Environmental risks of large scale cultivation of microalgae: Mitigation of spills

As there are industrial and societal interests in cultivating algae on a large scale, there inevitably will be spills of cultured algae into natural ecosystems. The assessment of environmental risks of such spills is especially hard for cultured, non-native microalgae species due to the “paradox of the plankton”, the paradox that large numbers of species with varying degrees of fitness co-exist in natural ecosystems in an unpredictable, fluctuating species balance. The risk analysis may be more straightforward for special cases, e.g. transgenic or mutated strains of common, indigenous species because their behavior can be compared to their wild types. Risk assessment can be based on presently used Good Industrial Large Scale Practice considerations, particularly the use of mitigating traits that severely decrease fitness. Some desirable introduced genes may have some unfitness in natural ecosystems and can be coupled with antisense or RNAi suppressed genes to mitigate genes that increase fitness. The most stringent mitigation systems are needed especially for non-native species and can utilize deletion mutations (e.g. in carbon capture or nitrate utilization) that allow cultivation only in artificial systems and are lethal to the algae in nature.