allow fish circulation despite deviation in the marsh). Calculation of ecological gains using HEA gave us 0.079 DSAYs and 0.158 DSAYs for performances of 2 and 4 kg per day per hectare respectively. Objective for valuation Metrics Determination of baseline DSAYs Nitrate mitigation Purification performances of 2 kg per day Objective of 50 tons per year 0,079 Nitrate mitigation Purification performances of 4 kg per day Objective of 50 tons per year 0,158 Table 5 - Application of HEA to measure the environmental gains in the Kervigen marsh The strategy of restoration fixes an objective of reduction of 50 tons of nitrate per year, this can be considered as a deficit of ecological services: if nothing is done 100% of services will be lost, corresponding to 18.41 DSAYs between 2012 and 2037. Considering the gains associated to the Kervigen marsh rehabilitation we can propose discussion on the different strategies for restoration of marshes (Table 4). Using HEA we can determine the need of restoration to reach 50 tons of nitrate reduction. We can see that changing the time limit for the objective will change the total surface of project, because of the application of a discount rate that gives preference for services produced in 2012, rather than later. Strategy for marsh restoration Surface to restore per year Total surface to restore Objective in 2012 234 ha 234 ha Objective in 2015 64 ha 254 ha Objective in 2020 33 ha 294 ha Table 6 - Dimensioning restoration plan according to different strategy scenario for a selected performance of 2 kg.day-1.ha-1 Environmental measures of Port 2000 The Seine estuary refers to the part of the river that is subject to tidal influence. It is a densely populated region and home to a variety of economic activities. The estuary is characterized by the presence of a high biological diversity (birds, fish, etc.) and included in the Natura 2000 network. It is also protected by the existence of the Nature Reserve of the Seine Estuary. Because of the construction of Port 2000, the Le Havre harbor had to set up two types of environmental measures to offset impacts on local biodiversity: compensatory measures and accompanying measures. Compensatory measures that focused on the creation of a resting place on dune - a resting area of 45 ha consisting of a basin subject to tidal influence and a large dry area - and an islet resting place - an islet of 5 hectares at low tide which is reduced to 1.5 ha and three smaller
Libellule® zone Environmental measures of Port 2000 Kervigen marsh Vurpillères stream Mudflats rehabilitation Repositories Objective for valuation Depending on the targeted market Creation of 100 ha of mudflat Ecological neutrality of Port 2000 on the shorebirds in the estuary Reduction of 50 kg nitrate per year through restoration of marshes Ecological restoration of the site to its itinial state Metrics e.g. Dissolved oxygen Surface of mudflats Abundance of shorebirds in the estuary Absorbed nitrate Species richness Initial level State of metric before works Null Number of shorebirds before impact Absorbed nitrate without the marsh Number of species before restoration Intensity of restoration Evolution of metrics during time Surface of mudflats observed in 2008 and 2012, we assume linear growth between observations Variation of number of birds from 2005 and return to the baseline in 2010. Purification performance associated to the latest measures in 2008. Number of observed species in 1993, 1998, 2002 and 2007, we assume linear growth between observations Hyptohsesis on the final level Management plan maintains level of service to its 2011 state. Site is stabilised in 2012. Return to the baseline in 2010. Management plan maintains performance to its 2008 state. In 2007, level of service is back to its initial level. Reference state Dissolved oxygen in the Or lagoon Objective of mudflat creation (100 ha) Number of birds in the estuary in 1997 Nitrate reduction objective (50 tons per year) Species richness in 2007 Reference date Beginning of works (2007) Beginning of works (2005) Beginning of impact (1997) Beginning of project (2010) Start of project (1997) DSAYs 1.26 9.12 0.131 0.079 5.79 Table 9 - Synthesis of the application of HEA for valuation of actions of restoration of aquatic ecosystems