  The analysis of benthic assemblages is a valuable tool to describe the
ecological status of transitional water ecosystems, but species are extremely
sensitive and respond to both microhabitat and seasonal differences. The
identification of changes in the composition of the macrobenthic community in
specific microhabitats can then be used as an "early warning" for environmental
changes which may affect the economic and ecological importance of lagoons,
through their provision of Ecosystem Services. From a conservational point of
view, the appropriate definition of the spatial aggregation level of
microhabitats or local communities is of crucial importance. The main objective
of this work is to assess the role of the spatial scale in the analysis of
lagoon biodiversity. First, we analyze the variation in the sample coverage for
alternative aggregations of the monitoring stations in three lagoons of the Po
River Delta. Then, we analyze the variation of a class of entropy indices by
mixed effects models, properly accounting for the fixed effects of biotic and
abiotic factors and random effects ruled by nested sources of variability
corresponding to alternative definitions of local communities. Finally, we
address biodiversity partitioning by a generalized diversity measure, namely
the Tsallis entropy, and for alternative definitions of the local communities.
The main results obtained by the proposed statistical protocol are presented,
discussed and framed in the ecological context.
