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Investigating on the occurrence of Paracentrotus lividus in rocky and Posidonia oceanica habitat

Pinna, Stefania and Ceccherelli, Giulia and Sechi, Nicola (2007) Investigating on the occurrence of Paracentrotus lividus in rocky and Posidonia oceanica habitat. In: Cambiamenti globali, diversità ecologica e sostenibilità: atti del 16. Congresso nazionale della Società Italiana di Ecologia, 19-22 settembre 2006, Viterbo-Civitavecchia, Italia. Parma, Società Italiana di Ecologia. p. 4. Conference or Workshop Item.

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The sea urchin Paracentrotus lividus (Lamarck) is the most common grazer in the Mediterranean infralittoral that at high densities overgrazes complex algal assemblages turning them into barren areas. This study has the aim to investigate whether abundance and population structure of P. lividus is consistent between rocky boulders and Posidonia oceanica habitat. At this aim, we have sampled P. lividus at six sites in the Gulf of Alghero (North West Sardinia), 3 fished (sea urchin are harvested) and 3 controls (no harvest is allowed) and at each site the two habitats, 6-10 m deep, were considered. For each combination site x habitat 10 replicates were taken. Density of P. lividus was assessed using quadrats of 1 x 1 m. The size of 20 individual (test diameter without spines) per site was measured by means of a calliper (1#1 0.1mm). Sea urchins, finally were grouped into size classes to examine frequency distributions. Sampling was performed at the end of a harvesting period (April-May 2006). Analyses of data have highlighted a significant variability for both response variables among sites while in Posidonia oceanica habitat a lower density and a higher size were found rather than in rocky habitat. Further data collected at three types of Posidonia oceanica (patches close to rocky habitat, far from rocky habitat and patches bordered by sediment) suggest that the abundance of adults in the seagrass is probably sustained by immigration from the rocky habitat.

Item Type:Conference or Workshop Item (Poster)
ID Code:705
Uncontrolled Keywords:MPA, Paracentotus lividus, Posidonia oceanica, rocky habitat, seaurchin harvest, North-West Sardinia, Gulf of Alghero
Subjects:Area 05 - Scienze biologiche > BIO/07 Ecologia
Divisions:001 Università di Sassari > 01 Dipartimenti > Scienze botaniche, ecologiche e geologiche
Publisher:Società Italiana di Ecologia
Deposited On:18 Aug 2009 10:03

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