The Plankton in the Upper Reaches of the Bristol Channel

The plankton collected at a station in the Bristol Channel in 1936-7 is related to chemical and hydrographical factors. On account of the varying speeds of the tidal streams, the observations refer, not to a single point, but to a series of points along a length of the channel. Gradients of salinity, phosphate, and a possible complicated gradient of oxygen saturation, were determined, and, from the average monthly salinities, an annual cyclical movement of water deduced.