Phytoplankton Vs Zooplankton: An Overview
Phytoplankton Definition
The free-floating microalgae known as phytoplankton play a significant role in the ecosystems of the ocean, sea, and freshwater bodies of water.
- The terms “phyto” and “plankton,” which both imply drifter in Greek, are combined to form the word “phytoplankton.”
- Since phytoplanktons get chlorophyll to produce their own nourishment, they are autotrophic, much like terrestrial plants.
- The majority of phytoplankton are seen floating on the surface of bodies of water because they need sunshine to prepare their meal.
- Although phytoplanktons are so small that an unaided eye cannot detect them, they are visible as colorful patches on the water’s surface when they are present in large numbers.
- About 1% of the world’s biomass is made up of phytoplankton. The majority of freshwater and marine creatures eat these organisms as their main source of nutrition.
- Depending on different substrates, temperature, and the availability of adequate sunshine, phytoplankton concentrations may vary.
- Diatoms, cyanobacteria, dinoflagellates, green algae, and other different species make up phytoplankton.
- During photosynthesis, these creatures use a variety of inorganic minerals to produce proteins, carbohydrates, and other nutrients for themselves and other animals.
- In contrast to other autotrophs like plants, phytoplankton is made up of a variety of different types of organisms, from bacterial or archaeal prokaryotes to protistan eukaryotes.
- Half of all photosynthetic activity on Earth is accounted for by phytoplankton, which is also the main contributor to the marine and freshwater food webs.
- These are the main food sources in aquaculture and mariculture and are also used as dietary supplements for different invertebrates in aquariums.
- When nutrients are present in excessive numbers, phytoplankton may grow out of control, developing algae blooms.
- These blooms might create poisonous or even lethal compounds that could disrupt the habitat’s other ecosystems.
- Based on research done between 2015 and 2019, it was shown that global warming is causing the phytoplankton concentration to drop by around 1% per year.
- Diatoms, green algae, cyanobacteria, and coccolithophores are a few examples of phytoplankton.

Zooplankton Definition
Most of the heterotrophic creatures in marine settings are composed of tiny, floating organisms known as zooplankton.
- The name “zooplankton” is derived from the Greek terms “zoo,” which means “animals,” and “plankton,” which means “drifter.”
- In aquatic ecosystems ranging from freshwater to seas and oceans, zooplankton plays an essential role in food chains.
- As heterotrophs, zooplankton rely on phytoplankton and other autotrophs as a source of energy and carbon.
- They can locate food and defend themselves from predators thanks to mobility and water.
- Small protozoans and large metazoans are only a few examples of the creatures that make up zooplanktons. Other creatures, such as immature starfish and worms, may also serve as transient zooplanktons.
- Like phytoplankton, zooplankton species include cnidarians, crustaceans, chordates, mollusks, radiolarians, foraminiferans, and dinoflagellates.
- The majority of zooplankton are the larval stages of fish and invertebrates that eventually go through metamorphosis to become mature marine animals.
- Predation, competition, and breeding are a few of the reasons that limit the dispersal of zooplankton.
- Furthermore, patches of zooplankton can be found in places with favorable environmental factors such as salinity, temperature, and water currents.
- The existence of phytoplankton also restricts the amount of zooplankton, and phytoplankton can have their life cycle interrupted by other variables.
- Zooplankton serves as a food source for higher consumers like fish, making them a crucial component of ocean food chains.
- They may even serve as a conduit for the packing of organic elements in the biological bumps, making this group of creatures significant.
- They also quickly counteract the growing phytoplankton population, causing blooms and halting the negative impacts.
- Some zooplankton has also been linked to removing hazardous substances like mercury from water pollution.
- However, by hosting harmful organisms, zooplanktons also aid in the survival and spread of many illnesses.
- A symbiotic connection exists between bacteria like Vibrio cholerae and crustacean zooplanktons because the exoskeleton of these animals provides the carbon and nitrogen that the bacteria need to survive.
- Animals like radiolarians, krill, jellyfish, immature mollusks, and amphipods are some examples of zooplankton.
