During an algal bloom the species produce a toxic chemical substance which is harmful to animals that feed on the algae that causes a tint in the water because of the photosynthetic pigments is known as a red tide a red tide may or may not be harmful . Nonetheless algal bloom can produce both beneficial and harmful cycles.
It is beneficial because it can provide organic compounds needed by higher organisms, for this reason productivity increases because there's more algae in the water which means that more carbon dioxide is used from the atmosphere and that more oxygen is being released into the atmosphere which is needed and necessary for many living things
