‘May you grow up to be righteousBob Dylan, “Forever Young” (from Planet Waves, 1974)
May you grow up to be true
May you always know the truth
And see the lights surrounding you.’
A recent article in Travel and Leisure highlighted (a good choice of word) the beauty of bioluminescence along the Cape shoreline. It’s a natural phenomenon that is absolutely captivating, regardless of the age or understanding of the viewer. A night time phenomenon, it is seen as a magical illumination of the waves along the shoreline, lighting up the edge of the sea like an aquatic borealis; a ghostly, shimmering pale blue-green light that changes continually with the moving water. It’s almost surreal in its shifting patterns, snaking and glowing along the water’s edge.
What is it? Bioluminescence is the production and emission of light by a living organism; something that to us humans looks to be mysterious beyond understanding. Imagine being able to glow in the dark at will, just by concentrating hard? Evolution decided otherwise, and denied us the enzymes that are required to turn us into two-legged neon signs (perhaps fortunately, on refection.) But in other creatures, mostly aquatic as we will see, it’s actually quite common in nature. To quote the textbook: ‘Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some bioluminescent bacteria, and terrestrial arthropods such as fireflies.’
The beautiful shifting colours we see along the coastline are caused by billions of tiny creatures called ‘dinoflagellates’, single-celled eukaryotes that we would normally classify as algae or plankton. (The name is intriguing, and the original Greek definition is enough to give us a pretty good idea of what these tiny creatures look like under a microscope: from dinos – whirling, and flagellum – whip.) The beautiful night array they create is somewhat tempered by their daytime activities, however: when collecting in abundance they form a visible red colouration in the sea during daytime, known colloquially as red tide, and in this concentration they are poisonous to shell fish and crustaceans. Many has been the time on our shorelines that the carcasses of dead creatures have littered the beaches after a red tide occurrence.
There is, as always, a human influence: the dumping of phosphate into the oceans – runoff from rivers polluted by excess fertilisation – encourages the growth of the paralysing neurotoxin saxitoxin in the dinoflagellates, which is taken up by the shellfish that consume the little creatures by the millions. Which we then catch, cook and enjoy around the braais or restaurant tables, hopefully not losing the use of our limbs in the process. As a result, these little dinos are the subject of much scientific interest; hopefully that interest will grow further understanding about the results of pollution and, as far as the crayfish are concerned, overfishing.
But back to the amazing night time activity of our dinoflagellates. There are a variety of reasons and causes of bioluminescence, but focussing on our coastline dinoflagellate characters, the light is caused by an interaction between an enzyme and a light-emitting compound called luciferin. When reading about the process it is eerily similar to that of nuclear fission… an‘ enzyme-catalysed reaction that involves splitting off a molecular fragment produces an excited intermediate state that emits light upon decaying to its ground state.’ Run for the shelters! Fortunately this is a purely chemical reaction caused by mechanical means (the wave movement of the ocean, or a passing boat, whale or Poseidon), and those of us who have witnessed the glowing light will be intrigued to learn that each bioluminescent flash is only 0.1 seconds long. When one observes the sparkling line of continual luminescence in the water it’s an indication of just how many little creatures there must be to create such a bright long-term effect.
Bioluminescence also occurs in fish, molluscs, jellyfish, comb jellies, crustaceans and cephalopod molluscs, and it’s intriguing to know that at least 76% of deep water species have some form of illumination. It’s pitch black from a few hundred metres beneath the surface of the sea; nature has found a way for creatures residing there to see, communicate, find mates and hunt. Humans may consider themselves apex predators, but we wouldn’t give them much of a chance in that environment. Better take lots of oxygen, a waterproof torch and lots of batteries if you want to find out.
It’s a fascinating topic, yet another of the wonders of life on our planet. A Waterfront Charters sunset cruise is one of your best opportunities to see this phenomenon for yourselves as our luxurious boat takes you gently back to the harbour after witnessing Sol settling over Atlantic horizon. The thrust of the twin hulls through the ocean disturbs the little dinos, and they flash their lights to see what’s going on. A blue-green delight for human eyes – whether you know (or care) what causes it, it amazing to witness. Join us soon for a cruise, and hopefully the dinoflagellates will be there to delight us all.