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Biological Invasions: Consequences for Parasites, Pathogens, Emerging Diseases, and Fisheries in the Marine Environment.

Gregory M. Ruiz¹ and Fred C. Dobbs²

¹Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, MD 21037 USA.
²Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, 4600 Elkhorn Avenue, Norfolk, VA 23529 USA;
Email: ruizg@si.edu

Biological invasions are a major force in aquatic (including freshwater and marine) ecosystems, driving significant ecological changes and impacting many dimensions of society. Effects of invasions on fisheries species have received considerable attention, demonstrating simultaneously ecological and economic consequences. Most analyses of invasions and invasion impacts have focused on relatively large, conspicuous non-native biota, indicating a size-based taxonomic bias in detection and understanding. Despite this pattern, several attributes of microorganisms (e.g., protists, bacteria, and viruses) increase the likelihood of invasion relative to larger organisms. First, the magnitude of organism transfer (or propagule supply) increases with decreasing size, and invasion success (establishment) has a strong density-dependence. Second, many microorganisms can reproduce asexually, which should serve to minimize the inoculant size required for establishment. Third, many microorganisms have broad environmental tolerances, increasing the geographic range and seasonal window available for colonization. Fourth, the life-history of microorganisms often includes stages (e.g., resting stages or cysts) that can further extend environmental tolerance by avoiding temporally unsuitable conditions. We predict that invasions by microorganisms are widespread, occurring largely without detection, and may contribute to the observed increase in emerging diseases in marine ecosystems.

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