Photo: Pacific Underwater: You light up my life! Underwater bioluminescence

A beautiful, and effective, example of bioluminescence in the Midnight Zone off B.C. is the Atolla jellyfish (Credit: NOAA Ocean Explorer via Flickr)

By Kat Middleton, Western Region Science & Policy Intern

On a September night in 2012, I witnessed something spectacular as I pulled a boat to shore on the north end of Vancouver Island. As my hands gripped the sea-soaked rope, drops of water fell from my hands and splashed into the calm of the bay, creating a miniature blue and green galaxy. I wasn't looking at a reflection of the night sky above, and I wasn't hallucinating either — these lights were coming from hundreds of tiny creatures in the water.

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Often seen during the late summer and early fall in B.C.'s coastal waters, these glowing sparks are plankton that produce their own light through a chemical reaction called bioluminescence. Fireflies are the most recognized bioluminescent creatures, but thousands of creatures successfully use bioluminescence, especially in the ocean.

The darkness of the deep ocean (also known as the Midnight Zone) creates an environment where marine creatures can use bioluminescence to communicate, trap food, attract mates and scare away or camouflage themselves from predators.

A beautiful, and effective, example of bioluminescence in the Midnight Zone off B.C. is the Atolla jellyfish, which uses light as a "burglar alarm". If attacked, the Atolla jellyfish emits a circular rotation of blue light, which exposes the attacker to surrounding predators, allowing the jellyfish time to escape. Researchers artificially reproduced this flashy "burglar alarm" as a lure, allowing them to record the first-ever footage of a giant squid.

Scientists have discovered several species of marine creatures that use bioluminescence for camouflage. Many deep-sea predators hunt from below, which allows them to see the silhouettes of prey through the lighter water above them. To camouflage themselves, several species of fish, squid and sharks have adapted bioluminescent bellies. This adaptation, called "counter-illumination", renders these animals almost invisible from below. Some species of squid have developed the ability to control the colour of their bioluminescence from blue to green depending on the temperature of water around them. These squid species move toward the surface at night to feed, where moonlight gives the water a greenish hue. The warmer water temperature near the surface triggers the squid to turn on their green bioluminescence, allowing them to enjoy the plentiful food supply while avoiding the peril of increased visibility for predators hunting from below.

Not all bioluminescent creatures create their own light. Species like the deep dwelling anglerfish — made famous in the animated feature Finding Nemo — rely on a symbiotic relationship with bioluminescent bacteria to produce light. (Symbiotic means two organisms have evolved to work together and both parties benefit from the relationship.) In the case of the anglerfish, the bacteria benefit from the food and safety provided by the fish, while the anglerfish benefits from the light luring prey to its mouth.

The phenomenon of bioluminescence is just one of the beautiful mysteries in our oceans. More than 90 per cent of the deep-sea depths remain unexplored, so we must carefully and consciously conserve marine ecosystems to protect species we have yet to discover. To do this we must implement ecosystem-based management for Canada's oceans, including a network of marine protected areas along our coastline.

September 27, 2013

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1 Comment

Sep 29, 2013
9:13 AM

Thank you for educating us. The bounty of the ocean deserves respect from humans.

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