Difference Between Plankton and Nekton

Main Difference – Plankton vs Nekton

Plankton and nekton are two types of marine aquatic organisms. The main difference between plankton and nekton is that plankton are passive swimmers that are carried by the water currents whereas nekton are actively-swimming organisms that swim against the water currents. Plankton possess a Reynolds number less than 10 while nekton possess a Reynolds number greater than 1000. Reynolds number predicts the transition of the flow from laminar to turbulent. Some organisms begin their life as plankton and then transit to nekton later. Plankton can be microscopic animals such as diatoms, dinoflagellates, coccolithophores, foraminifera, and radiolarian and larvae of marine animals such as crabs and sea stars as well as larger organisms like jellyfish and floating sargassum weed. Nekton include fish, whales, and squids.

Key Areas Covered

1. What are Plankton
      – Definition, Characteristics, Examples
2. What are Nekton
      – Definition, Characteristics, Examples
3. What are the Similarities Between Plankton and Nekton
      – Outline of Common Features
4. What is the Difference Between Plankton and Nekton
      – Comparison of Key Differences

Key Terms: Bacterioplankton, Marine Organisms, Nekton, Phytoplankton, Plankton, Water Currents, Zooplankton

What are Plankton

Plankton are marine organisms that drift in the water. They can be either plants or animals, and they live in the upper to middle levels of the sea (pelagic zone). The horizontal migration of plankton is determined by the water currents. Plankton are shown in figure 1.

Figure 1: Plankton

Phytoplankton, zooplankton, and bacterioplankton are the three types of plankton. The phytoplankton are the photosynthetic organisms that live near the water surface. They comprise chlorophyll. Phytoplankton bloom is a rapid growth of phytoplankton in a water body. Phytoplankton are the primary producers of the marine food web. Diatoms, dinoflagellates, coccolithophores, and green algae are phytoplankton. The zooplankton are translucent microscopic animals such as crustacean, jellyfish, and small protozoa that feed on other plankton. Bacteria and archaea are bacterioplankton.

What are Nekton

Nektons are marine animals that can swim against the water currents. Some chordates such as bony fish and cartilaginous fish, reptiles such as snakes, turtles, and saltwater crocodiles, and mammals such as porpoises, whales, and seals are considered as nekton. Squids and octopods are molluscan nekton. Decapods such as crabs, lobsters, and shrimps are arthropod nekton. Herbivorous nektons are less common while zooplankton feeders are prominent. Some nektons are scavengers. A nekton is shown in figure 2.

Figure 2: Nekton

The vertical distribution of nekton depends on the nutrient supply, temperature barriers, and the salinity. Different nektonic species are found at different depths in the ocean.

Similarities Between Plankton and Nekton

Both plankton and nekton are marine aquatic organisms.
Both plankton and nekton can be animals.
Both plankton and nekton can be macroscopic.

Definition

Plankton: Plankton refers to marine organisms that drift in the water.

Nekton: Nekton refers to the marine animals that can swim against water currents.

Swimming

Plankton: Plankton are passive swimmers that flow along water currents.

Nekton: Nekton can actively-swim against water currents.

Reynolds Number

Plankton: Plankton possess a higher Reynolds number greater than 1000.

Nekton: Nekton possess a lower Reynolds number less than 10.

Microscopic/Macroscopic

Plankton: Plankton can be either microscopic or macroscopic.

Nekton: Nektons are macroscopic.

Animals/Plants

Plankton: Plankton can be either plants or animals.

Nekton: Nektons are animals.

Examples

Plankton: Plankton can be either microscopic animals such as diatoms, dinoflagellates, coccolithophores, foraminifera, and radiolarian or larger organisms like jellyfish and floating sargassum weed.

Nekton: Examples of nektons include fish, whales, turtiles, saltwater crocodiles, crabs, lobsters and squids.

Conclusion

Plankton and nekton are two types of marine organisms. Plankton are passive swimmers who change their position in the water body along with the water currents. In contrast, nekton can actively-swim against the water currents. Therefore, the main difference between plankton and nekton is their type of swimming.

Reference:

1.“Plankton Facts ~ What is Plankton?” Orma – Oceanic News, Facts & FAQ, 13 Jan. 2015, Available here.
2.“Nekton.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 6 Sept. 2016, Available here.

Image Courtesy:

1. “Plankton collage” By Kils at the German language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “Schwimmender-Pinguin” By Wilfried Wittkowsky – Own work (CC BY-SA 3.0) via Commons Wikimedia