Preprint volume - SIBM

Pre-print Volume - Posters
BENTHOS COMMITEE
R. BEDINI*, B. BOCCIA, F. BATISTINI, M. PERTUSATI, J. PISTOLESI
Istituto di Biologia ed Ecologia Marina, Piazza Bovio - 57025 Piombino, Italia.
museomare@biomare.it
SPATIAL AND TEMPORAL VARIABILITY
OF CRUSTACEA ASSEMBLAGES OF POSIDONIA OCEANICA
MEADOWS OF NORTHERN TUSCANY
VARIABILITÀ SPAZIALE E TEMPORALE DEI POPOLAMENTI
A CROSTACEI DELLE PRATERIE DI POSIDONIA OCEANICA
DELLA TOSCANA SETTENTRIONALE
Abstract – The present paper reports data about a study carried out along the northern coasts of Tuscany.
Crustacea assemblages were sampled four times throughout one-year period at two depths. Results showed
an interaction between depth and date to determine the composition and abundance of assemblages.
Key-words: Crustacea, depth, Posidonia oceanica, Tuscany.
Introduction – Vagile fauna represents an important component of seagrass ecosystem
(Ledoyer, 1966, 1968). In fact, meadows offer refuge and nutriment to a lot of taxa that
contribute to create complex trophic nets. Vagile fauna could be highly variable in
space and time. In fact, vagile fauna normally shows a temporal dynamic related both
to life cycles of organisms and to changes in the structure of meadows. Patterns of
spatial variability may be related to depth or other gradients of environmental factors
acting in the meadows. Crustacea are one of the main taxa of vagile fauna associated to
seagrasses (Mazzella et al., 1989). The aim of the present paper is to show results of a
study performed to evaluate patterns of spatial and temporal variability of Crustacea
assemblages of Posidonia oceanica (L.) Delile meadows of Tuscany.
Materials and methods – The study was carried out along the northern coasts of
Tuscany, (north-western Mediterranean Sea). Two depth ranges were considered: 5-10
m (corresponding to the upper limit of meadows) and 20-25 m (corresponding to the
lower limit of meadows). Samplings were carried out at 4 dates during one-year period.
For each depth and date, 3 sites were sampled and 3 replicated samples were collected
in each site. Organisms were sampled by hand-towed net (Gambi & Dappiano, 2003).
For each sample, taxa were determined and the abundance of each taxon was expressed
as number of organisms. Data were analyzed by PERMANOVA analysis (Anderson,
2001) with Depth (shallow vs. deep) as fixed factor, Date (4 levels) as random factor
crossed to Depth, Site (3 levels) as random factor nested in the interaction between
Depth and Date. SIMPER test was used to detect species responsible to multivariate
patterns.
Results – A total of 85 taxa of Crustacea was found in the meadows. PERMANOVA
analysis showed a significant interaction between Depth and Date (pseudo-F=2.256,
P(perm)=0.007). In fact, differences between depths were significant only in springsummer
dates and differences between dates were significant only in shallow
assemblages. The SIMPER test showed that Hippolyte inermis, Gnathia maxillaris,
Palaemon xiphias, Copepoda and Misidiacea were the main taxa contributing to
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