In the tidal inlet of the back barrier area of Spiekeroog Island (Southern North Sea), nutrient concentrations (silica, phosphate, and nitrite plus nitrate) were determined hourly by an autonomously analysing system on a permanently installed time-series station from April 2006 to December 2008. Based on the high frequency of analyses we studied nutrient dynamics on annual, seasonal, and tidal time scales. By comparing the nutrient input to the tidal flat area via freshwater through a flood-gate and pore water discharge from tidal flat sediments, we conclude that nutrients are primarily supplied to the water column by pore water advection, while the freshwater contribution is negligible. To assess the annual nutrient contribution of our study area to the German Bight, we used a numerical Euler-Lagrangian model (EcoTiM) to calculate annual budgets of silica and phosphate. The model results indicate that the back barrier area of Spiekeroog Island exports inorganic silica (128 * 10 6 mol a -1 ), phosphate (3 * 10 6 mol a -1 ), and nitrite plus nitrate (29 * 10 6 mol a -1 ) to the North Sea. Extrapolation of these data to the entire Wadden Sea along the southern North Sea reveals that the back barrier areas export silica and phosphate in the same order of magnitude and nitrite plus nitrate one order of magnitude lower than the combined rivers Elbe, Weser, and Ems.

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For three different wind propulsion technologies, the energy saving potential of sea going cargo vessels are discussed: a kite, a Flettner rotor and a Dynarig-sail. The energy saving potential can be increased significantly if the route can be optimized when using a wind assisted ship propulsion. The increase of travelling time due to a route adoption is within the frame of the commonly accepted uncertainty in supply chains and can be limited or adjusted in the route optimization software as a parameter. The calculated saving potential depends on several parameters: the considered wind propulsion system, the route, the kind of ship (bulker, multipurpose carrier, tanker), as well as the ship speed and the weather. The cost-effectiveness of the installation of a wind propulsion system strongly depends on the fuel price, the ship speed and the international policy concerning the ship emissions.

No abstract

For three different wind propulsion technologies, the energy saving potential of sea going cargo vessels are discussed: a kite, a Flettner rotor and a Dynarig-sail. The energy saving potential can be increased significantly if the route can be optimized when using a wind assisted ship propulsion. The increase of travelling time due to a route adoption is within the frame of the commonly accepted uncertainty in supply chains and can be limited or adjusted in the route optimization software as a parameter. The calculated saving potential depends on several parameters: the considered wind propulsion system, the route, the kind of ship (bulker, multipurpose carrier, tanker), as well as the ship speed and the weather. The cost-effectiveness of the installation of a wind propulsion system strongly depends on the fuel price, the ship speed and the international policy concerning the ship emissions.