The spatial dynamic of Posidonia oceanica meadows is a process extending over centuries. This paper shows evidence of the natural dynamics of P. oceanica “shifting intermattes” or “sand corridors” (hereafter SCs): unvegetated patches within a dense meadow. We studied features and temporal evolution (2001-2015) of 5 SCs in the Calvi Bay (Corsica) at 15 m depth and followed the characteristics the P. oceanica meadow lining the edge of patches. All SCs show a similar topography. The eroded side is a vertical edge where roots, rhizomes and sediments are visible, when on the opposite colonized side, the sand is at the same level as the continuous meadow. The vertical edge reaches a maximum height of 160 cm and is eroded by orbital bottom currents with a maximum speed of 12 cm.s-1, the erosion speed ranging from 0.6 to 15 cm.y-1. SCs progress toward the coastline with a mean speed of 10 cm.y-1, the rate of colonization by P. oceanica shoots ranging from 1.5 to 21 cm.y-1. We calculated that the studied SCs would reach the coastline within 500 to 600 years. We finally discuss the implication of such dynamic in the framework of meadows’ colonization assessment and the seascape dynamic.

The LIMA index conveys the environmental interest and quality of the landscape formed by the Mediterranean benthos, ranging from 0 to − 40 m, in numerical format. The LIMA index allows a comparison spatially and temporarily between sites. It is a comprehensive index which is easy to implement and is composed of two factors: a topographical description (classification of 15 typologies) and a biological description (the presence or absence of some thirty species or groups of structuring, remarkable and invasive species). The LIMA index has been validated in the Bay of Calvi (Corsica-France) where it varies between 0.31 and 0.79 on a scale of 0.00-1.00.

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In the Mediterranean sea, the high commercial value of lobsters has an important economical impact. Palinurus elephas and Palinurus mauritanicus are distributed in the Western Mediterranean sea and in the North-Eastern Atlantic Ocean. Overfishing is one of the principal causes of spiny lobsters rarefaction. Palinurus species have decreased in many sectors of the Mediterranean sea and most productive fisheries occurred around islands. For this reason many countries have made up a program on the stock preservation. We report results of phylogenetic analyses based on nucleotide sequence data from two regions of the mitochondrial genome, the large-subunit ribosomal RNA (16S) and the cytochrome oxidase I subunit (COI) in Panulirus elephas and Panulirus mauritanicus. In this studie we also included sequences of these gene regions for 28 taxa within the genus Panulirus and Jasus. All the methods used in this study (Neighbor-joinig, Network Median joining) support the phylogenetic position of Palinurus between Panulirus and Jasus.