MICROALGAL COMMUNITIES ON PROTECTED STEEL SUBSTRATA IN SEAWATER

The development of microalgal communities on steel substrata protected from corrosion is described. Four non-toxic substrata were used, cathodically protected steel, painted steel, cathodically protected painted steel, and a perspex control. Substrata were exposed at Cullercoats on the north-east coast and at Cowes on the south coast of England. Significant differences in the number of microalgae on the substrata were found after 25 days exposure at Cullercoats. No significant differences in the number of microalgae were found after 50 days at Cullercoats, and few for 28 or 56 days at Cowes. No significant differences were found in community composition between the substrata, but communities had changed significantly between the 28 and 56 days exposures at Cowes. Some substratum preference is shown by individual diatom species, and this is discussed in respect to the physical and chemical nature of the substrata.