Landscape design also may be considered to limit any potential impacts of releases of algae from pond systems. Placing systems well away from waterways and wetlands where pond algae may thrive could reduce or minimize the likelihood of blooms of released species. When considering the factors that affect the probability of release and the abundance of released organisms above, then mitigation measures might include shields from wind and mechanisms to discourage vectors.

5.6.6 Sustainability Indicators

Indicators of sustainable ecological communities include metrics of aquatic diversity and invasiveness of algae. One category of such metrics would be diagnostic traits for invasiveness. Qualitative metrics that are related to invasiveness, but not necessarily diagnostic, include:

•  Fast growth in natural environments.

•  Wide habitat tolerances, for example, tolerances for temperature, light, and nutrients.

•  Pest and herbivore resistance.

•  Aggressive competition for resources, for example, light, nutrients, or space.

More direct metrics of aquatic biodiversity that relate to the sustainability of biofuels are recommended by McBride et al. (2011) and are pertinent here:

•  Presence of taxa of special concern. These may include rare fish, aquatic invertebrates, or macrophytes.

•  Habitat area of taxa of special concern, which for aquatic organisms might translate to stream reach length for taxa of concern.

Additional sustainability indicators for aquatic biodiversity might include the types of metrics found in recovery plans for species protected under the Endangered Species Act (Table 5-9).

TABLE 5-9 Recovery Goals for Endangered and Threatened Species in U.S. Fish and Wildlife Service Recovery Plans

Type of Recovery Goal

Metric for Recovery


Total population size
Number of subpopulations
Number of individuals in each subpopulation
Trends in total population size
Trends in number of subpopulations
Trends in number of individuals in each subpopulation


Age structure of population
Productivity and net recruitment


Total range (presence/absence)
Quality of habitat
Quantity of habitat

SOURCE: Adapted from Efroymson et al. (2009), whose sources were Campbell et al. (2002) and Gerber and Hatch (2002). Reprinted with permission from Elsevier.

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