Environmental compatibility of sand replenishment in the surf zone off the Island of Sylt, 2009-2010

Some 300-400 m³ of sand were dumped per m of coastline. We studied (1) the faunal composition of macrobenthos in the breaker zone along the island of Sylt, and (2) the effects of sand dumping on macrobenthos (a) after 9 months (before - after sampling design), and (b) after four years (comparison of replenished and neighboring non-replenished sites).

The longshore bar consists of coarse sand, but medium and even fine sand can be found where the bar is eroded. These differences in sediment composition cause faunal heterogeneity on a small spatial scale (100s of m) while the fauna is rather homogeneous on larger (km to 10s of km) scales. During sand replenishment, the eroded sites with fine and medium sand were covered with coarse sand.