Dati preliminari sulla variabilità spazio-temporale di Paracentrotus lividus nell’ AMP “Capo Gallo Isola delle Femmine”

Population structure of the sea urchins Paracentrotus lividus and Arbacia lixula across a depth gradient

Sea urchins are considered to have a paramount role in structuring rocky shallow communities. Under certain conditions, grazing by sea-urchins has been reported to produce a shift from macroalgae-dominated communities to barren habitat dominated by encrusting algae. However, this process is not recorded at all depths. The effect of depth on the structure of the sea-urchin populations may be thus a key feature to understand the origin and maintenance of the barren habitat within certain depths. In the present study, the structure of Paracentrotus lividus (Lam.) and Arbacia lixula (L.) populations are analyzed across a depth gradient in the Ustica Island MPA (NW Mediterranean), where the barr…

Mapping the distribution of urchin barren grounds using sidescan sonar: the experience of the “Plemmirio” MPA

In the Mediterranean Sea, high densities of the sea urchins Paracentrotus lividus and Arbacia lixula may promote and maintain formation of areas overgrazed by sea urchins, usually referred to as urchin barrens, leading to drastic changes in ecosystem functioning. Urchin barrens are habitats of low primary production and habitat structure, that negatively affect local biodiversity. At Plemmirio MPA, abundance of both sea urchin species increased dramatically after the start of enforcement in 2005 consequently triggering the formation of “barren” seascape, evidence of a desertification process. This study focuses on the results of a high-resolution Side scan sonar (Klein 3900) surveying carri…