alexandre506 的鑑定

In CHECK LIST OF BENTHIC MARINE ALGAE FROM CATALONIA (NORTH-WESTERN MEDITERRANEAN) the following Laurencia species are cited:
L. obtusa (Hudson) Lamouroux
L. microcladia Kiitzing
L. paniculata (C. Agardh) J. Agardh
L. papulosa (C. Agardh) Greville
L. pelagosae (Schiffner) Ercegovic
L. pinnatifida (Hudson) Lamouroux

It cannot be L. obtusa, as branching is alternate, not obtuse

Photographed in the intertidal area, although it possibly belongs to the same species as these subtidal individuals:
https://www.inaturalist.org/observations/233924011 and https://www.inaturalist.org/observations/233939826

Not sure at all about the ID. The species is also present in most beaches of the Tarragona coast (Platja Grossa, l'Arrabasada...)

Probably the same species as here: https://www.inaturalist.org/observations/233924027