Application of a new bioindex based on hard substrate biocoenosis for the evaluation of the lagoon quality

This research was based on the study of the fouling in the Lagoon of Venice and its aim was to verify the reliability of an index of environmental quality applied to four stations of the Lagoon. Such index has been developed through the collection of physico-chemical and biotic data and the study of their interrelation. From June 2007, panel systems, each one represented by a steel and a wood panel (20 x 15 x 2.5 cm), were immersed in four different stations in order to collect data regarding a representative area of the Lagoon in a period – summer – which, although limited, corresponded to the maximum development and differentiation of the biocoenoses. Pictures of the panels, to control the ecological succession of the macrofouling community of hard substrates covering the panels, and values of physico-chemical parameters of the seawater, like temperature, pH and salinity were collected each month. Data were introduced in the bioindex to describe the status of health of the lagoon seawater in the four stations. The main work consisted in the biotic data processing, through the analysis of the digital photos of the panels for the recognition of the species, their number and the covered area on the panels. The index of environmental quality under examination results useful for evaluating the status of health of the lagoon seawater by means of a cheap and effective system. Results were compared with those previously obtained and have supplied confirmation of the utility of this bioindex, in spite of differences probably due more to little year's climatic change than significant variations in local parameters.