Globalization under water: Alien species in the Wadden Sea World Heritage. Recent investigations reveal an increasing number of non-native species in the Wadden Sea which profit from warmer water temperatures caused by global change. These exotic species achieve highest occurrence and densities in shallow waters near the low tide water level. In this tidal zone, a highly diverse species community of algae and invertebrates became established and will continue to alter in composition. This leads to enhanced complexity of biogenic habitats and to a prevalence of filter feeding organisms. Thus, we observe a fundamental change of the whole Wadden Sea ecosystem which is without return. © 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.