by Stephen Luntz
Photo credit: Will Ho. Wave action on this Maldive beach turns on the lights of these bioluminescent bacteria
Let’s just take a moment to breathe in the astonishing beauty of the planet we live on. Example for the day: beaches where waves, or even footprints reveal a bioluminescent glow.
A beach Maldives achieved fame earlier this year when photos of bioluminescent wonder came to light (see above). Fortunately, the phenomena is not limited to a single location. Astrophotographer Phil Hart recorded a period when Australia’s Gippsland Lakes lit up as though the waters were as rich with stars as the sky.
Many creatures in the depths of the oceans use bioluminescence to find mates, or to attract prey. The most familiar example, particularly for North Americans, is fireflies (lampyridae). In all cases the light is produced using a chemical reaction. Species use different forms of luciferin, a class of chemicals that are unstable when exposed to oxygen, as an energy store that releases light when exposed to air. An enzyme luciferase acts as a catalyst to ensure the reaction happens fast enough to produce a noticeable glow.
The reactions produce light concentrated in a narrow band of wavelengths, which is why a particular species of insect or bacteria will produce a certain color. By not wasting energy producing much heat or ultraviolet radiation life forms can produce enough light to get noticed without busting their energy budget. A side effect is that the light has a strong color – blue, green or yellow depending on the exact chemicals used – which makes it even more beautiful to our eyes than white would be.
Oceanic bacteria of course have no need to find mates. It is thought they use their glow as a form of self-defense. While the light makes them more visible to creatures that might eat them, it also attracts predators higher up the food-chain, providing the bacteria with a level of protection. Rather than waste their energy, the bacteria only glow when they sense something that may consume them, but this can misfire and be triggered by waves or footprints.
Areas of bioluminescent bacteria can be so large they are visible from space. Usually however, they are not as bright as we see in the images here.
Sadly for time-poor individuals planning their next holiday, events like the ones captured here can’t be reliably predicted. As Hart explains, the Gippsland event resulted from huge fires followed by major floods in the lakes’ catchment area. The nutrients washed down as a result sparked a huge outbreak of a one species of microorganism, which eventually became a feast for another, Noctiluca scintillans, which as the name suggests has a beautiful glow. As an added bonus, while many related species are toxic, waters filled with N scintillans is safe for people to play in.