[Venetian word, derived from the dissimilation of the word “melma” (mud)]. Part of the lagoon bed that remains completely submerged during the “acque piene” (high tide waters). The mud flats correspond to the lowest parts of the flattened rises that are spread in the complex net of lagoon canals. In Venice lagoon the mud flat has no vegetation. It is a normally submerged area that emerges in particular conditions of low tide. It was formed by the sediments transported by both river and sea currents, that deposited on the low beds at the borders of the canals. It is characterized by a muddy and sandy substratum. The mud flat environment is even more selective than that of the salt marsh, because of the large variations in the salinity and in the oxygenation due to the periodical submersions. Some animal organisms, as segmented worms and molluscs, take shelter in the substratum when the tide decreases and the mud flat is then left uncovered. The typical vegetation association of these environments is the Zoosteretum noltii (Zostera Noltii and Zostera Nana) and Entheromorpha algae and other green algae as ulva can also be found.
Source: Taken from De Agostini - Sapere.it