The purpose of this paper is to assess the influence of several biotic and abiotic factors on the abundance of waterbirds in
the Grado-Marano Lagoon.
The Grado-Marano Lagoon is situated in the Northeast of the Adriatic Sea with an extension of approximately 160 km<sup>2</sup>.
ASTER satellite images were utilized to classify different types of morphologies and habitat, including sea grass
meadows. Four abiotic factors (total nitrogen, total phosphorous, alkalinity and sediment texture) and three biotic factors
(benthic community, sea grass meadows and waterbird guild abundance) were integrated into a GIS.
A regular UTM grid of square cells (Operational Geographic Units, OGUs), 1km x 1km, was superimposed on the entire
Using the Hierarchical Cluster Analysis (HCA) technique it was possible to delineate ecological units (clusters of OGUs)
and Principal Component Analysis (PCA) was used to reduce the dimensionality of the factors considered. Subsequently,
Correspondence Analysis (CA) was used to examine the relationship between waterbird guild abundance and ecological