genetic markers of toxin production. Methods to distinguish some toxin-producing strains from other strains are available. For example, an oligonucleotide probe can distinguish hepatotoxic from neurotoxic Anabaena and these strains from Nostoc spp. (Rouhiainen et al., 1995). Information supporting genetic markers of toxin production is increasingly available, for example, a PCR-based test to assess the potential for microcystin occurrence (Nonneman and Zimba, 2002). However, these tests cannot identify unknown toxins, and they can give false-positive results where toxins are not expressed, for example, where multigene families are needed for arrangement (Zimba et al., 2010).
Directly measuring all pathogens in algal culture media is not generally practical. Indicator species are often microorganisms that are nonpathogenic, abundant, and associated with the presence of a suite of pathogens (EPA, 2011b). For example, densities of fecal coliform and Salmonella can be used as indicators for assessing the efficiency of wastewater treatment (40 CFR 136). These can be measured via culture methods or through quantitative polymerase chain reaction tests for fecal indicator bacteria that provide sameday information (Dorevitch et al., 2011). The abundance of fecal indicator bacteria can be related to disparate pathogens, such as protozoa (Dorevitch et al., 2011). However, typical indicator organisms are not useful in all media or for all pathogens. For example, Pepper et al. (2010) found that indicator organisms in Class B biosolids were not correlated with the numbers of pathogenic organisms. Criteria for selecting non-pathogen indicator organisms of pathogens in waters have been summarized by EPA (2011b), based on information in Gerba (2009) and NRC (2004). These include attributes of organisms and testing methods. Analytical methods for detecting low densities of pathogens have not been sufficiently developed and tested to be recommended (EPA, 2011b). Any potential indicators would have to be tested in algal ponds or photobioreactors for potential relationships with pathogen levels. Attributes of non-pathogen indicator organisms of pathogens in waters and attributes of methods for detecting pathogen indicator organisms are described in an EPA report Problem Formulation for Human Health Risk Assessment of Pathogens in Land-applied Biosolids (EPA, 2011b).
5.11.1 Potential Environmental, Health, and Social Acceptability Effects
Health effects from and social acceptability of algal biofuels could be affected if open ponds are poorly managed and provide habitats for mosquito larvae. Photobioreactors and raceways would not represent mosquito habitat unless there is substantial leakage of culture fluid, and puddles are formed. Mosquitoes lay their eggs opportunistically in standing water, which can vary from large lakes to small puddles or buckets. The full area of algae cultivation ponds would not be optimal habitat because of the required stirring and agitation for adequate mixing of nutrients and light exposure. Females of most mosquito species only infrequently lay eggs in flowing or agitated water (Lothrop and Mulla, 1996; Mogi and Motomura, 1996). Moreover, waters that are in motion can interfere with the surface tension required for mosquitoes’ respiratory siphons to function (Schober, 1966). However, any relatively still edges of open ponds (analogous to stream banks and floodplains along moving streams) and outlying puddles or open-water storage vessels would be suitable for the growth of mosquito larvae. Because algae constitute food for mosquito larvae, the high nutrient and carbon content of algal cultivation systems (when and where the water is relatively still) can be prime habitat (Rydzanicz and Lone, 2003). The turbidity