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S. Caluo et al. /Science of the Total Environment 165 (1995~23-31 29

branch of the Atlantic current in the Sicilian
Channel.
Also, mean summer values of nutrient concen-
tration (Fig. 9), measured in 1992 in the Isola
delle Femmine station, showed a summer in-
crease more marked than off Sciacca (Fig. 10).
This is probably due to the higher summer popu-
lation density on Tyrrherian coast.
14 . . ,. . . , . . *. . . ,., , . . , , .
0 10 20 30 40 50
DEPTH Iml 4. Discussion
Fig. 8. Thermal profiles recorded at the Isola delle Femmine
station both during the summers of 1991 and 1992, and at the
Sciacca station during the summer of 1992. The results of observations carried out along
the Tyrrherian coast of Sicily show that amor-
phous mucus aggregates, manifesting similar
gates; with only a bloom of Ectocarpaceae showing characteristics to these in the Adriatic sea, were
thick gelatinous sheaths being observed (Fig. 7). widely present only during the summer of 1991.
As reported by Giaccone (pers. commun.), a This phenomenon did not re-occur in 1992.
massive growth of Ectocarpaceae occurred along On the contrary, in our opinion, the pheno-
the Jonian coast, although of a minor intensity mena of threadlike algae mucus aggregates re-
compared to 1991. ported along the Jonian coast and Sicilian Chan-
The analysis of thermal profiles (Fig. 8) nel during the summer of 1991, rather than those
recorded in the Isola delle Femmine station shows from Adriatic locations, should be compared to
significant temperature differences within the first those reported by Sartoni and Sonni (1992) for
15 m of depth between August 1991, character- the northern Tuscany coast. Moreover, in 1992,
ized by colder water, and August 1992. The low there was a decrease in the growth of filamentous
temperature values recorded offshore from Sci- algae compared to the previous year.
acca are related to the influence of the southern At the present time, only hypotheses are poss-

I I

0.08 ‘12
7
Chl a &g/l) PT P-PO4 N-NH4 N-NO2 N-NO3
Fig. 9. Mean chlorophyll a, total phosphorus and nutrient concentrations during the spring and summer of 1992 at the Isola delle
Femmine station.