Page 2 - p_isi_56

Downloaded By: [Furnari, G.] At: 10:31 24 May 2010 250 S. Calvo et al.

In the last few decades, natural disturbances and human activities have caused a worldwide
decline in seagrass ecosystems [3–5] and their protection and conservation are becoming of
primary importance in the environmental legislations of many countries. Seagrass meadows, have,
in fact, already been proposed as a priority habitat under the European Union Habitats and Species
Directive (H&SD 92/43/EEC). Moreover, the Water Framework Directive (WFD 2000/60/EU),
establishng a framework for the protection and improvement of costal waters, considers seagrasses
as biological quality elements, useful in order to assess the ecological status of coastal water bodies.

In the Mediterranean Sea, four native and one invasive true marine seagrass species are present.
Native Posidonia oceanica (Linnaeus) Delile and Cymodocea nodosa (Ucria) Ascherson are
widely distributed forming extensive meadows, while Nanozostera noltii (Hornemann) Tomlinson
& Posluszny and Zostera marina Linnaeus are less common. The invasive Halophila stipulacea
(Forsskål)Ascherson is a Lessepsian species spreading from the Red Sea to the eastern and western
Mediterranean where it has its northernmost distribution in the harbour of Palinuro (Salerno,
Campania) [6].

All five Mediterranean seagrasses have been recorded in the infralittoral zone of Sicily, the
largest island in the Mediterranean with a surface area of ∼25,000 km2. Sicily is located in
the middle of the basin and is surrounded by 14 small islands, which are mainly part of three
archipelagos. The coastline of Sicily, including its small islands, is ∼1600 km long, representing
more than 1/50th of the Italian coastal perimeter.

In Sicily, the beginning of a modern approach for studying seagrasses dates back to the middle of
the twentieth century with studies by Molinier and Picard [7]. In particular, these authors, coupling
observations of the meadows of Sicily with those of meadows along the French and Algerian
Mediterranean coasts, were able to drive general conclusions and to build general hypothesis,
giving rise to the modern Mediterranean seagrass ecology [8,9].

Studies have evolved from an initially qualitative [7,10,11] to a current quantitative level [12–
19]. This transition has been paralleled by a diversification in research topics and implied the use of
new approaches and tools (remote sensing and acoustic techniques, molecular ecology) [20–23].

Here, we summarise here the data available from multiple and diverse information sources,
i.e. scientific literature, reports, web sites. Sources were identified by conducting a web research
using the following search term: (Sicily* or Mediterranean*) and (seagrass* or Halophila stip-
ulacea* or Nanostera noltii* or Zostera noltii* or Zostera marina* or Cymodocea nodosa* or
Posidonia oceanica*). However, studies are at a very local scale and the knowledge of sea-
grasses at a large scale along Sicilian coasts is prevalently confined to the grey literature. In
an attempt to fill this gap, we integrated the literature data with a only partially published data
coming from a databank built in the framework of monitoring programs performed in the last
20 years.

Such information will help us to understand the levels of the environmental threat to
seagrasses in a regional context, which will support the seagrass conservation actions by regional
agencies.

2. Species distribution

The five Mediterranean seagrasses show different degrees of spread and cover in in the infralittoral
zone of Sicilian coasts (Figure 1).

The Lessepsian immigrant seagrass Halophila stipulacea [24] was first found in the eastern
Mediterranean in 1894 [25], remaining restricted to this basin for several decades. The first record
in Sicily (and Italy) dates back to 1988 in Riposto Harbour (Catania) by Villari [26], although
local fishermen claimed that the species was already present on the Ionian coast (Giardini Naxos–
Messina) before 1975 [27]. Later, H. stipulacea showed a progressive colonisation pattern along