Blood berries, called Haematococcus pluvialis, are unicellular green algae that have the ability to enter a resting state where they accumulate a red ketocarotenoid pigment called astaxanthin. This pigment is even used to commercially colour the flesh of salmon.

When blood berries are under stressful conditions such as intense light, high salinity, nitrogen and phosphate deprivation, they accumulate antioxidant carotenoids which are believed to protect the cell from photooxidative damages. Astaxanthin acts as sunscreen and partially blocks blue light from penetrating the cell and from damaging the precious chloroplasts!