Assessing the human footprint on the sea-floor of coastal systems: the case of the Venice Lagoon, Italy

Abstract

Coastal systems are among the most studied, most vulnerable, and economically most important ecosystems on Earth; nevertheless, little attention has been paid, so far, to the consequences of human activities on the shallow sea-floor of these environments. Here, we present a quantitative assessment of the effects of human actions on the floor of the tidal channels from the Venice Lagoon using 2500 kilometres of full coverage multibeam bathymetric mapping. Such extended dataset provides unprecedented evidence of pervasive human impacts, which extend far beyond the well known shrinking of salt marshes and artificial modifications of inlet geometries. Direct and indirect human imprints include dredging marks and fast-growing scours around anthropogenic structures built to protect the historical city of Venice from flooding. In addition, we document multiple effects of ship traffic (propeller-wash erosion, keel ploughing) and diffuse littering on the sea-floor. Particularly relevant, in view of the ongoing interventions on the lagoon morphology, is the evidence of the rapid morphological changes affecting the sea-floor and threatening the stability of anthropogenic structures.

Tidal inlets in the Anthropocene: Geomorphology and benthic habitats of the Chioggia inlet, Venice Lagoon (Italy)

“…The anthropogenic submerged litter and abandoned fishing gear are an emerging issue for the society and for marine sciences: however, most of the available researches are based on photograph/video surveys (e.g. Schlining et al ., ; Pham et al ., ) or on samples collected by seabed trawling (Kammann et al ., ; Grøsvik et al ., ; Maes et al ., ; Madricardo et al ., ) being mainly focused on plastic/glass rubbles. This study also confirms that MBES surveys can be a useful aid in mapping the density distribution of macro‐litter and wrecks in shallow coastal areas.…”

“…Humans are altering the planet, including long‐term global surface geologic processes, in such a way that a new geological epoch called the Anthropocene has been introduced, although still waiting to be officially recognized (Hamilton, ; Finney and Edwards, ). While the study of land‐use changes in the Anthropocene has considerably advanced (Tarolli, ; Brown et al ., ), much less is known about the human impact on the seafloor, particularly in coastal areas (Mayer et al ., ; Madricardo et al ., ).…”

Physics-based Bathymetry and Water Quality Retrieval Using PlanetScope Imagery: Impacts of 2020 COVID-19 Lockdown and 2019 Extreme Flood in the Venice Lagoon

“…This is because the tidal effects can vary spatially that can introduce a regionally variable depth offset across the study area. Furthermore, the bed topography in the Venice lagoon is subject to major changes over time due to tidal effects and human-induced activities [72]. For instance, the morphodynamics of a shallow tidal system such as the Venice lagoon is highly influenced by sediment transportation in the presence of ship and boat traffic [38,64,71].…”

How to Deal With Seafloor Marine Litter: An Overview of the State-of-the-Art and Future Perspectives

“…Mayer et al (2007) conducted specific experiments showing that the resolution of multibeam sonar combined with 3D visualization techniques provided realistic looking images of mines and mine-like objects that were dimensionally correct and enabled unambiguous identification on a sandy seafloor. More recently, Madricardo et al (2019) used high resolution MBES data (up to 5 cm resolution to map objects larger than 0.8 m) to assess the mean abundance of marine macro-litter in a large area of the Venice Lagoon and to identify marine litter hot spots (see Figure 2a). The average area per diem covered was 0.68 km 2 /day with a mapping rate of 0.097 km 2 /h (Madricardo et al, 2017).…”