Observations on a bloom of the neuston alga,Nautococcus pyriformis, from southern England with an explanation of the floatation mechanism

Abstract

Conditions prevailing during a Nautococcus bloom in southern England are described. At the height of the bloom, 3·75–7·5 × 105 cells cm-2 water surface were recorded. High temperature, high pH and stagnant, eutrophic water may be necessary for the growth of the species. The floatation mechanism relies upon the presence of a hydrophobic surface layer. An angle of contact of nearly 90° was calculated from theory for a Nautococcus cell semi-immersed at the air-water interface, in agreement with observation. The cell surface is covered with an irregular, pigmented extracellular layer. Histochemical results, combined with light microscopy suggest the material is hydrophobic and probably composed of a mixture of carboxylated polysaccharides and waxes.