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The animal communities associated with H. stipulacea were studied by Cancemi et al. [29] and
Acunto et al. [105]. The former study, dealing with vagile fauna, was carried out in a meadow
occurring in Giardini Naxos harbour (Messina). Mollusca, Amphipoda and Decapoda with 18, 21
and 14 species, respectively, were the most abundant groups. The latter study, dealing with groups
of macrozoobenthos, was carried out in the meadow near the harbour of the island of Vulcano,
where Polychaeta, Crustacea and Mollusca with 23, 15 and 6 families, respectively, were the most
abundant.

The first studies on epiphytic algal communities on P. oceanica leaves were those carried out
on two P. oceanica meadows off Capo Passero (Syracuse): one near the island of Correnti, the
other near the island of Capo Passero. The studies were conducted in spring [13] and autumn
[106]. A total of 54 taxa at specific and infraspecific levels (later named species) (18 Rhodophyta,
8 Ochrophyta and 1 Chlorophyta) were found in the island of Correnti meadow, while 90 species
(51 Rhodophyta, 17 Ochrophyta and 4 Chlorophyta) were found in the island of Capo Passero
meadow. Because the largest number of species are found on the oldest leaves, the significantly
lower number of species recorded in the island of Correnti meadow is due to the greater exposure
to water movement at that station, which causes more shedding of the oldest leaves. A further
10 years passed before a new study on epiphytic algal communities on P. oceanica leaves was
made [107]. Here the epiphytic flora of the P. oceanica meadow of Vendicari island (Syracuse) was
examined.A total of 78 species (7 Cyanophyta, 47 Rhodophyta, 16 Ochrophyta and 8 Chlorophyta)
were found.

About 10 years later, the epiphytic algal flora of the meadow of the Marine Protected Area
‘Isole Ciclopi’ (Catania) was studied [108]. Epiphytic macroalgae on both leaves and rhizomes
were considered. A total of 73 species (54 Rhodophyta, 13 Ochrophyta and 6 Chlorophyta) were
recorded, of which only 14 (10 Rhodophyta and 4 Ochrophyta) were found on leaves. This number
appears very low compared with those recorded in the above-mentioned meadows occurring along
south-east coast of Sicily, although this is similar to that found in the meadow off Lacco Ameno
(Ischia, Gulf of Naples), where only 19 species were recorded [109].

Finally, patterns of variability in epiphytes of P. oceanica leaves at various spatial scales around
Sicily were investigated [110]. Encrusting red and brown algae, filamentous algae, encrusting
bryozoans, erect bryozoans, hydroids and Foraminifera were the most abundant taxa. Significant
differences in the abundance of taxa were detected among geographical regions (more abundant
on the western coast than the northern and southern coasts of Sicily), although no significant
differences were found between Sicily and the small islands. At smaller scales, variability was
concentrated mostly among leaves 100s of centimetres apart and among meadows a few kilometres
apart. These results suggest that both geographical and local processes are important in structuring
the epiphytes of P. oceanica leaves in this area of the Mediterranean basin.

9. Trophic role

Despite their wide distribution and ecological importance, seagrass ecosystems are still incom-
pletely studied in terms of organic matter pathways and food web structure. The information
available on the trophic ecology of seagrass ecosystems (e.g. the role of herbivory and detritus,
the contribution to littoral fish production, exportation to other ecosystems) is mainly based on
new insights derived from the application of stable carbon and nitrogen isotope analysis. Using
this technique, the role of seagrasses was studied in a semi-enclosed coastal area (Stagnone di
Marsala) [16,111] and adjacent saltworks [112] in the Egadi Archipelago [113] and the island
of Ustica (Vizzini, unpublished data) and along the south-western [114]) and south-eastern [17]
coasts of Sicily. Most of the available information is on P. oceanica because of its large extension,
biomass and associated biodiversity.