Statistical analysis of the distribution of infralittoral Cystoseira populations on pristine coasts of four Tyrrhenian islands: Proposed adjustment to the CARLIT index

The influence of geomorphological features on the distribution of Cystoseira populations along the coasts of four pristine islands in the Tyrrhenian Sea (Italy, central Mediterranean) was studied by means of a model-based statistical analysis. The most relevant trait that determined the presence of these populations was found to be the coastline slope at the level of the infralittoral fringe. Our findings indicate that slopes above 60° reduce the likelihood of Cystoseira communities. The effects of the coastline slope on the CARLIT index are considered and discussed in view of these findings. Pending further studies on the implementation of the CARLIT index in the Mediterranean basin, we suggest that any changes to the procedure or the hasty multiplication of reference sites be avoided, and instead propose a simple empirical adjustment of the EQ values to be able to more accurately monitor coasts with steep slopes using this index.