MAP Technical Reports Series No. 106 UNEP

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Tyrrhenian Sea. One area repeatedly affected by high trophic conditions and significant
dystrophic processes is the Lagoon of Orbetello (Grosseto - southern Tuscany). The large
amounts of nutrients of urban origin which have been discharged into the lagoon for 15 years
promote periodic algae blooms which, particularly during the summer and autumn, cause
frequent crisis of anoxic. Still, once normal conditions have been restored the ecosystem
generally recovers rapidly (Lenzi and Salvatori, 1986). The resulting damage to the fish
population of this lagoon ecosystem have led to short-term measures including the collection
of the macroalgal biomass and the forced exchange of waters (Lenzi, 1992).
Dystrophies caused by eutrophication phenomena are not reported in the coastal
discharge area of the River Tiber (Pettine et al., 1983). In spite of the high trophic levels normally
found at the two mouths of the river, as a result of the very active hydrodynamics of the site, the
natural conditions of oligotrophy of the Tyrrhenian Sea and/or the presence of toxic substances
capable of inhibiting the growth of autotrophic biomass, no microalgal blooms are reported
(Zoppini et al., 1989).
After the conspicuous increase in the human population of the adjacent areas, which
started in the '30s, the coastal Lake of Sabaudia (7 km 2 in area, in southern Latium) gradually
passed into a state of eutrophy; sewage inputs from the town of Sabaudia (5,000 residents +
15,000 tourists during the summer season) and from a pig farm of 1,500 head led to recurrent
anoxic crises. The most serious one occurred in July 1979, when all the fish stocks were
destroyed (Perdicaro et al., 1980). From 1980 the treatment of the sewage and the closure of
the pig-farm led to a gradual improvement of the basin (Perdicaro, 1985).
Other reports of eutrophic environments come from the Lagoons of Miseno, Fusaro and
Patria (Naples), where the discharge of untreated sewage and industrial effluents have seriously
reduced water quality. For the Fusaro lagoon, Carrada et al. (1988) also reports a bloom of
Gymnodinium catenatum (dinoflagellate capable of synthesizing PSP group toxins) with
concentrations of 6,000,000 cells/l.
Gulf of Naples. Two subsystems can be recognized in the Gulf of Naples: one is of
"open sea water" with oligotrophic characteristics essentially determined by waters originating
offshore; the other, nearshore system presents pronounced eutrophication phenomena triggered
by the inputs along the coast (Genovese, 1979). However, there are significant variations in the
coastal area; because of the poor circulation of the waters particularly in the
summer months, plumes of dark waters caused by sewage outfalls may often be identified.
Carrada et al. (1979) recorded high algal biomass values to the East of Naples in the areas with
the highest nutrient input during the summer of 1977. Zingone et al. (1985) report a bloom
caused by Chaetoceros simplex in the summer of 1983 that reached 120,000,000 cells/l in the
areas most affected by the effluents from the city of Naples. Ribera D'Alcalà et al. (1989)
encountered algal blooms in the same area in May 1987 which, although not widespread,
reached peak concentrations of chlorophyll-a of 176 mg/m 3 . Modigh et al. (1985) emphasize the
inverse correlation between salinity and chlorophyll-a values that further underlines the role of
nutrient-rich waters and biostimulants from the sewage system.
Carrada et al. (1982) found in the Gulf of Salerno in November 1981 the coast-offshore
gradients of the autotrophic biomass to be low with concentration between 0.1 - 0.8 mg/m 3 of
chlorophyll-a.
No further episodes of eutrophication are reported from other areas of the Tyrrhenian,
including southern Campania and the Calabrian coast which seems to be unaffected by
eutrophication (De Domenico, 1979).