Restoration Project

Università di Sassari - La Pelosa

Restoration Objective:

This study aimed to evaluate the effect of harvesting commercial P. lividus on the shift between barren and Cytoseira bed habitats.

Site Selection Criteria:

Sites were selected with boulders, for use as the experimental units. On each boulder, a patch of Cytoseira and turf algae was surrounded by encrusting corallines.

Cause Of Decline:

In the Mediterranean Sea, beds of canopy-forming algae of the genus Cystoseira are the dominant assemblages of shallow subtidal rocky habitat in environments under low anthropogenic disturbance. Overgrazing by the sea urchin Paracentrotus lividus related to overexploitation of predator fishes is considered a major cause of shifts from Cystoseira beds to barren states in the Mediterranean Sea.

Key Reasons For Decline:


Scientific Paper

Effect of sea urchin human harvest in promoting canopy forming algae restoration

L. Piazzi, G. Ceccherelli, , Estuarine, Coastal and Shelf Science, Vol. 219.


Università di Sassari

Site Observations:

Observation Date

1st Nov 2016 – 1st Nov 2017

Action Summary:

Six areas of 20m2 about 50m distant from each other were selected and randomly assigned in groups of two to one of the following treatments: natural urchin density, removal of all sea urchins and removal of only commercial Paracentrotus lividus (>50mm test diameter). In each area, three boulders were considered as replicates and, at the start of the experiment, the number of C. brachycarpa individuals in the patch was evened to 20 by removing excess thalli. Treatments were maintained from November 2016 to November 2017 and sea urchins were removed monthly as necessary.

Lessons Learned:

Removal of all sea urchins led to the greatest increase in revegetation, however removal of only commercial P. lividus also resulted in a significant change. However, the change was mainly in turf algae rather than Cytoseira.

Project Outcomes:

At the end of the study area, in treatments where all urchins were removed the algal surface area increased in cover by approximately 250%, although this change was mostly related to the turf assemblages associated with C. brachycarpa. In treatments where only commercial P. lividus was removed, increase in cover was 200%.

Key Reasons For Decline:


Area of Restoration (In Square Metres)


Indicator Data:


Ending Value:

Starting Value:

Adult Kelp Count

Cost Currency:USD