What is Plankton? The Real Monsters of the Ocean

icefish larva picture, what is plankton
Icefish larva, part of the plankton photo by: Wikimedia Commons

What is plankton? The Real Monsters of the Ocean

Night on the coral reef

As darkness slowly creeps over the coral reef, the night dwellers begin to appear. Coral relies upon its symbiotic algae to feed themselves during the day, but after dark the coral polyps unfold their sticky tentacles. These tentacles grab food (plankton) floating by in the water.

Black tip reef sharks, which have been snoozing lazily on the sandy bottom during the day, become violent predators. They travel in packs with some sharks flushing out and eating prey from the fish cowering in their reef lairs. Other sharks catch whatever the flushing sharks missed.

A chambered nautilus, the less sexy cousin of octopus and squid, slowly ascends from 2,000 feet deep to 300 feet deep, its shell’s chambers acting like a submarine’s ballast.

Plankton!

Then the real stars of the night show up, barely visible to the naked eye. The longest vertical migration takes place every night. Plankton rise from depths of 1,500 feet to feed near the surface.

I was lucky to see some of these other-worldly creatures on a Blackwater dive called “Pelagic Magic,” through Jack’s Diving Locker in Kailua-Kona on the Big Island of Hawaii. Divers hold onto ropes under the boat and like a seat back entertainment center on an airplane seat, each diver gets their own individual show. The highlight of my dive was seeing a squid flush red, catch a meal and dart to the surface, all in a blink of any eye.

Types of plankton

Plankton are the real monsters of the ocean, as the myriad of shapes and colors is outstanding. The larval form of many animals, like a crab or sea urchin, look nothing like the adults.

Much of the plankton is translucent because in the depths of the ocean they virtually disappear. Other plankton are bright red, which at the surface are obvious, but at depth they are barely visible. This is because red is the first color to be lost under the water. The further down you descend in the ocean, the less colors you see.

Phytoplankton vs. Zooplankton

There are two main types of plankton, the phytoplankton vs. zooplankton. “Phyto” means plant in Greek, and “Zoo” means animal (think of what lives at a zoo!). So the phytoplankton are the plants of the ocean, while the zooplankton are the animals of the ocean. Phytoplankton are very important because they make up the base of the food web, and they are responsible for one out of every two breaths you take! Just like how animals on land eat plants (do you eat your veggies?), the zooplankton depend on the phytoplankton for food. And plenty of larger animals-fish, whale sharks, manta rays, baleen whales-depend on plankton for as their food.

Did you know krill (part of the plankton) are the most abundant animal on Earth?

By-the-Wind Sailors Washing Up on US West Coast Beaches

Velella velella
By-the-Wind-Sailors or Velella velella photo from Wikipedia

By-the wind sailors, also known by their scientific name Velella velella, have been washing up by the thousands along the West Coast of the United States. They have been found from Monterey, California all the way up the coast to Oregon.

What are Velella? They are distantly related to jellies as both are cnidarians. Velella are closely related to the Portuguese Man of War. They have a blue elliptical base and a transparent triangular “sail.” An individual is actually a hydroid polyp. A polyp is like the less recognizable stage in a jelly’s life when it is anchored to the sea floor, though Velella polyps are free-floating. In this polyp form, they spend their whole lives at the surface. Velella are at the mercy of the wind to get anywhere. They are found in warm and temperate oceans.


Velella eat by using their tentacles which hang beneath the surface. Like jellies, the tentacles have nematocysts, or stinging cells, to catch their food. These stinging cells are not dangerous to humans, though each person’s tolerance to their venom varies.

There are two forms of Velella. One has a left-to-right orientation of its sail, and the other form has a right-to-left orientation of its sail.

The Velella life cycle (like many “jelly-like” creatures) can be summarized as polyp-medusa-egg-planula-polyp. The polyp stage is the one written about in this post. The medusa is the free-floating stage, like any jelly you can think of. The eggs are microscopic and part of the plankton. Planula are the “free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species,” i.e. the fertilized egg.

Next time you are at the beach, look for these By-the-Wind Sailors!