Key Differences (Phytoplankton Vs. Zooplankton)
Basis for Comparison | Phytoplankton | Zooplankton |
Definition | Phytoplankton is a group of free-floating microalgae that drifts with the water current and forms an important part of the ocean, sea, and freshwater ecosystems. | Zooplankton is a group of small and floating organisms that form most of the heterotrophic animals in oceanic environments. |
Terms | ‘Phyto’ refers to ‘plant-like.’ | ‘Zoo’ refers to ‘animal-like.’ |
Consists of | Phytoplanktons consist of diatoms, cyanobacteria, dinoflagellates, green algae, and coccolithophores. | Zooplanktons consist of organisms like radiolarians, foraminiferans, dinoflagellates, cnidarians, crustaceans, chordates, and mollusks. |
Nutrition | Phytoplanktons are autotrophic and, thus, can make their own food with sunlight and chlorophyll. | Zooplanktons are heterotrophic, depending on the distribution of phytoplankton for their food and energy. |
Habitat | Phytoplanktons are found mostly floating on the surface of water bodies as they require sunlight for photosynthesis. | Zooplanktons remain mostly around the dark and deeper areas of water. |
Appearance | Phytoplanktons are seen as cloudy green patches on water. Otherwise, they appear brown in color. | Zooplanktons are mostly translucent, but their shape, size, and color might differ with the type of the organism. |
Size | Phytoplanktons are invisible to the unaided eyes and can only be seen as green patches when present in large numbers. | Most zooplanktons are large enough to be seen with the naked eye. |
Photosynthesis | Phytoplanktons are capable of photosynthesis, being responsible for about half of the photosynthesis performed around the world | Zooplanktons are not capable of photosynthesis. |
Oxygen release | Phytoplanktons are photosynthetic and thus are extremely important for oxygen release. | Zooplanktons only take in oxygen and do not produce it. |
Energy | Phytoplanktons obtain their energy via photosynthesis by utilizing inorganic minerals. | Zooplanktons obtain their energy by feeding on phytoplankton. |
Position in the food chain | Phytoplanktons are the producers of oceanic food chains. | Zooplanktons are the primary or secondary consumers of the oceanic food chain. |
Movement | Most phytoplanktons are not capable of freely moving with water currents. | Zooplanktons are capable of moving with or against water currents against predators or competitors. |
Metamorphosis | Phytoplanktons do not undergo metamorphosis. | Most zooplanktons are larval forms of fishes and invertebrates that eventually metamorphose to form free-swimming creatures. |
Vertical migration | Phytoplanktons are not capable of vertical migration. | Zooplanktons are capable of vertical migration in water. |
Functions | Phytoplanktons act as food for zooplankton and as indicators of the health of the marine environments. | Zooplanktons are the indicators of toxic substances present in the ecosystems and also serve as food for higher heterotrophs. |
Examples | Some examples of phytoplankton include diatoms, green algae, cyanobacteria, and coccolithophores, among others. | Some examples of zooplanktons include animals like radiolarians, krill, jellyfish, young mollusks, and amphipods, among others. |
Examples of Phytoplanktons
1. Cyanobacteria
- Cyanobacteria are photosynthetic bacteria that are mostly found in water and use sulfur compounds to chemosynthesis their food.
- Since cyanobacteria are autotrophs and create most of the oxygen in marine settings. They are also known as blue-green algae.
- These make up a sizable subgroup of phytoplankton and are dispersed evenly over all the world’s water bodies. Additionally, cyanobacteria come in various forms, dimensions, and hues.
- Since they are more resilient than other phytoplanktons and can thus endure even harsh aquatic settings, most cyanobacteria are well-suited for various aquatic environments.
- These are primarily found in colonies made up of filamentous or unicellular colonies that are dispersed randomly throughout water bodies.
- Different biomasses are created in distinct regions when the colonies divide from each other to occupy different sites. Lyngbya, for example, has the potential to produce flowers.
- Like other phytoplanktons, cyanobacteria are a source of food for zooplankton.
- Oceanic ecosystems are home to cyanobacteria like Synechocystis, Oscillatoria, Lyngbya, etc.
You may also like to read: Biotic Factors
2. Dinoflagellates
- These unicellular creatures have golden-brown plastids, which give them their golden color.
- The majority of dinoflagellates coexist harmoniously with one another by consuming inorganic minerals and giving them enough oxygen.
- They feature a dented cell membrane, characteristic swimming patterns, a sizable nucleus, and chromosomes that can be seen.
- They are known as dinoflagellates because of the two different flagella that protrude from their cell membrane.
- Despite being an essential component of phytoplanktons that help the ecosystem by providing food and oxygen, they might be dangerous if they grow into blooms.
- Some of them even release poisonous compounds that are damaging to nearby plants and animals.
- Dinoflagellates include organisms including Oxyrrhis marina, Symbiodinium, and Dinophysis acuminate.
Examples of Zooplanktons
1. Jellyfish
- An example of zooplankton that can swim and float through oceans is the jellyfish.
- Nearly every area of the water is home to hundreds of jellyfish, which are all members of the sea anemone or coral family.
- Jellyfish have soft, translucent body that resembles an umbrella and are surrounded by tentacles that dangle off of them. The structure is known as the medusa.
- Jellyfish may be as small as microscopic organisms or as large as one meter in length.
- Zooplanktons like jellyfish serve as a connection between phytoplankton and higher animals since ocean food chains are often shorter than those on land.
- However, the fact that there are more of these jellyfish than usual might potentially be a concern because some of them are large enough to eat the larvae of small fish.
2. Krill
- Krill is an essential component of zooplanktons, a type of crustacean found in oceans all over the world.
- During the day, krill may be seen on the water’s surface; but at night, they migrate deeper into the ocean.
- These are often primary consumers at a lower trophic level, acting as a link between phytoplankton and secondary or tertiary consumers.
- The majority of krill serve as food for bigger marine species.
- Since they may be utilized as food for aquaculture and mariculture, some of them are even caught for commercial purposes.
- They have a chitinous exoskeleton that is primarily transparent, like most crustaceans.
- Krill are bioluminescent creatures with light-emitting photophores that may be crucial for direction and mating.
References
- Difference between Phytoplankton and Zooplankton
- Phytoplankton vs Zooplankton