Preprint volume - SIBM

Pre-print Volume - Posters
Topic 2: MARINE ORGANISMS AND ECOSYSTEMS AS MODEL SYSTEMS
include animal components. To assess differences in sea urchin density, a
PERMANOVA analysis including Species (fixed, 2 levels: P. lividus and A. lixula),
Year (fixed, 4 levels: ’06,’07,’08,’09) Protection (fixed, 2 levels A, C) and Site
(random, 2 levels) factor was performed, while the PERMANOVA of benthic
assemblage cover included Year, Protection and Site factor.
A Zone
A 1
B Zone
A
C Zone
1 Km
Fig. 1 – Sampling sites at the MPA “Isola di Ustica”: A1, A2, C1 and C2. Siti di campionamento nell’AMP “Isola di Ustica”: A1, A2, C1 and C2. 2
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
127
N
Ustica Island
C 2
Results – Density of both sea urchin populations was lower in 2009 than in 2006. P.
lividus and A. lixula densities ranged between 4±0.5 ind./m 2 and 3.35±0.3 ind./m 2 ,
respectively, in 2006 and 0.5±0.1 ind./m 2 and 0.6±0.0 ind./m 2 in 2009. During this
decrement of both sea urchins, a benthic algae shift from Corallinales (barren state) to
erect macroalgae was observed. PERMANOVA showed only an important interaction
between “Year x Site” terms of both sea urchin density and benthic assemblage. For
every site, Pair-Wise tests confirmed the important effect Year on the studied variables.
Conclusions – No protection effect on sea urchin abundance was detected. P. lividus
and A. lixula showed a strong decrement within both take and no-take zones. Multiple
natural control factors (like low sea urchin recruitment and natural predation) may
have provoked the drop of sea urchins abundance. This change in sea urchin
abundances likely promoted the flourishing of erect macroalgae in the upper
infralittoral of Ustica MPA. These results offer new tips of reflection for a simple
cascade trophic model in Mediterranean rocky infralittoral systems.
References
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GIANGUZZA P., CHIANTORE M., BONAVIRI C., CATTANEO-VIETTI R., VIELMINI I.,
RIGGIO S. (2006) - The effects of recreational Paracentrotus lividus fishing on distribution
patterns of sea urchins at Ustica Island MPA (Western Mediterranean, Italy). Fish. Res., 81: 37–
44.
STENECK R.S., DETHIER M.N. (1994) - A functional group approach to the structure of algal
dominated communities. Oikos, 69: 476-498.
C 1