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Venice Lagoon case study: The Problem

Venice Lagoon case study: The Problem. 1960s and 1970s Uncontrolled discharge of nutrients 1980s Hypereutrophic conditions Macroalgal density = 20 kg FW m-² loss of SAV beds and change in species abundance Severe anoxia in parts of the lagoon. Dissolved Oxygen 2004-2005.

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Venice Lagoon case study: The Problem

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  1. Venice Lagoon case study: The Problem 1960s and 1970s Uncontrolled discharge of nutrients 1980s Hypereutrophic conditions Macroalgal density = 20 kg FW m-² loss of SAV beds and change in species abundance Severe anoxia in parts of the lagoon

  2. Dissolved Oxygen 2004-2005 SAV distribution 2002 Venice Lagoon case study: The Solution • 1980s • Wastewater treatment plants (WWTP) built • P banned from detergents • 1990s to present • Decrease in nutrient loads and P concentrations • Macroalgae density now 0.5 FW m-² • SAV beds returning - since 1992: • Zostera marina increased (2.6 – 22 km²) • but Nanozostera noltii decreased (14 – 0.7 km²) • No anoxia – DO at 40% saturation, adequate for aquatic life • Future • New WWTP and phytodepuration plants planned • Industrial zone effluents closely monitored • Continued improvement expected

  3. Venice LagoonASSETS Application (early 2000s) ASSETS: HIGH Indices Overall Human Influence (OHI) ASSETS: 3 Overall Eutrophic Condition (OEC) ASSETS: 5 Determination of Future Outlook (DFO) ASSETS: 4 Methods Susceptibility Nutrient inputs Primary Secondary Future nutrient pressures Index Moderate LOW Improve Low Parameters Rating Expression Dilution potential Low High susceptibility Flushing potential Low High Chlorophyll a Low Low Macroalgae Low Dissolved Oxygen Low Submerged Aquatic Low Vegetation Low Nuisance and Toxic Low Blooms Future nutrient pressures decrease http://www.eutro.org/

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