A bright blue phytoplankton bloom, separated into two close yet separate areas, can be observed in the North Sea off the coast of the United Kingdom. Also visible by the coast are sediments from several rivers. Southwest of the phytoplankton bloom are sediments from the rivers Witham, Welland, Nene and Great Ouse, in the Wash, the square-mouthed bay and estuary on the northwest margin of East Anglia on the east coast of England, where Norfolk meets Lincolnshire. It is among the largest estuaries in the United Kingdom. Further down the coast are sediments from the River Thames, east of London. On the opposite side of the island are sediments from the River Severn in the Severn Estuary and the Bristol Channel.