Particulates of the surface microlayer of open water in the central Arctic Ocean in summer

The particulate content of samples of the surface microlayer water collected from the open water between ice floes at latitudes 88° to 89°N in August 2001 was examined by transmission electron microscopy. Concentrations varied from 2×107 ml−1 to more than 1014 ml−1 although bacterial counts made in the same samples varied by only about 50%. Size distributions of the particles were also very variable with modal diameter sizes of 10 nm in some samples and 50 nm in others, the 50-nm particles appearing to be clusters of the 10 nm ones. A mucus-like material held the particles together in rafts, strings or in balls. The largest particles were compact electron-opaque aggregates of smaller particles. The particles appeared to have very similar characteristics to the “microcolloids” observed in bulk seawater in lower latitude oceans. X-ray analyses of the elements with atomic numbers >16 showed all signals to be weak, suggesting a mainly organic composition. The elements that were most commonly greater than background levels were all those associated with marine biological activity. Rapid aggregation of polymers to form colloids has been noted and is likely to be an important cause of the observed variability of particulate concentrations in the surface microlayer. The possibility of an equally rapid dispersal under the influence of ultraviolet light is raised.