that use terrestrial crops as feedstock (Beeman, 2007; Smith, 2008; EPA, 2009b; Buntjer, 2010; Meersman, 2010; O’Sullivan, 2010). Regulation and compliance assurance would address concerns about release of harvest water.
The potential for accidental release of cultivation water exists; for example, clay or plastic liners could be breached through normal weathering or from extreme weather events, some of which are predictable. High precipitation or winds could lead to overtopping of ponds or above-grade raceways. In those cases, the entire contents of algal cultures could be lost to surface runoff and leaching to surface water or groundwater. Siting in areas prone to tornadoes, hurricanes, or earthquakes would increase the likelihood of accidental releases. However, producers are likely to take preventive measures when extreme weather events are forecasted, and they would put effort into preventing accidental releases of cultivation water because such events could adversely affect their profit margin.
22.214.171.124 Potential Environmental Effects
Large-scale algae cultivation requires the provision of large quantities of nutrients, especially nitrogen and phosphorus, to ensure high yield (see section Nutrients in Chapter 4). Even where nitrogen and phosphorus are not in oversupply, the total nutrient concentrations in algal biomass will be high. Although accidental release of cultivation water into surface water and soil is unlikely, such an event could lead to eutrophication of downstream freshwater and marine ecosystems, depending on the proximity of algal ponds to surface and groundwater sources.
Eutrophication occurs when a body of water receives high concentrations of inorganic nutrients, particularly nitrogen and phosphorus, stimulating algal growth and resulting in excessive algal biomass. As the algae die off and decompose, high levels of organic matter and the decomposition processes deplete oxygen in the water and result in anoxic conditions (Smith, 2003; Breitburg et al., 2009; Rabalais et al., 2009; Smith and Schindler, 2009). In some cases, eutrophication-induced changes could be difficult or impossible to reverse if alternative stable states can occur in the affected ecosystem (Scheffer et al., 2001; Carpenter, 2005).
Eutrophication effects have been well studied, and they depend on the nutrient loadings to the receiving waters and the volume and residence time of water of these systems (Smith et al., 1999; Smith, 2003). High nutrient loading could lead to anoxia in the deep cool portion of lakes or in hypoxia in the receiving water bodies. Potential biotic effects of eutrophication include changes in algal density and in the structure and biomass of the broader ecological community (Scheffer et al., 1997; Reynolds et al., 2002; Smayda and Reynolds, 2003). Fish yield is affected by phytoplankton1 biomass and by the nutrient ratios in the edibility of phytoplankton (Oglesby, 1977; Bachmann et al., 1996).
Nutrient levels play a key role in determining the productivity and structure of the primary producing community in estuaries and coastal marine waters (Deegan et al., 2002; Smith, 2006) and by extension, the productivity and structure of higher trophic levels. Nutrient-enriched shallow marine systems tend to have a reduced seagrass community (Burkholder et al., 1992; Hauxwell et al., 2003) because elevated nitrogen concentrations and loadings adversely affect seagrass (Efroymson et al., 2007 and references cited therein).
1 A collection of microscopic photosynthetic organisms that float or drift in fresh water or sea water.