Seaweed distribution in Calvi bay : from 35 years of temporal changes towards R modelling of distribution maps.

During 1978-1979 and 1991-1992 periods, the STARESO and Liège University initiated an early systematic monitoring of seaweed communities along 24 reference transects (0-15 m) in Calvi bay (Corsica). This defined important historical references for long term dynamical studies of that remarkable coastal environment. In 2013-2015, new records of macroalgae specific composition and cover rate were collected in these reference sites, as along additional and deeper transects (0-40 m).

Macroalgal distribution profiles are compiled to allow exploitation by R codes for several goals :

a) Allow an improved synthesis and vision on statistics associated to distribution profiles, from average profiles at bay scale to remarquable sub-areas, particularly for the main species considered for primary production studies as the role of this biological compartment is most probably underestimated in that concern (i.e. Cystoseira (C.) brachycarpa, Dictyota dichotoma, Stypocaulon scoparium). The tools developed will also ease exploration of any questions arising concerning other important species, as for instance in terms of remarquable biological habitats (C. spinosa, C. fimbriata, ...), environmental sensitivity (C. amantaceae var. stricta), invasive trends (Caulerpa racemosa), massive blooms (filamentous algae), niche of apparently stabilized allochtone species (Sargassum sp.) or ecological ranges of species with particular biochemical properties (Janioides, Codium,...).

b) Assess recent changes of species distribution in comparison with historical data, mainly concerning species having displayed significant changes between 1978-1979 and 1991-1992.

c) Exploit and adapt R species distribution modelling tools to extrapolate continuous maps of macroalgae species and communities throughout the whole Calvi bay.