Dinoflagellates: Bioluminescent Algae

In some oceans when the night is dark enough, you can see the waves glow as the water stirs. This is caused by phytoplankton called dinoflagellates. They give off a soft blue glow when disturbed. The chemicals they use are similar to the ones causing lightning bugs to glow.


When a person swims through the algae, the motion gives off a glow all around them, looking like angel's wings. Boats and wave action can also cause ripples of light to cascade in their wake. This video was taken at a dock in Australia where this algae is plentiful. People throw water on it to cause it to glow in amazing patterns.

Phytoplankton

Now that I have discussed some of the biggest animals in the ocean, I will now talk about the smallest. The basis of the ocean's food chain is phytoplankton. The term phytoplankton refers to thousands of species of tiny plants and algae that live in the ocean. Phytoplankton work like other plants, turning sunlight and carbon dioxide into energy and oxygen. The phytoplankton in the ocean are responsible for over 50% of all oxygen in our atmosphere.

Phytoplankton comes in many shapes and sizes and all are microscopic. Any time you swim in the ocean, you are immersed in a soup of living plants. Murkier water tends to have more abundant plankton where clear water has very little.

Phytoplankton are the first step in most food chains in the ocean. Tiny animals called zooplankton eat phytoplankton. Larger animals eat zooplankton, and bigger fish and animals eat them. Many larger animals eat just phytoplankton as well. Whale sharks, the biggest fish in the world, eat nothing but phytoplankton.

Whale Shark

Whale Sharks are the biggest fish in the world. Blue whales are far bigger, but they are air breathing marine mammals. Whale sharks can grow up to 40 feet long and weigh up to 15 tons. Strangely enough, they are one of only 3 species of sharks in the ocean that are not harmful to humans. In fact they are often photographed swimming peacefully with divers.

These gentle giants do not have the rows of razor sharp teeth fitted in most of their relatives. Instead of prowling constantly in search of blood, they casually glide through the ocean with their huge mouths open wide. They are filter feeders. This means they strain out microscopic plankton from the ocean around them as their food. They are another example of one of the biggest animals in the ocean feeding on some of the smallest.