Screening of natural product biocides for control of non-indigenous species

Several benzo-, naphtho- and anthraquinones were tested for their efficacy as biocides in controlling aquatic nuisance species in ships' ballast water. A requirement of this application was broad spectrum aquatic toxicity, coupled with a relatively rapid rate of degradation, in order to comply with coastal discharge requirements. Compounds were screened using a suite of toxicity bioassays designed to establish their relative toxicity to an array of planktonic organisms including larval bivalves Dreissena and Crassostrea, various developmental stages of the estuarine copepod Eurytemora affinis, brine shrimp larvae (Artemia salina), the freshwater invasive water flea Bythotrephes, larval sheepshead minnows (Cyprinodon variegates) and two unicellular algal genera Isochrysis and Neochloris.. The majority of the data were recorded as the lowest concentration of the test compound resulting in complete mortality or inactivation of test organisms (LC (100(99)). The naphthoquinones juglone, plumbagin, menadione and naphthazarin showed the highest toxicity to the broadest range of organisms, often at levels much less than 1 mg l(-1), and most of the attention was focused on this group. While plumbagin and juglone appeared overall to be the most toxic compounds, it was concluded that menadione was probably the most cost-effective candidate compound for shipboard use for controlling invasive species in ballast water, particularly in view of the large volumes of water that would require treatment.