Bioresource Technology, Vol.50, No.2, 165-173, 1994
GRACILARIA DISTRIBUTION, PRODUCTION AND COMPOSITION IN THE LAGOON OF VENICE
Until the end of the 1980s, Gracilaria, in terms of biomass production, was the second macroalgal genus populating the lagoon of Venice. The dominant species, Gracilaria verrucosa (Huds.) Papenf., before the massive harvesting for agar extraction began in the mid-1980s, accounted for a mean standing crop and an annual production of 36000 and 132000 t (wet wt), respectively. Nowadays, dense populations of this species are missing and both standing crop and production are markedly reduced. On the basis of Gracilaria samplings conducted at three stations representing the main biogeochemical differences of the lagoon, it appears that this species, in the eutrophicated areas, has the capacity of accumulating nitrogen and phosphorus more efficiently than any other macroalga, probably because of its higher organic content In contrast, the carbohydrate content was higher in the unpolluted areas because of the younger age of the sampled specimens. Considering the C:N:P atomic ratios in thalli, the phosphorus availability can be suggested as a possible limiting factor for Gracilaria growth in oxic and unpolluted areas. No significant chlorinated hydrocarbon accumulation was found in the samples from the different areas. In contrast, heavy metals, particularly Mn, Zn, Pb, Cu, Fe and Ni, were efficiently accumulated by this species in the polluted areas, but only the Mn concentration was appreciably higher than in the other algal species.