Plankton Production and its Control

Abstract

Vertical hauls between surface and 45 metres depth were made with a measuring net, throughout 1934, at a position 5 miles S.W. of Plymouth Breakwater incirca50 metres depth of water.The phytoplankton organisms were counted and also assessed from their content of plant pigments.A close relation was found between numbers of diatoms and their pigment contents after making allowance for the small size of three species.The phosphorus content of the phytoplankton was estimated on several occasions.The zooplankton organisms per cubic metre of sea were counted and estimations were made of their phosphorus content.The diatom population differed from that found in 1933, in which year the spring outburst was shorter but more intense, the sporadic summer outbursts were more intense, the autumn one lasted longer; and more phosphate was utilised by the plants during the first half of the year.