Slicks associated with Trichodesmium Blooms in the Sargasso Sea

NATURAL slicks are apparently formed by the ripple-damping action of monomolecular layers of organic matter which have an effective strength of only a few dynes/cm or less and are visible against the adjacent rippled waters only in relatively calm, weather1–4. One of the few correlations of slick with source was made by Grøntved5 when an oily slick of several square miles in the North Sea was found to contain a high oily, senescent and dense patch of the diatom Coscinodiscus concinnus. The existence of blue-green algae of the genus Trichodesmium in the open ocean6, and its wide distribution7 and ability to discolour water as well as some of its ecology9,10 has long been recognized. The purpose of this communication is to describe blooms in which well-defined and surfactant slicks were associated with dense patches of Trichodesmium species.