 Thin layers occur in a wide variety of ocean environments, including estuaries, coastal shelves, fjords, bays, and the open ocean, and they are often associated with some form of vertical structure in the water column, such as pycnoclines, and in zones of reduced flow.Thin layers persist from hours to weeks while other small-scale patches of plankton exist for minutes.The presence of nutrients as well as coastal fronts, eddies, and upwelling zones greatly increase the persistence of thin layers.