MAP Technical Reports Series No. 106 UNEP

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Southern shores. A corresponding case is reported for the Gulf of Gela. Increased
trophic conditions induced by urban and industrial waste had detrimental effects on the fishing
industry. Modification in the texture of the sediments, which had become sandy-muddy, favoured
limivorous species of little commercial interest; thus, high productivity is actually contrasted by
a low value of the fish caught (Arculeo et al., 1990).
Eastern shores. Giacobbe and Maimone (1991) report widespread presence of
significant amounts of Dinophysis spp. in the coastal waters off Syracuse with concentrations
reaching 2,000 cells/l. De Domenico (1979) reports eutrophic conditions off Augusta, where
recurrent blooms occur above all in the western section. In January 1977 very high nutrient
concentrations were measured in the north-western and central part of the roads, with 1.6 mgat/m
3 of orthophosphate and 20.0 mg-at/m 3 of nitric nitrogen.
Ionian Sea. In the Gulf of Taranto, microalgae blooms occur during the summer months
only in the bay known as the "Mare Piccolo". One report of this is given by Magazzu' (1982) who
describes a bloom which occurred in 1973.
Southern and Central Adriatic Sea
Puglia, Gargano, Abruzzi, Marche. Conditions of oligotrophy normally predominate
along the easter coasts of Puglia. Marano and Rizzi (1985) report fairly high concentrations of
phytoplankton organisms only for the areas corresponding to Porto Nuovo, Bari, and the Gulf of
Manfredonia.
The coastal Lake of Varano (Foggia) is more seriously affected by high trophic levels;
this lagoon is periodically subject to eutrophic events with fairly serious dystrophic
consequences. There is a risk of widespread putrefaction during the summer months unless
increased exchange with sea-water is guaranteed (De Angelis, 1964). In a study carried out from
May 1985 to April 1986, Tolomio et al. (1990) highlight the presence of high concentrations of
nutrients and autotrophic biomass.
There are few reports from the southern and central Adriatic about events of
eutrophication; in fact, this area is generally considered oligotrophic. South of the Conero
promontory (Ancona) waters three miles off shore are between mesotrophy and oligotrophy;
small areas of eutrophy only occur along the coast near the mouths of rivers and urban
agglomerations (Artegiani et al., 1979).
Going north reports about increased trophic levels and microalgae blooms become
more numerous. Off the Conero promontory, Artegiani et al. (1985) record a large-scale bloom
of Gymnodinium sp. monitored during October 1984. This bloom, indeed the largest in
distribution and intensity during the last twenty years, started at the end of July 1984, and actually
affected a large part of the north-western Adriatic. Very high biomass values were found adjacent
to the river Po delta, and in the zones close to larger towns; close to the Po delta chlorophyll-a
values in excess of 600 mg/m 3 were measured (Emilia-Romagna Region, 1985; cf. Fig. 11).
Although its intensity and distribution waxed and waned, the bloom died out in December of the
same year. Blooms caused by this microalga have special features which differ from those of
other dinoflagellates, since this organism is able to withstand steep thermal and salt gradients
without showing signs of stress. The start of the bloom (July) coincided with water temperatures
around 24EC, while by December when the bloom disappeared, the temperature had dropped
to 8-9EC. Unaffected by salinity it was equally abundant both in low-salinity (20-24 in the area
near the Po delta) and high-salinity areas (35-37 off Ancona). None of these episodes caused
anoxia of the bottom waters, probably