Plankton, phytoplankton and zooplankton are found everywhere in the oceans. Here's an overview of these different types.
Plankton is made up of one-celled plants through almost every animal phylum on earth. Planktonic organisms that are plants are called phytoplankton and the animals are called zooplankton. All planktonic organisms are at the mercy of the currents. However, most planktonic organisms do have some locomotion, but it is minute compared to the force of the currents. Additionally, some plankton organisms have methods to move up and down the water column feeding near the surface at night and further down the water column during the day.
Plankton is mostly found in the euphotic zone, the upper layer of water that receives enough light for photosynthesis to take place. The mostly one-celled phytoplankters receive their energy from the sun. This energy is transferred to multi-celled zooplankters as the phyto plankton is eaten, then to a little larger animal, etc. and the food chain is started. All life in the oceans (there is some diversion of this statement at deep-sea vents) is dependent on the phytoplankton populations in the top 100 meters of the ocean. Scientists who study plankton feel that the phytoplankton is the most essential ecological population on earth. Zooplankton can inhabit the water column on down to the abyssal zone, but they are found in less quantities below the euphotic zone.
Let’s take a look at the different types of plankton.
Phytoplankton: These are the one-celled, chlorophyll-bearing organisms which form the base of the food chain in the oceans.
Zooplankton: These are all the animal planktonic organisms that are at the mercy of the currents.
Holoplankton: These are the zooplankton organisms that spend all their lives in the plankton ecosystem.
Meroplankton: These are the animals that spend part of their lives as a plankter, usually the larval stages, and then grow into the adult stages as nekton (swimming against the currents).
