Un approccio modellistico allo studio dell'accrescimento fogliare in Posidonia oceanica
Author(s)
Di Dato, Paola
Date Issued
March 15, 2010
Type
Doctoral Thesis
Abstract
In coastal marine environments, seagrasses are key species constituting complex ecosystems
that make a considerable contribution to the stability and conservation of the coastal
environment.
Thanks to its ecological role (biological indicator of environmental quality, high
productivity, stabilization of sedimentation processes and geomorphologic conservation of
the coastal area, habitat and nursery area for numerous species of commercial interest) the
Posidonia oceanica is the most important species, and its meadows are considered a primary
habitat of general interest by the Council Directive on Habitat (92/43/CEE).
Over the last century, the increasing human impact (demographic pressure, urbanization,
industrialization, pollution and global climate change) has meant that coastal ecosystems and
particularly those of the Posidonia oceanica, have been among those most threatened and
subject to heavy degradation. As a consequence, Posidonia oceanica is now included in the
list of endangered species included in the Barcelona Convention.
This situation has made it all the more necessary to deepen knowledge of the biology and
physiology of this plant, also with the aim of understanding the complex mechanisms
underlying its ecosystem.
With this in mind, this study is part of a multidisciplinary research project being carried out over a number of years and still ongoing. It consists of the explantation, transplantation,
maintenance and monitoring of Posidonia oceanica specimens in the stretch of sea between
Civitavecchia (RM) and Santa Marinella (RM). This project has provided the opportunity to
analyze an enormous amount of leaf material producing a remarkable bank of phenological
data.
The availability of such a vast quantity of phenological information, together with data
accumulated thanks to intensive efforts to recover available historical databases, provided
the stimulus to carry out a preliminary analysis of data relating to leaf growth rates for the
meadow under study. Above all, however, the objective was to attempt to formalize an
analytical model able to describe the growth processes in P. oceanica leaves through a
simulation of the phases of expansion, longevity and biological aging of its leaves.
It should be noted that the significant differences between Posidonia oceanica and other
types of seagrass, in physiological terms as well as in terms of their growth patterns, have
made and continue to make it extremely difficult to apply existing models or those
developed for other types of seagrass to Posidonia oceanica.
The aim, therefore, of this thesis was to develop a pathway of analysis and elaboration of the
processes of expansion and erosion of P. oceanica leaves, with the ultimate objective being
the production of a modelling tool that could be implemented “ad hoc” and that was able to
describe the growth processes and provide useful information for the comprehension of the
mechanisms at its basis.
Although the supposed model does not provide a “whole-plant” approach, it can certainly be
considered as the first essential component of a more complete and complex model in which
the leaf part may be complemented by a rhizome growth model in the near future.
Comparison of the results obtained from the simulation with the data observed reveals that
this model provides a reasonable representation of the seasonal growth cycle of the leaves.
Nevertheless, the less satisfying performance in the simulation of the brown tissue, calls for
an improvement of the calibration phase and that of the optimization of the model’s
parameters, suggesting the application in the near future of a calibration process based on the
development of other tools as the genetic algorithms.
On the other hand, it is also true that the processes at the basis of the expansion and erosion of P. oceanica leaf shoots are not only extremely complex, but also little-known.
The difficulties demonstrated in this study, in attempting to efficiently and reliably simulate
a series of processes whose dynamics are still partially unknown, would suggest or even
impose the need to develop field studies more carefully, with the aim of broadening our
understanding of the mechanisms underlying such growth processes.
In summary, the model presented is the first, perfectible step in a very complex and
potentially developable mosaic, able to represent the growth dynamics of a fundamental
component of the coastal marine ecosystem.
It is not out of the question, therefore, that if correctly modulated, it could even be a useful
tool in the regulation of anthropic intervention on the coastal ecosystems such as Posidonia
oceanica.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
Subjects
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