Four Centuries of Biological Invasions in Tidal Waters of the Chesapeake Bay Region

Abstract

Biological invasions are prevalent in marine ecosystems throughout the world. Several studies demonstrate that the number and abundance of non-native species have increased dramatically in recent time (Cohen and Carlton 1998; Cranfield et al. 1998; Reise et al. 1999; Ruiz et al. 2000a; Hewitt et al. 2004). Although the impact of many non-native populations remains unexplored, it is also evident that some species have fundamentally altered the structure and function of marine systems (Ruiz et al. 1999; Crooks 2001; Carlton 2001). Most marine invasions are known from protected waters of bays and estuaries, instead of exposed outer coasts (Chap. 33, Preisler et al.). This results at least partly from the concentration of human activities surrounding estuaries, creating many transfer mechanisms (vectors) for the human-aided movement of organisms from other global regions. Most of the world’s trade occurs by shipping among ports, concentrated in bays and estuaries, creating opportunities for species transfers associated with ships’ hulls and ballasted materials (Carlton 1985). In addition, bays are foci for many other activities known to transfer organisms, such as aquaculture, fishing, and outdoor recreation. Estuaries also represent an intersection between marine, freshwater, and terrestrial environments, and potentially can be invaded by organisms from each of these adjacent regions. Although estuaries include a diverse range of habitats and have undergone many anthropogenic changes, both potentially affecting colonization by non-native species, it appears certain that the propagule supply moved among bays is an important driver for the predominance of non-native species in more protected waters. For North America, analyses and syntheses of marine invasions now exist for several estuaries along the Pacific coast (Carlton 1979; Cohen and Carlton 1995; Cohen et al. 1998, 2001; Wasson et al. 2001; Boyd et al. 2002; Wonham and Carlton 2005). European colonization and modern human activities are relatively recent here, with the major expansion in shipping in the 1800s. In contrast, extensive colonization and shipping to eastern North America began in the 1600s, and