FLOWERING OF ZOSTERA-MARINA IN THE LAGOON OF VENICE (NORTH ADRIATIC, ITALY)

The flowering of Zostera marina was studied in a shallow meadow in the Venice lagoon (North Adriatic Sea) in spring and summer 1995. Vegetat ive and fertile shoot density and size were recorded during the flower ing period. Spathe maturation was divided in six phases according to d ifferent stages of anthesis. New spathes were first observed in Februa ry and anther and pistil maturation proceeded until March. The beginni ng of anthesis, with styles erecting, occurred in April while fruits a ppeared in May and June. A statistically significant difference betwee n fertile and vegetative shoot height was found for all months. The st art of flowering (February-March) appears to be early in the Venice la goon in comparison to Atlantic European sites, where it starts from Ju ne onward. A six-month long flowering period is one of the longest obs erved. The estimated potential seed production seems limited if compar ed with the values relative to North European and North American coast s.