Characteristics of flotsam samples from Sargasso Sea

Clumps of pelagic Sargassum as well as floating marine debris were collected during cruise MSM41 of the German research vessel Maria S. Merian in the Sargasso Sea (subtropical NW Atlantic) in April 2015. Samples were taken with a dip net (mesh size: 1 mm) from the rescue boat of the research vessel at 19 stations distributed in coordination with the other sampling activities of the cruise. Few, mostly larger, debris samples were taken from aboard the research vessel using a dip net with a mesh size of 9 cm. The exact sampling position of each floating item was recorded by a handheld GPS. In total, 42 Sargassum samples and 41 samples of marine debris were collected. On board the vessel, the Sargassum samples were analyzed for their species composition (Sargassum natans, Sargassum fluitans, indeterminable small fragments). Each fraction was weighed (wet weight) after the algae had been blotted on tissue paper to remove adherent seawater. The type of each debris sample was determined and the sizes of the debris samples were measured. Small objects were preserved in buffered seawater-formalin solution for later analysis of the associated biota. Small sub-samples have been taken from samples, which were too large to be preserved in total. Polymer compositions of the plastic debris samples were analyzed by Near Infrared Spectroscopy.