Marine Bacteria and Other Heterotrophs as Food for Zooplankton in the Strait of Georgia during the Winter

Abstract

Microbiological investigation was carried out in the waters of the Strait of Georgia during the winter to study the occurrence of heterotrophic microorganisms in relation to other particulate organic materials, including plankton and detritus. High microbial activity was measured in the euphotic zone, where marine bacteria and allied microorganisms were chiefly found on the particulate matter having diameter less than 25 μ. Their standing crop was estimated by different methods to be between 40 and 3000 mg C/m² and some of this was consumed by the zooplankton, which were found to have concentrated the bacteria by a factor of around 10⁵. Only the highest levels of microbial production were estimated to be sufficient for the growth of zooplankton and generally the bacterial activity was only sufficient to support a subsistence level of life for marine copepods in the Strait of Georgia.