Sources used: Univ. of Michigan animal diversity page

San Francisco Chronicle article “Beached blue wonders”

Wikipedia page on planula

Krill: The Most Abundant Animal on Earth

Euphasia superba
Krill (Euphasia superba)photo from Wikipedia

Or specifically, the most biomass on Earth. That would be krill, the small shrimp-like creatures like large whales love to gobble down.

My name is Karl, and I am a krill. I live in Antarctic waters. What is it like to be part of a collective or large group? Well, not only am I small at half an inch long, but I live in a swarm of krill. A swarm of krill may be as dense as 10,000 individuals per cubic meter and may stretch for many kilometers. The total biomass, or the total weight of krill is estimated at 379 million tons. Half of that is eaten by animals such as whales, seals, penguins, squid and fish each year! So my life expectancy is less than a year unless I’m lucky. That is if I don’t get caught by a krill fishery either. Krill is used in supplements, aquaculture, aquarium trade, as bait and as food for humans in places such as Japan and Russia.

As a wee lad, I ate microscopic food stuck to the ice. I also depended on the ice for shelter from predators. Climate change is causing the sea ice to melt earlier in the season, and this is a problem for young krill. Some krill populations have declined up to 80% due to climate change.

Let’s hope climate change doesn’t wipe out my species, as it would be detrimental to animals higher on the food chain like whales and seals.

10 Endangered Ocean Animals: Happy Endangered Species Day!

Hector's Dolphin
Maui's Dolphin photo by WWF/Will Rayment

10 Endangered Marine Animals

1. Maui’s Dolphin: found off of New Zealand, only 55 individuals remain

2. Northern Right Whale: found in Atlantic Ocean, only 350 individuals remain

3. Vaquita: small dolphin found off of Baja Peninsula, Mexico, 500-600 remain

4. Mediterranean (less than 400 remain) and Hawaiian Monk Seals (approximately 1100 remain)

5. Sea Turtles: 6 or the 7 species of sea turtles are endangered (Green, Hawksbill, Kemp’s Ridley, Leatherback, Loggerhead, and Olive Ridley)

6. Staghorn Coral: has declined by 98% in the Caribbean since 1980

7. Beluga Sturgeon: hunted for their caviar (eggs), 1100 remain in the Caspian Sea

8. Coelacanth: an ancient order of fishes, considered the most endangered order in the world

9. Southern Sea Otter: up to 2,300 individuals remain

10. Bluefin Tuna: as few as 25,000 mature individuals remain

Disclaimer: There are hundreds of ocean species that are endangered (1,000’s if you consider the animals and plants we have yet to discover). I chose the top ten endangered species that I felt people might have heard of.

UPDATE: As of May 2015 less than 100 Vaquita remain

Sources: allaboutwildlife.com
marineinsight.com
World Wildlife Fund
wonders-world.com
Smithsonian Ocean Portal

10 Jellyfish Facts for Kids

Jellyfish facts largest & smallest
Lion's Mane Jellyfish: the largest jelly in the ocean

10 Jellyfish Facts for Kids

1. A jellyfish is not a fish at all, it is an
invertebrate (animal without a backbone).

2. Invertebrates make up 95% of all animals on earth.

3. A jelly is made up of approximately 95% water.

4. A jelly does not have a brain, eyes, bones, teeth, or blood.

5. A jelly reproduces by making clones of itself (exact copies of itself) so it technically never dies.

6. There are 2 main stages to a jelly’s life cycle, the sessile (stuck to a surface) polyp, and the free-swimming medusa (what you think of as a jelly).

7. The largest jelly ever found was a Lion’s Mane Jelly with a diameter of 7 feet 6 inches (2.29m) and its tentacles trailed 120 feet behind it!

8. The smallest jelly is the Irukandji jelly which is only 1 1/2 inches in diameter.

9. Jellies are found in all the world’s oceans.

And the last jellyfish fact for kids is:

10. A box jelly (sea wasp) sting can kill you within 2-3 minutes.

10 Facts About the Lion’s Mane Jellyfish
10 Jellyfish Facts for Kids and Jelly Enthusiasts