Non-indigenous invasive bivalves as ecosystem engineers

Several non-indigenous bivalve species have been colonising aquatic ecosystems worldwide, in some cases with great ecological and economic impacts. In this paper, we focus on the ecosystem engineering attributes of non-indigenous invasive bivalves (i.e., the capacities of these organisms to directly or indirectly affect the availability of resources to other species by physically modifying the environment). By reviewing the ecology of several invasive bivalves we identify a variety of mechanisms via which they modify, maintain and/or create habitats. Given the usually high densities and broad spatial distributions of such bivalves, their engineering activities can significantly alter ecosystem structure and functioning (e.g., changes in sediment chemistry, grain size, and organic matter content via bioturbation, increased light penetration into the water column due to filter feeding, changes in near bed flows and shear stress due to the presence of shells, provision of colonisable substrate and refuges by shells). In addition, changes in ecosystem structure and functioning due to engineering by invasive bivalves often have very large economic impacts. Given the worldwide spread of non-indigenous bivalves and the varied ways in which they physically modify habitats, their engineering effects should receive more serious consideration in restoration and management initiatives.