Influence of nutrient factors on production of mucilage by Amphora coffeaeformis var. perpusilla

Widely distributed productions of mucilages affected the coasts of the Adriatic sea in the summers of 1988, 1989 and 1991 (the so-called “dirty sea” phenomenon). Samples taken in this area revealed a mix of diatom and dinoflagellate algae trapped in the mucilagenous matrix, but cultured isolates from the samples showed the species Amphora coffeaeformis var. perpusilla producing a kind of exopolysaccharide (EPS) very similar in structure to that of the floating pillows which appear in the Adriatic waters. The effects of growing concentrations of primary nutrients on EPS production by A. coffeaeformis were evaluated and the results showed a prevailing influence of nitrogen, alone or in synergy with phosphorus, with respect to phosphorus alone. EPS production never stopped, even during the stationary phase and never overlapped with growth curves. © 1997 Elsevier Science Ltd