I remember the first time that I saw the glowing waters of the Southern Gulf Islands. My friends convinced me to go swimming at Campbell Bay late one evening, claiming that the bioluminescent waters would amaze me! I must say, the experience was pure magic. Diving into the summer warmed waters, watching as every droplet sparkled and shone as if the whole ocean were on blue fire. Even after seeing the bioluminescence every year on Mayne Island, it is still hard to explain the beauty of the event; one simply must see if for themselves to understand.

Bioluminescent dinoflagellates light up when disturbed. Photo: slworking2

What is Glowing in the Dark?

Ocean bioluminescence results from a chemical reaction that produces light energy within a living organism. For a reaction to occur, oxygen mixes with a molecule called Luciferin to produce light. The word Luciferin comes from the Latin word lucifer, meaning “light-bearer.” Animals can control when to light up, depending on their need for a mate, a meal, or a quick escape. The light produced this way is considered a cold light, which means that only a small percentage of the light contains heat, unlike the sun’s rays or the light produced by a fire.

The ocean bioluminescence that we see in the waters around Mayne Island are created by dinoflagellates: tiny, single-celled plankton. There are thousands of species of dinoflagellates throughout the oceans of the world, and most of them reproduce asexually. It is assumed that dinoflagellates light up when disturbed to intimidate or escape predators. Marine Biologist Edith Widder calls the phenomenon a “bioluminescent burglar alarm.”

Aside from dinoflagellates, there are many, many bioluminescent marine creatures glowing and lighting up our oceans; scientists have identified over 1,500 species of fish as well as jellyfish, worms, sea stars and sharks.

Microscopic dinoflagellates, magnified. Photo: fickleandfreckled

Where and When to See Bioluminescence

Ocean bioluminescence can be experienced across the world, from the magical waters of Mosquito Bay, Puerto Rico to the pristine waves of Jervis Bay, Australia. The Southern Gulf Islands boast a spectacular display of sparkling waters with some recommended viewing areas being Campbell Bay on Mayne Island, Burgoyne Bay on Salt Spring Island, and Port Browning Harbor on Pender Island. Many folks agree that the best time to see the ocean sparkle is during the hotter months of summer, particularly the days surrounding the new moon when the night sky is darkest.

Cresting wave illuminated by ocean bioluminescence. Photo: Kevin Baird

Relevance in the Food Chain

Most dinoflagellates are photosynthetic, meaning they capture energy from the sun. Many species of dinoflagellates are mixotrophic: they use a combination of photosynthesis and ingesting live prey to acquire energy. Most dinoflagellates have two paddle-like flagella, one to rotate and one to swim forward. This allows them to secure the best position to photosynthesize. As microscopic, single-celled organisms, dinoflagellates are at the bottom of the food chain, providing food for a vast array of marine creatures. Some dinoflagellates are symbiotic or parasitic, living inside hosts such as corals, flatworms and jellyfish.

Red Tide: A Different Dinoflagellate

A rapid accumulation of certain dinoflagellates can cause a harmful algal bloom, also known as a red tide. Red tides are naturally occurring, but can be more common and severe in warm and polluted coastal waters. A red tide occurs when the population of specific dinoflagellates increases exponentially and appears to discolour the water due to the reddish-brown coloring of the dinoflagellates. Certain conditions can cause these population explosions such as the right combination of salinity, nutrients, and temperature.

Red tides can represent a serious threat to coastal ecosystems. Human activities on land can result in red tides when excessive fertilizers, sewage, and soil runoff enter the ocean. These nutrients cause explosive growth of microscopic species of dinoflagellates, some of which carry toxins that are harmful or even lethal to other organisms. In some cases, shellfish or smaller fish who ingest the toxic dinoflagellates are not harmed. However, they accumulate the toxin in their tissues, concentrating it and potentially causing harm to organisms higher up the food chain such as us humans.

While a red tide can be catastrophic in terms of damages to marine ecosystems and danger to humans and terrestrial animals, it is important to note that many blooms of dinoflagellates are not harmful. Harmful algal blooms are closely monitored by Fisheries and Oceans Canada through satellite imagery, and unless advised most ocean bioluminescence does not suggest a harmful algal bloom.

Red tide can be caused by dinoflagellates, but not all dinoflagellate blooms are toxic. Photo: Alejandro Díaz

Small Creatures, Big Impacts

The oceans of this world are an amazing, intricate place with abundant and complicated ecosystems. Before researching for this article, I had no idea that tiny, microscopic phytoplankton could spark and glow like magic in the waters of my Gulf Island home. I also had no idea that dinoflagellates caused the algal blooms I had been warned about. Who knew such a small organism could play such a big role? These simple, base-of-the-food chain organisms have amazed, enraptured, and enthralled me. They may be small, but the impression that they have left is lasting and mighty.

Further Reading

Fisheries and Oceans Canada – Shellfish Harvesting and Safety


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