PLANKTON POWER — FIVE PLANKTON FACTS
by Mack Ross, Educator
1) Not all plankton are microscopic
Sea Nettle Jelly
Did you know that the word plankton means to wander or drift? Plankton describes all of the organisms that are carried by ocean currents rather than actively swimming. You may be surprised to learn that jellies are considered plankton! These gelatinous animals spend their entire lifecycle drifting through the water — they truly “go with the flow.” Given that tentacles of local jelly species, like the lion’s mane jelly, can reach a length of 120ft (36.5m), it is safe to say that not all plankton are microscopic.
Plankton can be broken down into two broad categories: phytoplankton (plants!) and zooplankton (animals!). Just like land plants, phytoplankton undergo photosynthesis to obtain energy from the sun. Zooplankton are animals that typically consume phytoplankton, or other zooplankton, in order to acquire energy and grow. Many zooplankton species, like copepods, stay microscopic through their entire lifecycle. Other types of zooplankton begin life as microscopic organisms, but then grow into larger animals. Sea stars, barnacles, sea urchins and octopuses all begin as plankton!
2) Plankton migrate
When considering the greatest migrations in the animal kingdom, many people may think of wildebeests traveling through the Serengeti or the Arctic tern flying from the North to South pole. Surprise! Zooplankton undertake the largest animal migration. Each day, zooplankton travel from the upper layers of the ocean near the surface to the deeper, intermediate waters. This process is known as diel vertical migration and is driven by the predator and prey dynamics being navigated by zooplankton.
Phytoplankton live near the surface because they require sunlight for photosynthesis. Despite wanting to feast on these phytoplankton, zooplankton will spend daylight hours in deeper water to avoid predation. Baleen whales, fish, and birds, zooplankton’s predators, prefer to feed during the day given the advantage of sight. Under the moonlight, zooplankton migrate back up to the surface to feed on phytoplankton. Covering vertical distances of up to 1,000m, the migration of zooplankton is spectacular.
Winter Ocean Clarity, Ogden Point, Victoria
3) Plankton reproduction impacts water clarity
In winter months, the Salish Sea is much clearer, almost appearing tropical. Why? Plankton! The seasonal shift from winter to spring brings more sunlight and animal reproduction. Just as bald eagles and other birds begin nesting in late winter and spring, a lot of marine species also begin reproducing in the springtime.
Red Urchin Spawning
Check out this red sea urchin! Spawning is a common method of reproduction in the ocean. This urchin is releasing its eggs into the water with the goal it will come into contact with the sperm. If this process is successful, larval sea urchins, considered zooplankton, will feed on phytoplankton. With the cumulative reproduction of many species, and an increase in phytoplankton (more sunlight = more phytoplankton!), waters become murkier and there is a noticeable decrease in visibility in the spring and summer. (Just ask a diver!)
4) Phytoplankton produce oxygen and regulate atmospheric carbon levels
The cycle of photosynthesis in phytoplankton is important because they not only make oxygen available but they also help remove carbon from the atmosphere! Old growth forests and mangrove systems get a lot of credit for their ability to provide clean air, but more than half the air we breathe comes from phytoplankton.
When phytoplankton are consumed by zooplankton, or otherwise perish, the carbon they sequestered sinks to the bottom of the ocean. This movement of carbon into the deep ocean is important because it eventually becomes buried by sediment. This process of carbon absorption and transfer is significant because it helps decrease carbon in other Earth reservoirs, such as the atmosphere, creating a more habitable climate for all other species.
5) Plankton form the base of our marine food webs
We marvel at beautiful fish, sea stars and marine mammals, but the success of these organisms is directly related to the base of the marine food web — plankton! Even though many plankton are too small to observe with your naked eye, it is vital that we understand and appreciate these organisms because they help maintain the balance, and overall health, of marine food webs. Next time you are admiring the amazing marine life of the Salish Sea or feeling grateful for fresh, clean air — you should thank plankton!