University of Central Florida Undergraduate Research Journal - Preventing Introductions to Sustain Healthy Ecosystems: Establish Eradication Protocols for a Popular Aquarium Seaweed
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Introduction

The aquarium industry is worth over $1,000 million worldwide and is a prominent hobby for millions of individuals (Livengood and Chapman 2014). The import value of ornamental fish is over $278 million, with the United States leading the industry as the single largest importer (FAO 1996–2005, Chapman 2000). Additionally, there are approximately 1,539 species of fish, 102 species of corals, and 293 species of invertebrates involved in the aquarium trade (Livengood and Chapman 2014). Although the industry was once dominated by freshwater organisms, marine organisms have recently become more popular due to their rising popularity in pop culture and advances in marine equipment technology.

Accompanying the rise of the marine industry, aquarium release has also increased. Aquarium release is a worldwide concern as a pathway for the introduction of non–native species. Novel species can be introduced intentionally through direct release of organisms or unintentionally through the dumping of live cells in used aquarium water (Calado and Chapman 2006). When novel species enter environments, native species lack evolutionary history and are often unable to form timely defenses. Absence of biotic controls lead to the establishment of invasive species and subsequent habitat degradation (Donnelly 2014).

The invasion of Caulerpa taxifolia in natural ecosystems is one of the best–documented examples of aquarium release (Walters 2009). This green–feathered macroalga stressed the economy and deteriorated the ecosystems off the coasts of South Australia, the Mediterranean, and California (Meinesz et al. 1996, Relini et al. 1998, Williams and Smith 2007). The degradation of the ecosystem caused by C. taxifolia in these locations led the International Union for the Conservation of Nature to place C. taxifolia on the world's 100 worst invasive species list (Lowe et al. 2004). In order to cope with this deadly alga, over $7 million was spent in California to eradicate the invasive populations. The primary method used was chlorine bleach placed under secured black tarps covering the C. taxifolia beds to kill cells and prevent photosynthesis (Anderson 2007).

Knowledge of the invasion of Caulerpa taxifolia influenced more than 50% of individuals attending a national aquarium hobbyist convention to no longer use Caulerpa, but rather instead use Chaetomorpha for their tropical or subtropical reef aquaria, making it the most commonly used algae in home saltwater aquariums (Walters et al. 2011). Chaetomorpha, referred to as spaghetti algae, is a genus consisting of unbranched filamentous green macroalgae. Chaetomorpha has broad environmental tolerances and high nutrient uptake and growth rates (Xu and Lin 2008). Due to the ease of hosting Chaetomorpha and its popularity among hobbyists, it is very likely that some cells may end up in the environment via aquarium dumping or accidental disposal to the waterway.

Many comparative studies between Caulerpa taxifolia and Chaetomorpha have been conducted to assess the safety of using Chaetomorpha as the major macroalgae in marine aquariums. Caulerpa taxifolia can survive and reproduce from fragments as small as 10mm in length (Smith and Walters 1999). Data shows that Chaetomorpha, our genus of interest, can proliferate from a single undamaged cell as small as 0.5mm, suggesting that this macroalgae poses an even greater invasive threat than Caulerpa. In warm environments, such as those present in tropical and subtropical regions, 0.5mm fragments of Chaetomorpha had a 72% survival, 1mm fragments had a 90% survival, and fragments 2mm or longer also had a 90% survival rate (Odom 2012).

Aquarium release of Chaetomorpha may pose an invasive threat even in areas where Chaetomorpha species are native, similar to what occurred during the massive biological invasions of Caulerpa. Meinesz and Boudouresque (1996) suggest that the strong selection pressures exerted on aquarium Caulerpa could have given it a survival advantage over native Caulerpa species. Locally, the introduction of the aquarium Chaetomorpha into the Indian River Lagoon in Florida is a concern due the potential for genetic recombination and speciation during years of isolation in the aquarium industry. According to the Smithsonian Marine Station at Fort Pierce, there are five species of the Chaetomorpha genus documented as native to the Indian River Lagoon, including Chaetomorpha aerea, Chaetomorpha brachygona, Chaetomorpha gracilis, Chaetomorpha linum, and Chaetomorpha minima (2014). Chaetomorpha suppliers continually pull from a limited gene pool and years of genetic isolation may create a different population that could act as a thriving invasive species in the Indian River Lagoon. Furthermore, Florida is greatly affected by invasive species due to island development, tropical climate, and high seasonal rainfall (Masterson 2007).

Many scientists have recognized Chaetomorpha's threat to the environment and have tested effective eradiation measures. In summary, the exposure time and concentration of tested chemicals to cause growth reduction or full mortality of Chaetomorpha is significantly higher than previously studied in C. taxifolia strands (Odom and Walters 2014). Moreover, chlorine bleach is not effective in inducing full mortality among the macroalgae, as was the case for California's chemical eradication of C. taxifolia (Williams and Schroeder 2004). Application of fluridone and copper sulfate is also futile to induce full mortality (Odom and Walters 2014). Acetic acid is one of the only acids tested to consistently reduce survivorship and growth, documented to cause full mortality at 2% concentration for 4–minutes exposure time and 4% concentration acetic acid for 1 minute (Odom and Walters 2014). However, no other dose–responses have been tested.

With the knowledge that acetic acid was the most effective tested chemical at causing consistent mortality, the goal of this project was two-fold. The first goal was to determine the minimum concentration and exposure time necessary for full mortality by testing a wide range of doses and responses. The second goal was to test if store-bought acetic acid (vinegar) could replace experiment–grade acetic acid for household hobbyist use.

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