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What causes waves to glow?

A friend requested bioluminescent waves, and how could I say no to that!? Apparently, there are glowing waves happening off the Southern California coast... how cool is that? There are even some photos of dolphins swimming through the ocean and leaving glowing trails! What causes this phenomenon?

Well, surprisingly enough, that icky "red tide" in the ocean is actually glowing waves by night!

When a dinoflagellate population increases to such large numbers that it discolors the water it is known as a red tide. The environmental conditions which result in the "bloom" of red tides are not completely understood, nor predicable. A dinoflagellate red tide discolors the water to red or brown due to as many as 20 million cells per liter! These red tides are composed primarily of one species of dinoflagellate that has been rapidly growing and accumulating.

Some red tides are luminescent; most of the red tides in southern California create nighttime displays of bioluminescence in the wakes breaking on the beach, or in the wake of a boat, or even the trail of dolphins! A widely accepted theory says bioluminescence in dinoflagellates is a defense mechanism used to scare off predators, or more likely, alert larger predators who will eat the current predator grazing by the dinoflagellates... an enemy of my enemy is a friend?

Predators are not uncommon for dinoflagellates as they are a type of phytoplankton which are very small. Although many of them are microscopic and range from 15 to 40 microns in size, the largest, Noctiluca, may be up to 2 mm in diameter... so probably best to alert that nearby shark if a small fish is passing by you as a tiny plankton.

If you haven't already, you should look up the pictures of these bioluminescent waves, but especially look for the pictures of the glowing dolphins! It is well worth the time.

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