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210 L. TRANCHINA et al.

TABLE VI Trace-metal concentrations (mg g21 dry weight) in Posidonia oceanica rhizomes
(values are means over three samples from different transects and collected at the same depth).

Cd (1.0– 8.6)Ã Cu (5.7– 20.2)† Pb (0.7– 10)Ã Zn (105– 180)Ã

Egadi 2.8 + 0.5 13 + 1 14 + 1 220 + 30
Station 1 2.7 + 0.5 9+1 14 + 2 190 + 40
Station 2 3.1 + 0.5 7+1 8.8 + 0.7 210 + 30
Station 3
Trapani 2.3 + 0.4 11 + 2 11 + 1 170 + 30
Station 1 2.4 + 0.4 8+1 7.4 + 0.6 180 + 20
Station 2 3.1 + 0.6 8+1 13 + 1 280 + 30
Station 3
Marsala 2.7 + 0.4 5+1 9+1 700 + 100
Station 1 3.1 + 0.5 6.2 + 0.6 7.5 + 0.7 310 + 50
Station 2 1.9 + 0.3 2.5 + 0.6 8.7 + 0.8 290 + 30
Station 3
Carini 4.0 + 0.6 10 + 1 9.8 + 0.8 180 + 20
Station 1 3.7 + 0.6 10 + 2 10 + 1 180 + 30
Station 2 3.3 + 0.6 12 + 2 12 + 1 180 + 30
Station 3

Note: Samples from different transects collected at the same depth have been analysed as a whole.

ÃSanchiz et al., 2000.
†Campanella et al., 2001.

and is present in smaller amounts in scales. The levels of Pb were always higher in scales
than in rhizomes, their differences being statistically significant and proved by F-test
(P-value 0.0001). The mean concentration of Pb in leaves shows values close to those
measured in scales (P-value from the F-test 0.0733). Zinc is present in high concentrations
in all tissues of P. oceanica and less concentrated in rhizomes than in scales and leaves (LSD
test). Levels of Zn found in the leaves from Station 1 of the Marsala site (700 + 100 mg g21
dry weight) were found to be a few times higher than in leaves from other stations. These
values are comparable with those found by Sanchiz et al. (2000) in El Portu´s (Spain).

Statistical analysis, with a mean comparison and LSD test for concentrations of trace
metals in the same portion of the plant from different sites, has shown that the most signifi-
cant differences are the highest values for Pb in Carini site and the highest values for Zn in
Marsala site. This applies to both rhizomes and scales. Comparison of values within the same
site has shown that values in different stations (i.e. different depths) are fairly homogeneous,
the Zn concentration from Station 1 in Marsala site being the only noticeable difference.

Some authors have found a positive correlation between levels of some metals in sediment
and in P. oceanica (see Maserti et al., 1988, for mercury). This correlation was not found for
other elements, such as aluminum (Malea, 1993). Table VII shows the correlation matrix for
trace metals in sediments and tissues. No element shows a significant correlation between its
concentration in sediments and its concentration in tissues, in agreement with Sanchiz et al.
(2000). Cu concentrations in different portions of the plant show a positive and significant
correlation. The same applies for Zn. Cu and Zn are always negatively correlated. Cu and
Pb in scales are positively correlated.

The mean levels of metals of our survey are generally low and in agreement with literature
data (Warnau et al., 1995; Sanchiz et al., 2000; Baroli et al., 2001; Campanella et al., 2001)
in uncontaminated areas of the Mediterranean Sea.

Tables VIII –X show the radionuclide specific activities measured in sediments and in
P. oceanica rhizomes and scales. Data are shown if the value is larger than the critical
limit (Currie, 1968). The lowest detection limits (LDL), calculated according to Currie
(1968), for sediments (for a 200 g sample and a measurement time of 2.5 Â 105 s), have