Preprint volume - SIBM

Pre-print Volume - Oral presentations
Topic 1: BIODIVERSITY AND CONSERVATION SCIENCE: CONTRIBUTING TO MANAGEMENT
Results show that surface hydrodynamism is the main environmental factor of
dissimilarity between the two areas, despite the scarce distance (less than 80 meters)
which separates them. Benthonic community of northern area, exposed to winter winds
action, is more heterogeneous; on the contrary, the community of the southern one
seems to be more influenced by the type of substratum rather than by the
hydrodynamism (Fig. 3).
Fig. 2 – n-MDS Analysis. Samples relevant to N area, in grey; samples relevant to S area, in black.
Continuous line separates the two areas, dashed line separates the two types of substratum.
n-MDS Analysis. In grigio, i campioni relativi all’area N; in nero, i campioni relativi all’area
S. La linea continua evidenzia la separazione tra le due aree, mentre il tratteggio separa i due
tipi di substrato (area S).
The abundance (number of specimens) of the species typical of the photophilic algae
biocoenosis (Gastropods Bittium latreillii, Bittium reticulatum, Cerithium vulgatum,
and Polychaetes Polyophthalmus pictus, Platynereis dumerilii and Syllis prolifera),
present in both areas, is another of factors which differentiate the northern and southern
benthonic community, such as Symper Analysis demonstrates. Dissimilarity is evident
in Spring, when hydrodynamic conditions are more marked and different between
areas.
With respect to Posidonia oceanica, the study shows a progressive and deep lower
limit (-35,7 m in N area, and -36 m in S area). Meadows are well-preserved, as shoots
density data demonstrate in upper, middle and lower zones (Pergent, 1995 in Buia et
al., 2003). Disturbance indices were observed in the upper zone of the both meadows,
emphasized by sandy areas in which the plant is absent. It is possible to hypothesize
that the disturbance is the consequence of high hydrodynamism in N area and the
human impact in the S one.
Pinna nobilis, present in both the meadows, constitutes a population in the S area,
where 29 juvenile clams are counted. The length of biggest valve vary between 7,9 and
26,7 cm, the width between 7,2 e 23,5 cm. The specimens are settled between -3,2 and
-6,1 m.
Conclusions – For the first time a preliminary analysis of the marine benthonic
community of the Enfola istmus has been performed. In future, data on algal
biodiversity, streams trend, and human impact need to be studied in detail as well as
the communities of the lower infralittoral zone. Nevertheless, the presence of a rich
biodiversity and species ascribed to Habitat Directive (Posidonia oceanica and Pinna
nobilis) must be an incentive to preserve the marine areas. The Laboratory Zoology
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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