Digging for and grabbing the answers: novel whole-ecosystem approach quantifies damage and reveals mechanisms of invader-driven habitat destruction

摘要

The feature article by Garbary et al. (2013), reporting damage of eelgrass beds (Zostera marina) due to digging and foraging activities of invasive European green crabs (Car-cinus maenas), reminds me of some own recent experiences of this phenomenon, achieved within a mesocosm experiment at Solbergstrand in southeastern Norway in 2012 (Christie and Kraufvelin unpubl., see Kraufvelin et al. 2010 for a description of the mesocosms). Focusing on combined effects of nutrient enrichment and mesopredator release (due to overfishing of top predators) on rocky shore ecosystems, we also included sediment trays with eelgrass only to discover that numerous of our "gardened" eelgrass individuals were effectively eradicated by green crabs during the course of the experiment (within a few months). In comparison with the scenario described by Garbary et al. (2013), however, the damage in the mesocosms was marginal, despite causing complete disappearance from some trays and some mesocosm treatments, because not only it took place in artificial ecosystems but also happened in the native region of the crab (Fig. 1).