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Alternatives to Release: Efficient Methods for Disposal of Excess or Unwanted Aquarium Macroalgae in the Genus Chaetomorpha

  • Rachel L. Odom (a1), Joshua A. Solomon (a1) and Linda J. Walters (a1)

Aquarium release is a vector for introducing nonnative species that threatens the ecological integrity of aquatic systems. Following coastal invasions by released aquarium strains of Caulerpa taxifolia, aquarists began using the macroalgal genus Chaetomorpha. Use of Chaetomorpha now exceeds 50% of U.S. aquarium hobbyists we surveyed. Aquarium strains of this macroalgal genus possess broad environmental tolerances, demonstrate high nutrient uptake and growth rates, and reproduce by fragmentation. Although these characteristics make Chaetomorpha a desirable aquarium inhabitant, they may also promote invasive tendencies if the alga is introduced into a natural ecosystem. We sought to proactively mitigate this potential invasion risk by testing algal disposal techniques that serve as responsible alternatives to releasing viable individuals. We tested methods used by aquarium hobbyists—boiling, microwaving, freezing, desiccation, and exposure to freshwater. We determined the minimum durations that these techniques must be used in order to induce mortality in three aquarium purchases of Chaetomorpha. We found that boiling for at least 1 min, microwaving for at least 15 s, or freezing for at least 24 h were sufficient to induce 100% mortality in 1-cm-long fragments and clumps up to 1.5 g. Desiccation required more than 24 h when exposed to air and 6 d for samples kept in closed containers. Freshwater exposure was effective at 6 d. These results indicate that disposal of excess or unwanted Chaetomorpha via garbage (if destined for a landfill) or indoor plumbing (e.g., sinks and toilets) represent safe alternatives to release. Disposal of algal tissue, shipping water, or tank water containing small algal fragments down stormwater drains, however, could introduce this hardy species into favorable conditions that could result in detrimental biological invasions.

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