Tag Archives: Light

Light and Color Below the Surface

Have you ever gone diving and noticed that colors above the surface may look very different than colors below? This is because light and color are very different underwater. Water is very good at absorbing light, and to understand this a little bit better, let’s talk about good ol’ Roy G. Biv.


(Light on the surface appears very different than light below.)

Roy G. Biv (an acronym for the color spectrum) stands for the colors red, orange, yellow, green, blue, indigo, and violet. These colors are in order from lowest to highest energy. Sunlight contains all of the colors of our visible color spectrum and these colors combined together create white light. As you travel from the surface to deeper waters, the amount of light changes and decreases with depth.

light wave

(Red light has the longest wavelength as shown above.)

Red light has the longest wavelength and therefore has the least amount of energy in the color spectrum. Wavelength decreases as energy increases as you move from red to violet light across the color spectrum. Blue light however penetrates the water the best. This is why the ocean can appear in many different shades of blue. Unlike blue light, red light becomes quickly filtered from water as the depth increases. At around 300 feet, no visible light can penetrate the water at all!

Let’s take an apple for example. At the surface an apple appears red. It appears red because it is reflecting that red light from the sun. When taking this apple down to depth at around 70 feet however, it lacks the red coloration and appears greyish. This is because the deeper you go, there is less and less red light to reflect off the apple. This is an amazing adaptation for deep-sea creatures to have. Deep-sea creatures that are red will appear less visible to prey.

light brooke

(Left: Apple appears brownish at depth.)










Written By: Brooke Fox

Biofluorescence: Sea Creatures Glow with Invisible Ink

You’ve probably heard of bioluminescence, where some ocean animals make their own light to communicate, attract prey, or distract predators. But did you know that much of the ocean world is already glowing in a way that’s invisible to your naked eye? Many corals, more than than 180 species of fish, some sharks, at least three types of eels, and one critically endangered sea turtle, the Hawksbill, would actually display neon colors if you were to shine a black light or UV light on them, in a phenomenon called biofluorescence.


That’s right: When stimulated by UV light, these creatures produce all sorts of flashy colors, from reds to greens to eerie iridescent purples. Unlike bioluminescence, these types of light signatures depend on a light source, and are typically invisible to the human eye. That’s why, until as recently as 2014, researchers didn’t know that other marine species besides coral were capable of this type of biofluorescence. In fact, it wasn’t until an eel accidentally “photo-bombed” a video shoot of coral under a UV light (below) that marine biologists began to investigate this capability in other animals!

Biofluorescence 2

Why do they do it? 

Scientists don’t know why creatures biofluoresce, but some hypothesize that it may be a form of complex communication with only other creatures who may see these unique UV emissions. For example, sharks eyes are adapted with special color filters that allow them to see the biofluorescent signals of other animals, which could allow them to pass signals back and forth.

Biofluorescence 1

How does it work? 

Fluorescence happens when high intensity electromagnetic energy, such as UV light, excites an electron so that it jumps to a high-energy, unstable state. As the electrons fall back down to their natural resting place in the atom, they releases excess energy in the form of photons, or small packets of light, and the result is a colorful glow. This principle is used often in biological microscopy (illustrated below).

Biofluorescence 4

How do we know? 

While we don’t know much about biofluorescence yet, many scientists are undertaking studies to determine more about how it works and what purpose it might serve. To capture fluorescence, a photographer must shine high intensity blue light on an animal and then photograph it using a camera with a yellow filter that blocks out the blue, allowing the fluorescence to shine through. Dr. David Gruber and his team recently built “sharks-eye” view cameras to simulate fluorescent vision and investigate the underwater world from a fish-eye view. What they found was an amazing Technicolor carnival, starring many of the creatures we can find in our own coves at CIMI: Scorpionfish, swell sharks, and round rays!

What’s the deal with this secret underwater light show? It’s just one more mystery of the deep!

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