This member of the Volvocales is usually encountered by people who have the good sense to install birdbaths in their gardens. Very often the first indication that something strange is happening is that the water begins to change to an orange-red colour. If you're lucky enough to have a microscope at hand a strange sight awaits you. The culprit for this unusual coloration is a micro-organism called Haematococcus pluvialis. The red colour is due to the pigment called astaxanthin, which possibly protects the organism from the harsh sunlight, especially the ultraviolet rays from the Sun...
26 August 2011
Why the birdbath turns red