Page 3 - Buia&al2001

Morpho-chronology of Posidonia oceanica seedlings 60/

Caruso). Along the coast near Taranto (Lama, Ionian Sea) seedlings were observed
ashore in June 1999. At each sites a number varying from 5 to 20 seedlings were
measured for the main morphological features. A group of juvenile shoots were sam-
pled at Favignana in 1995 (about 40 shoots), and were about 1-year-old (Gambi and
Guidetti, 1998). A second group of young plants was collected at Ustica, deriving from
seedlings observed in 1997, and sampled in 1998 (about 1-year-old, 5 shoots) and 1999
(about 2-years-old, 20 shoots). 27 shoots at Favignana (different from those reported
in Gambi and Guidetti, 1998) and 20 at Ustica (only shoots collected in 1999) were
measured for phenology; 17 shoots at Favignana and 16 at Ustica were suitable also
for the lepidochronological analysis. The scales of each shoot were carefully detached
from the rhizome according to their insertion rank; scale thickness was measured by an
electronic calliper in the centrai portion of the scale at about lO mm from its attachment
point (Pergent et al., 1989). Statistica! differences between seedlings of different areas
and between juveniles shoots were tested by one-way ANOVA.

Results and d.iscussion

The phenological features of the collected seedlings are shown in Tab. l, while
morpho-chronological characteristics of juvenile shoots are reported in Tab. 2.

Seedlings at Ustica derived from a ftowering observed in winter in the deep stands
off the island (Buia et al., 1999). Seedlings were settled from 0.5 to 15 m depth on
hard bottom covered by photophilous algae at Punta dell'Arpa and Punta Gavazzi,
while were settled among small stones and pebbles at Cala Parrino. At Ischia (Punta
Caruso), seedlings were settled from 2 to about 10m depth on hard substrata. A year
later, in May 1999, severa! seedlings have been recorded on a beach, near the Castello
Aragonese (Buia, pers. observ.). It can be hypothesized that these seedling events,
never recorded before at Ischia, could be somehow related to the temperature increase
observed in these last years also in the Gulf of Naples (Mazzocchi and Ribera d' Alcalà,
1995).

Tab. l - Mean values (st. dev.) of phenological variables of the analyzed Posidonia oceanica see-
dlings.

Medie (e d s.) delle variabili fenologiche dei gemwgli di Posidonia oceanica studiati.

Locations Ustica 1997 Ustica 1997 Ustica 1997 Ischia 1998 Taranto 1999
Punta Arpa Cala Parrino Punta Gavazzi Punta Caruso Lama
Depth range (m) ashore
No. of seedlings e1Camined 2-15 2-5 2-5 2-10 15
Period of observation 20 8 5 20 Junc
Presumed age (months) September September September June >l
leaflength (cm) 3 3 3 l 1.3 (0.7)
length oflongest leaf(cm) 5.3 (2.3) 6.0 (2.9) 5.0 (2.2) 2.6 (1.7)
leafwidth (cm) 7.6(1.1) 9.1 (2.0) 7.0 (1.1) 4.5 (0.9) 2.5 (0.3)
no. lealìshoot 0.59 (0.07) 0.55 (0.07) 0.53 (0.06) 0.3 (0.1) 0.28 (0.03)
leaves with eroded ape" (%) 7.8 (1.2) 6.6(1.1) 7.8 (0.7) 7.2 ( 1.5)
leaves with brown tissue (%) 14 13.2 2.5 7.6 (0.9)
scale number per shoot 5 15 15.3 2.5 (0.6)
no. leaves/shoot afìer gerrnination 6.2 (1.0) 4.8 (0.92) 6.0 (0.9) 1.8 (0.2) 1.0 (0.8)
secondary root number 14.2 (2.0) 11.5 (0.70) 13.8 (1.6) 1.6 (l. l)
seed length (cm) 4.6 (1.4) 3.7 (0.6) 4.4 (0.8)
1.8 (0.2) 1.7 (0.2) 1.7 (0.5)