Phaeocystis colony mucus components and the importance of calcium ions for colony stability

Abstract

The composition and properties of Phaeocystis colony mucus are st~ll largely obscure. In this study some components of the mucus were i d e n t ~f ~e d using a specific staining technique and the role of Ca2* and other cations as binding agent was investigated. In addition, the effect of Ca2' concentration on colony formation in batch cultures was studied. Colonies of Phaeocystis sp. were stained with alcian blue at 2 different pH values. This revealed that the colony mucus contained both carboxylated and sulfated polymers. Incubation of colonies in medium lacking one or more cations showed that calcium and magnesium ions were essential for the gelling of colony mucus, while potasslum ions had no influence. The percentage colony cells formed by Phaeocystis in batch cultures was reduced in medium with calcium concentrations below 2.5 mm01 I-'. No colonies were formed in medium with calcium concentrations below 1.5 mm01 1.' Growth rate was not dependent on calcium concentration. It is suggested that under natural conditions Phaeocystis colony firmness and morphology might depend on the composition of mucus polymers.