MAP Technical Reports Series No. 106 UNEP

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widespread, with secondary effects (hypoxia/anoxia in the bottom waters) being of but little
significance. Eutrophication causing conditions arise to a large extent from the effects of effluent
discharges from urban agglomerations and only in a few cases from inputs of rivers. If we
exclude a number of lagoon areas (Orbetello, for example) the negligible damages caused by
eutrophication occurring on Italy's western coasts is due, in large part, to the hydrodynamic and
morphological characteristics of these seas: the rapid processes of exchange with open sea
waters, the resulting dilution factors and the low water residence times all attenuate the
phenomena.
This is not the case throughout the northern Adriatic Sea. Apart from receiving huge
quantities of fertilizing substances, this part of the Adriatic is very shallow (only 50 meters on the
line from Rimini to Pula) and has physical and hydrodynamic characteristics which tend to
segregate the nearshore and offshore systems for long periods; this is particularly noticeable
in the area to the South of the Po delta, where, in the summer, water residence times may reach
40-50 days. Eutrophication under such conditions can be serious.
Italian West coast seas and Islands
Ligurian Sea. In general eutrophic conditions are not found in the Ligurian Sea. Near
Genoa, waters show low trophic levels with orthophosphate values between 0.02-0.31 mg-at/m 3 ,
nitrite-nitrogen levels between 0.5-41.8 mg-at/m 3 , and 1.2-4.1 mg/m 3 of chlorophyll-a (Genovese,
1979). Carli et al. (1992) also found similar conditions in two coastal stations close to Genoa
(Genoa Sturla and Genoa Quinto), and in the generally oligotrophic Bay of Riva Trigoso east of
Genoa (Carli et al. 1994). Variations over time in the phytoplankton populations off Chiavari
(eastern Liguria) also shows low autotrophic biomass (chlorophyll-a mean 0.2 mg/m 3 ; maximum
of 5.4 near the coast), (Cattaneo and Fabiano, 1982).
The generally oligotrophic characteristics of the Ligurian offshore waters are confirmed
by Innamorati et al. (1985; 1986a) who found phytoplankton concentrations rarely to exceed
200,000 ind/litre (200,329 cells/l with Cryptomonas spp. dominant in 1980 and 278,063 cells/l
with Amphidinium curvatum dominant in 1979). Similar conditions extend into the waters of the
Tuscan archipelago and of the northern Tuscan Tyrrhenian Sea; phytoplankton populations
normally show low concentrations (mean value in July 1983 11,400 cells/l.), (Innamorati et al.,
1986b, 1992; Lazzara et al., 1989).
Off the La Spezia Harbour, Zurlini (1991) conducted a study on the nutrient loads
adjoining the port area, and defined their trophic state on the basis of the criteria recommended
by the OECD (1982). Overall, from the various sources the roads of La Spezia receive 86.1
tons/year of phosphorus and 506.2 of nitrogen, giving the system mesotrophic characteristics
with a tendency towards eutrophy in the most internal areas directly affected by the urban inputs.
Cattini et al. (1992) reach the same conclusions, highlighting the fact that the highest values of
eutrophy are found near the port area of La Spezia, where a maximum chlorophyll-a value of
15.4 mg/m 3 was found.
The situation close to the mouth area of the River Arno is interesting. Although in
general high nutrient concentrations are found (annual averages of 9.5 mg-at/m 3 of nitric+nitrous
nitrogen and 1.02 of orthophosphate) in this area, phytoplankton biomass values are low (annual
average 180,000 cells/l and 4 mg/m 3 of chlorophyll-a). The apparent inability of algae to
assimilate the nutrients available seems to be due to inhibitory toxic substances (synthetic
detergents and surfactants) discharged from industrial plants located in the hydrographic basin
of the Arno (Innamorati et al., 1989).