Abstract
The present research continues the study of benthic diatoms colonizing artificial substrates kept submerged in brackish water. For this purpose samples from three stations of “Valle Sparesera” (an experimental fish pond of the Venice Lagoon) were studied. Periphyton and various environmental factors were measured. The results show that the genera fouling fresh substrata are abundant, especially where there is considerable water movement. This however does not correlate with data on populations per unit area. The most abundant and constantly present species were Amphora exigua, Synedra tabulata and two species belonging to the genus Cocconeis (C. molesta, C. scutellum). The position of vertical or horizontal exposed slides had no influence upon the quantity of periphyton. Comparison with the phyto-plankton carried out over the same period showed that, contrary to the usual situation, the highest development of phytoplankton occurs before that of benthic diatoms.