, 14 Apr 2021

Charitha Pattiaratchi et al.

Charitha Pattiaratchi et al.


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Short summary
The Indian ocean receives a large proportion of plastics but very few studies have addressed the sources, transport pathways and sinks. There is a scarcity of observational data for the Indian ocean. Majority of the plastic sources are derived from rivers although the amount derived from fishing activity (ghost nets, discarded ropes) are unknown. The unique topographic features of the Indian ocean that create the monsoons and reversing currents have a large influence in the transport and sinks.