A simple technique for counting marine debris at sea reveals steep litter gradients between the Straits of Malacca and the Bay of Bengal

A size and distance-based technique was used to assess the distribution, abundance and composition of floating marine debris in the northeast Indian Ocean. Densities of floating litter (>1 cm) were greater and more variable in the Straits of Malacca (578 +/- 219 items km(-2)) than in oceanic waters of the Bay of Bengal (8.8 +/- 1.4 items km(-2)). The density of debris in the Straits was correlated with terrestrial vegetation, and peaked close to urban centres, indicating the predominance of land-based sources. In the Bay of Bengal, debris density increased north of 17 degrees N mainly due to small fragments probably carried in run-off from the Ganges Delta. The low densities in the Bay of Bengal relative to model predictions may result from biofouling-induced sinking and wind-driven export of debris items. Standardised data collection protocols are needed for counts of floating debris, particularly as regards the size classes used, to facilitate comparisons among studies. (C) 2013 Elsevier Ltd. All rights reserved.