COVID-19 lockdown measures reveal human impact on water transparency in the Venice Lagoon

Abstract The lagoon of Venice has always been affected by the regional geomorphological evolution, anthropogenic stressors and global changes. Different morphological settings and variable biogeophysical conditions characterize this continuously evolving system that rapidly responds to the anthropic impacts. When the lockdown measures were enforced in Italy to control the spread of the SARS-CoV-2 infection on March 10th 2020, the ordinary urban water traffic around Venice, one of the major pressures in the lagoon, came to a halt. This provided a unique opportunity to analyse the environmental effects of restrictions to mobility on water transparency. Pseudo true-colour composites Sentinel-2 satellite imagery proved useful for qualitative visual interpretation, showing the reduction of the vessel traffic and their wakes from the periods before and during the SARS-CoV-2 outbreak. A quantitative analysis of suspended matter patterns, based on satellite-derived turbidity, in the absence of traffic perturbations, allowed to focus on natural processes and the residual stress from human activities that continued throughout the lockdown. We conclude that the high water transparency can be considered as a transient condition determined by a combination of natural seasonal factors and the effects of COVID-19 restrictions.

[1]  S. Mallapaty.  What the cruise-ship outbreaks reveal about COVID-19 , 2020, Nature.

[2]  E. Wolanski,et al.  The Role of Turbulence in the Settling of Mud Flocs , 1992 .

[3]  Kuyukov Vitaly,et al.  A Single Algorithm , 2016 .

[4]  M. Ghezzo,et al.  Assessing hydrological effects of human interventions on coastal systems: numerical applications to the Venice Lagoon , 2012 .

[5]  F. Barbariol,et al.  Modeling ship-induced waves in shallow water systems: The Venice experiment , 2018 .

[6]  P. Ricciardi,et al.  Lockdown for CoViD-2019 in Milan: What are the effects on air quality? , 2020, Science of The Total Environment.

[7]  T. Soomere,et al.  The effects of ship wakes in the Venice Lagoon and implications for the sustainability of shipping in coastal waters , 2019, Scientific Reports.

[8]  G. Putoto,et al.  COVID-19 in Italy: momentous decisions and many uncertainties , 2020, The Lancet Global Health.

[9]  L. Zaggia,et al.  Freshwater discharge from the drainage basin to the Venice Lagoon (Italy). , 2005, Environment international.

[10]  Saša Raicevich,et al.  Mechanical clam dredging in Venice lagoon: ecosystem effects evaluated with a trophic mass-balance model , 2003 .

[11]  Gianpiero Cossarini,et al.  Response of Venice Lagoon Ecosystem to Natural and Anthropogenic Pressures over the Last 50 Years , 2010 .

[12]  Indirect Effects , 2020, Do Running Mates Matter?.

[13]  A. Tobías,et al.  Changes in air quality during the lockdown in Barcelona (Spain) one month into the SARS-CoV-2 epidemic , 2020, Science of The Total Environment.

[14]  G. Onder,et al.  Case-Fatality Rate and Characteristics of Patients Dying in Relation to COVID-19 in Italy. , 2020, JAMA.

[15]  P. Mason,et al.  Defining boat wake impacts on shoreline stability toward management and policy solutions , 2019, Ocean & Coastal Management.

[16]  Nima Pahlevan,et al.  Sentinel-2/Landsat-8 product consistency and implications for monitoring aquatic systems , 2019, Remote Sensing of Environment.

[17]  Tarmo Soomere,et al.  Fast shoreline erosion induced by ship wakes in a coastal lagoon: Field evidence and remote sensing analysis , 2017, PloS one.

[18]  Giacomo Grasselli,et al.  Critical Care Utilization for the COVID-19 Outbreak in Lombardy, Italy: Early Experience and Forecast During an Emergency Response. , 2020, JAMA.

[19]  A. Cucco,et al.  Development and validation of a finite element morphological model for shallow water basins , 2008 .

[20]  J. Potter.  Flooding and environmental challenges for Venice and its lagoon: State of knowledge, C. A. Fletcher and T. Spencer (eds.), 2005. Cambridge, Cambridge University Press, 691pp., ISBN 0-521-84046-5, £85, US$ 180 (hardback) , 2006 .

[21]  Alvise Benetazzo,et al.  High-resolution satellite turbidity and sea surface temperature observations of river plume interactions during a significant flood event , 2015 .

[22]  Quinten Vanhellemont,et al.  Adaptation of the dark spectrum fitting atmospheric correction for aquatic applications of the Landsat and Sentinel-2 archives , 2019, Remote Sensing of Environment.

[23]  S. Giove,et al.  Venice and Overtourism: Simulating Sustainable Development Scenarios through a Tourism Carrying Capacity Model , 2020 .

[24]  V. Defendi,et al.  Estimating sediment transport from acoustic measurements in the Venice Lagoon inlets. , 2010 .

[25]  D Cassin,et al.  Can plankton communities be considered as bio-indicators of water quality in the Lagoon of Venice? , 2003, Marine pollution bulletin.

[26]  Matthias Drusch,et al.  Sentinel-2: ESA's Optical High-Resolution Mission for GMES Operational Services , 2012 .

[27]  A. Rinaldo,et al.  Statistical mechanics of wind wave‐induced erosion in shallow tidal basins: Inferences from the Venice Lagoon , 2013 .

[28]  S. Adriano,et al.  Sedimentation rates and erosion processes in the lagoon of Venice , 2005 .

[29]  Vittorio E. Brando,et al.  Mapping turbidity patterns in the Po river prodelta using multi-temporal Landsat 8 imagery , 2017 .

[30]  A. Pugnetti,et al.  Phytoplankton morphological traits in a nutrient-enriched, turbulent Mediterranean microtidal lagoon , 2017 .

[31]  L. Zaggia,et al.  Objectives and structure of the DRAIN project: an extensive study of the delivery from the drainage basin of the Venice Lagoon (Italy). , 2005, Environment international.

[32]  Manuel A. Zambrano-Monserrate,et al.  Indirect effects of COVID-19 on the environment , 2020, Science of The Total Environment.

[33]  L. Zaggia,et al.  Sulphate reduction in the sediment of the Venice canals (Italy). , 2007, Marine pollution bulletin.

[34]  Els Knaeps,et al.  A single algorithm to retrieve turbidity from remotely-sensed data in all coastal and estuarine waters , 2015 .

[35]  Luca Carniello,et al.  Modeling sand-mud transport induced by tidal currents and wind waves in shallow microtidal basins: Application to the Venice Lagoon (Italy) , 2012 .

[36]  Quinten Vanhellemont,et al.  Atmospheric correction of metre-scale optical satellite data for inland and coastal water applications , 2018, Remote Sensing of Environment.