Ecological modelling: from the biosphere to the everyday data gathering; filling the gap.
Biosphere, according to many authors, can be considered as a system characterised by control mechanisms, which allow the maintenance of its stability. If the Biosphere is a complex object, the coming out of the equilibrium will have as a result a rapid change which cannot be controlled and whose results cannot be foresighted. Modelling is, for this reason, desperately needed. A general mathematical modelling suggested that the Biosphere evolution be characterised by periods of stability and instability, which are related to the connections between its components. These components, both living and not living, are connected by feedback relationships maintaining stability. From this model a general ecosystem modelling was developed which was first applied to a very peculiar situation i.e. that of the hydro-thermal marine vents. The hydrothermal ecosystem is, anyway, a very peculiar one and it can be considered also a micro-biosphere with its own sources of energy not related to sun radiation. For this reason it was possible to make a correlation between these very peculiar ecosystems and the Biosphere. More difficult it is to relate the modelling of the light depending ecosystems, which are, on the contrary, of great interest because they are directly linked to the Biosphere and objects of quite everyday data gathering. Usually the description of ecosystems, which is proposed by the everyday operative task of collecting data, and which represents the widest source of data for modelling, is related to the quality of waters or air. In this way we have to find tools correlating the data routinely investigated and the general model proposed. Here we present the other side of the approach, a local investigation of the qualities of water, with the hope to make a proposal for the ecologists to carry on their job also taking into consideration the problem of ecosystems modelling. An evaluation study of the environmental condition of Fine River, based on the E.B.I. method (Extended Biotic Index) applied to macroinvertebrates was carried out in 2002. Seven sampling locations were selected along the main flow and two were selected on the two most important tributaries that flow into the Fine, the Savalano and the Pesciera-Marmolaio. On the upper part of the river two locations were selected, up-river the artificial reservoir of S. Luce, and five locations were selected in the intermediate and potamal part. 43 taxa of macroinvertebrates have been detected, among them 4 Plecoptera and many Ephemeroptera assembled by environmental variables. Chironomids have been detected in all the locations. The multivariate analysis with Multidimensional Scaling (MDS) applied to the samples of the potamal part location shows variability in the macroinvertebrates assemblage. The E.B.I. method resulted in a good quality of the water on the upper part of Fine River. The E.B.I. results, corresponding to the second Quality Class (Q. C.), were determined by the presence of the Plecoptera Chloroperla and several Ephemeroptera. These taxa are considered among the most sensitive to pollution. Downriver of Santa Luce reservoir, the water condition gets worse (3rd Q. C.), and this remains consistent along the intermediate and potamal part of the river, though it is never to be considered really bad. Water quality of the Savalano results between the second and third Q. C., while the situation of the Pesciera that flows waters of really bad quality into Fine River is to be considered serious. The F7 station (Polveroni), situated at the closing section of the basin, proves to be suitable to summarise the general conditions of the river. Finally a proposal to use the model developed for the hydrothermal vents for a provisional modelling to recover the water quality in the investigated ecosystem is presented and discussed.
Banchetti
Rosalba
R
Department of Ethology, Ecology and Evolution, University of PISA. rbanchetti@deee.unipi.it
Marsili
David
D
Galleni
Lodovico
L
D000818:Animals; D003625:Data Collection; D004463:Ecology; D017753:Ecosystem; D004734:Energy Metabolism; D005618:Fresh Water; D007313:Insecta / Q000502:physiology; D008954:Models, Biological; D045483:Rivers; D014876:Water Pollution