BIODIVERSITÀ MACROALGALE E GRADIENTI ECOLOGICI DEGLI AFFIORAMENTI ROCCIOSI DEL LITORALE VENETO

Ecological gradients and macroalgal biodiversity in rocky outcrops along Venetian coasts. Fifty-five macroalgal species (42 Rhodophyta, 6 Chlorophyta and 7 Ochrophyta) were identified on 12 rocky outcrops, located at different distances from the coast (between 1 and 28 km) and depths (between 10 and 27 m), with different shapes (scattered, compact or flat rocks), height (0.4-4 m) and dimension (30-9,620 m2). Rhodophyta show the heights number of species (average outcrops 90%) and percent coverage (average outcrops 32%, out of a total of 37%). The macroalgal assemblages are dominated by sciaphilous species, also on the outcrops closer to the coast at shallower depths. The outcrops less affected by the Venice lagoon and rivers influence are characterized by taxa with partly or completely calcareous thalli (Peyssonnelia, Lithothamnion and Lithophyllum). In particular, on the outcrops located far from the coast, where the marine water dynamics prevail over the coastal ones, the coverage of bioconstructing algae increases.