Spirulina is a cyanobacterium (blue-green algae) increasingly consumed as a protein supplement, raising minimal welfare concerns but relevant production considerations.
Spirulina production has among the lowest animal welfare impacts of any protein source, as it involves cultivating a photosynthetic microorganism rather than raising animals. The primary welfare considerations are indirect: spirulina production displaces animal protein consumption, reducing demand for higher-welfare-impact foods. Quality concerns in some spirulina production (contamination with microcystins from other algae species) are primarily human health rather than animal welfare issues. Supporting the spirulina industry is welfare-positive primarily through its displacement of animal agriculture.