Seasonal variation and yield of sulfated polysaccharides in seaweeds from the Venice Lagoon

Three red seaweeds from the Venice Lagoon: Gracilaria gracilis, Gracilaria vermiculophylla, Gracilariopsis longissima and the green seaweed Ulva rigida were investigated to determine the yields and the annual fluctuation of sulfated polysaccharides (SP) for biotechnological applications. The Gracilariaceae and U. rigida were investigated and evaluated taking into account various environmental parameters of the water column and surface sediments. The annual production of SP was the highest for G. longissima (13.2 tons dw ha-1 year-1), followed by G. vermiculophylla (11.4 tons dw ha-1 year-1) and G. gracilis (7.4 tons dw ha-1 year-1), whereas U. rigida showed the lowest production (2.7 tons dw ha-1 year-1). High nutrient availability, turbidity and phytoplankton blooms inhibited the production of SP in the red seaweeds especially in summer. The SP produced by Gracilariaceae in March and April, at water temperatures ranging between 13°C and 17°C, accounted for more than half of the total annual production. In contrast, U. rigida produced the highest quantity of SP (ulvan) in June with temperatures >25°C.