Shallow beds
Index
The shallow beds of the Venetian Lagoon are extensive submerged areas at low depth. They play a key role in maintaining water quality by promoting the settling of suspended particles and contributing to natural purification. Two main types can be distinguished: intertidal areas, such as tidal flats (velme), and subtidal areas, which remain permanently submerged.
Tidal flats are mostly underwater, emerging only during exceptionally low tides. Made up mainly of fine sediments, they represent transitional environments between saltmarshes and deeper beds. Their shape is constantly reshaped by currents and tides, under the combined effects of erosion and sedimentation. Tidal flats provide essential ecological functions, offering habitat to numerous benthic organisms such as molluscs, crustaceans and polychaetes, which in turn are an important food source for fish and waterbirds. They also favour the growth of algae and seagrasses, helping to stabilise the sediment and reduce water turbidity.
Shallow beds more generally include surfaces with different substrates and vegetation, which host diverse benthic communities and serve as feeding, nursery and sheltering grounds for many fish species. Some areas are characterised by seagrass meadows of Zostera marina and Cymodocea nodosa, which oxygenate the water, stabilise the sediment against erosion and create complex habitats that support particularly rich biodiversity. Other areas are dominated by algal mats of green and red macroalgae, which can thrive in nutrient-rich conditions. Others are bare, with sandy or muddy bottoms. The distribution of these seabeds depends on hydrodynamic factors influencing salinity and temperature gradients, nutrient and particle availability, water quality and human pressure, all of which directly affect the biological productivity of the lagoon ecosystem. In turn, this mosaic of habitats shapes the composition of benthic and fish communities.
Maintaining such habitat diversity is therefore crucial to safeguarding biodiversity.
In some shallow-water areas, Manila clam (Ruditapes philippinarum) aquaculture and harvesting are practised. These zones, with sandy and muddy sediments, are well suited to clam growth. Clam farming expanded rapidly in the late 1980s and has since made an important contribution to the local economy. However, intensive practices have caused environmental problems such as seabed alteration, reduced biodiversity and the spread of invasive species. For this reason, sustainable management of clam farming is essential to balance economic output with environmental protection.