The Loss of Diatoms in the Spring Bloom

The sinking of diatoms towards the end of the spring bloom contributes to the loss of organic material below the mixer layer. Earlier work is reviewed. The study of Peinert et al. (Neth. J. Sea Res. 16, 276 (1982)) in the Kieler Bucht was reworked assuming that the algal reproductive rate can be derived from the ratio of a radiocarbon measurement to stock in carbon. This method revealed a somewhat greater loss. The material of Marshall & Orr (J. mar. biol. Ass. U.K. 16, 853 (1930)) was reworked with an estimate of the diatom sinking rate. It was assumed that the difference between the algal reproductive rate and the grazing rate was constant in the shortest intervals of time and depth. A method was developed to estimate production, the quantity grazed and the quantity sunk. During the spring outburst, diatoms are lost, probably by detrainment, but at the end of the outburst there is a sudden loss. The quantity grazed may have been estimated somewhat more precisely.