IMIS

Niskin bottle samples at 3m depth. At Santa Croce, SI, SE stations, samples were collected at 3m and 10m depth. Bi-monthly sampling from May 2008 to January 2009 in 6 sites close to mussel farms. Three sites were located outside the mussel farms and three inside. Samples were fixed with Ca(HCO3)2-buffered formaldehyde (0.8% final concentration) and cell abundance and species composition of phytoplankton were estimated according to Utermöhl’s method (1958), using an inverted microscope equipped with phase contrast, at 200-320-400x final magnifications. Variable volumes of seawater (25 and 50 ml, depending on cell concentrations) were settled for at least 48 h. Biomass is derived from cellular Carbon content and cell biovolume. Biovolume was calculated according to Edler (1979) and Hillebrand et al. (1999). Cell volumes were converted to carbon content using the formula introduced by Menden-Deuer and Lessard (2000).