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Abstract
Attachment, growth and carbohydrate metabolism of Amphora coffeaeformis cells on cathodically polarised and non‐polarised 304 stainless steel were evaluated when cells were grown under continuous illumination at 18°C for 8 d in medium prepared in synthetic seawater. Attachment to cathodically polarised steel was very poor as evident from lower values of cell dry weight, organic carbon chlorophyll a and protein. Levels of these decreased with time indicating the absence of algal growth on the stainless steel under these conditions. In contrast, on non‐polarised steel, the attachment of A. coffeaeformis cells was higher by a factor of 10 to 100. The observed non‐linear increase in algal cell dry weight, organic carbon, chl a and protein with time indicate active growth of the algal cells on non‐polarised steel. Although carbohydrate and protein were the most abundant constituents on both types of steel, there were apparent differences in their relative distribution. Carbohydrate was the most abundant organic constituent in the cells from non‐polarised steel, whereas protein was the major organic component in the algal cells from cathodically polarised steel. Such differences were also evident in proteimcarbohydrate, protein:acid soluble carbohydrate, carbohydratexhl a and proteinxhl a ratios in the cells from cathodically polarised and non‐polarised steel. Carbohydrate composition data indicate 10 to 100 times enrichment of acid soluble carbohydrates in the cells from non‐polarised steel. The observed increase in acid soluble carbohydrate was due to increased synthesis of this fraction in cells from non‐polarised steel. Under cathodic polarisation no such increase was observed. The consistent decrease in the acid soluble carbohydrate and increase in the protein:acid soluble carbohydrate ratio in cells from cathodically polarised steel suggest preferential loss of acid soluble carbohydrate. It is possible that this may play an important role in enhancing the effectiveness of cathodic protection in the control of fouling and/or corrosion of metals immersed in the marine environment.