Posidonia oceanica meadows are considered to be of high importance to the environmental conservation in the Mediterranean Sea, supporting a highly biodiverse habitat and protecting from coastal erosion. In the CIEM wave flume of LIM/UPC (Barcelona, Spain) large scale experiments have been conducted for measuring wave attenuation, transmission and energy dissipation over artificial P. oceanica in intermediate and shallow waters. The effects of submergence ratio hs/D (hs = height of seagrass, D = water depth) and seagrass density (number of stems per squared meter) on the above characteristics are investigated. Mean velocities above and within the simulated P. oceanica are measured and the wave induced flow within the seagrass, which influences processes such as nutrient uptake, waste removal and larval dispersion, is estimated. A meadow with a total length of 10.70 m was constructed using polypropylene artificial plants. Measurements of wave height at different locations along the meadow indicate attenuation of waves for three different submergence ratios (hs/D), two seagrass densities (stems/m2) and various wave conditions. Results are also analysed with regard to the wave induced flow within the field and the effects of hs/D and seagrass density on mean flow characteristics are investigated based on measurements of mean velocities taken within the meadow.

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