[eng] The human impact on the global environment has caused a fast regression of the seagrass
meadows, which are a crucial part of the marine ecosystem. The aim of this work is to
propose a microscopic clonal growth model of seagrass growth to understand better the
dynamics of the meadows and the factors that affect their development. In particular,
the proposed model will address the problem of two seagrass species interacting in the
same spatial region. The species used will be the Mediterranean endemic species of
seagrass Cymodocea nodosa and Posidonia oceanica. To build the final model, the first
step is to start from the study of models of clonal growth of a single seagrass specie
without interaction. The results show that the fate of the patches depends on the difference
between the intrinsic branching rate and the mortality rate. Initially, the growth of the
patch is governed by a branching independent process and it changes to a radial linear
expansion after some years, when a plateau density is reached. We have extended the
models adding the presence of a local interaction. This local interaction is introduced
through a dependence of the total branching rate with the local density. A parameter study
has been used to identify different regions of stable populated solutions or stable extincted
solutions. This acts as a basis for the development of the novel model of cross-interaction
between the two seagrass species. Two variants of the model have been proposed: one that
gives equal weight to both seagrass species (ECI) and the other that gives more weight to
Posidonia oceanica due to its biological characteristics (DCI). The different cases of study
reveal that the overall dynamics of the patches of seagrass is determined by the intrinsic
branching rate of the seagrass specie. Moreover, the cross-interaction between species
influences the density of the patches. In addition, we have determined that ECI displays
more reasonable dynamics than DCI. The work is expected to give the tools and the basis
to more extended models of two interacting seagrass species