Plankton Facts & Worksheets

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Plankton is a varied group of creatures found in water (or air) that cannot propel themselves against a stream (or wind). Despite their small size, plankton is vital in marine ecosystems, serving as the foundation for the whole marine food web.

See the fact file below for more information on Plankton, or you can download our 33-page Plankton worksheet pack to utilize within the classroom or home environment.

Key Facts & Information

TERMINOLOGY

• Victor Hensen introduced the term “plankton” in 1887, derived from the Greek meaning “drifter” or “wanderer.”
• While particular forms can travel hundreds of meters vertically in a given day, their horizontal position is dictated mainly by the underlying water movement, and plankton moves typically with ocean currents.
• Some plankton drifts in this direction during their whole life cycle. Others are categorized as plankton, while they are small but grow large enough to swim against the currents.
• Plankton is typically minuscule, measuring less than an inch in length, although they sometimes include more significant organisms like crabs and jellyfish.

SIZE GROUPS

• Plankton is usually described in terms of their size. Typically the following divisions are used. 

• However, several of these categories, particularly on the larger end, may be interpreted with quite different bounds. Nano- and even smaller plankton were just found in the 1980s, yet they are thought to make up the most significant portion of all plankton in terms of number and variety.

TROPHIC GROUPS

• Plankton is classified mainly into broad functional (or trophic depth) groupings.
• PHYTOPLANKTON. This means python or plant in Greek. These prokaryotic or eukaryotic algae dwell on the water’s surface with enough light to enable photosynthesis. Diatoms, cyanobacteria, dinoflagellates, and coccolithophores are some of the most prominent groups.
• ZOOPLANKTON. This means zoon or animal in Greek. Small protozoans or metazoans (such as crustaceans and other animals) feed on other plankton. Larger nektonic animals’ eggs and larvae, such as fish, crabs, and annelids, are included.
• MIXOPLANKTON. Plankton has historically been classified as producers, consumers, and recyclers; however, certain plankton can benefit from more than one trophic level.
• Organisms with this mixed trophic strategy, known as mixotrophy, behave as both producers and consumers, either simultaneously or by switching between feeding modes in response to environmental circumstances.
• It allows them to grow through photosynthesis when nutrients and light are sufficient, then switches to consuming phytoplankton, zooplankton, or each other when conditions are poor.
• Constitutive mixotrophs (CMs) can perform photosynthesis on their own. In contrast, non-constitutive mixotrophs (NCMs) use neutrophils to engulf prey that is either kept alive inside the host cell, benefiting from its photosynthesis, or digested except for the plastids.

OTHER GROUPS

• Aside from the phytoplankton, zooplankton, and mixoplankton, there are other groups of plankton.
• GELATINOUS ZOOPLANKTON. They are delicate creatures in the ocean’s water column. Because they have no complex components, their fragile bodies are readily harmed or destroyed. 
• Transparent gelatinous zooplankton is common. 
• Most jellyfish are gelatinous zooplankton; however, not all gelatinous zooplankton are jellyfish.
• ICHTHYOPLANKTON. These are the fish eggs and larvae. Commonly found in the sunlight zone of the water column, which is less than 200 meters deep and is also known as the epipelagic or photic zone.
• Ichthyoplankton are planktonic organisms, which means they cannot swim successfully on their own and must drift with the ocean currents. 
• Early-stage larvae swim poorly, but as they grow into juveniles, they swim better and stop being planktonic. 
• Fish larvae are zooplankton that consumes smaller plankton, but fish eggs contain their food source.
• HOLOPLANKTON. They are planktic creatures during their entire life cycle. Meroplankton is planktic organisms that spend most of their life cycle in the benthic zone, unlike holoplankton. Most diatoms, radiolarians, dinoflagellates, and gastropod mollusk species are examples of holoplankton.
• MEROPLANKTON. Are a diverse group of aquatic animals with planktonic and benthic life stages. 
• Meroplankton differs from holoplankton, which spend their whole life cycle as plankton in the pelagic zone.
• Many of them transition to nekton or sessile on the bottom after spending time in the plankton.
• PSEUDOPLANKTON & TYCHOPLANKTON. Pseudoplankton is creatures that adhere to planktonic animals or other floating items like drifting timbers, buoyancy shells of organisms like Spirula, or artificial flotsam. Pseudoplankton has frequently been found in the digestive tracts of filtering zooplankters.
• Tychoplankton are species such as free-living or connected benthic invertebrates and other non-planktonic animals brought into the plankton by disrupting their benthic environment or by winds and currents.

HABITAT GROUPS

• Marine plankton – Marine plankton consists of marine bacteria, archaea, algae, protozoa, and drifter or floating animals living in salty seas and brackish estuaries.
• Freshwater plankton – Freshwater plankton are related to sea plankton; however, they are found inland in lakes and rivers.
• Aeroplankton –  are tiny life forms that float and drift in the air, propelled by the wind current; they are the atmospheric equivalent of sea plankton.
• Geoplankton – Many organisms survive in terrestrial environments by thriving in transitory, often minute water sources and moisture. 
• These include rotifers and gastrotrichs, which produce hardy eggs capable of lasting years in arid conditions and some of which can become dominant.

DISTRIBUTION

• In addition to aeroplankton, plants live in oceans, seas, lakes, and ponds. Virus local abundance horizontally, vertically, and seasonally, and the availability of light is the fundamental reason for this variation. 
• Solar energy drives all plants and ecosystems, limiting primary production to surface waters and geographical locations and seasons with plentiful light.
• Nutrient availability is a secondary variable. Although the tropical and subtropical seas have plentiful light, they have comparatively poor primary production because of inadequate nutrients such as nitrate, phosphate, and silicate. It is due to large-scale ocean circulation and stratification of the water column.
• Planktons are most prevalent in surface waters but can also be visible throughout the surrounding water. At depths where primary production is low, zooplankton consumes organic compounds sinking from more productive waterbodies.

ECOLOGICAL SIGNIFICANCE

• Food Chain – Plankton ecosystems have a part in the biogeochemical cycles of many essential chemical elements, including the ocean’s carbon cycle. 
• In addition, they represent the lowest levels of a food chain that sustains economically significant fisheries.
• Phytoplankton is considered the primary producers of a marine food web, while zooplankton is the primary consumers that feed off the phytoplankton.
• Fish larvae primarily consume zooplankton, which consumes phytoplankton.
• Carbon Cycle – Zooplankton primarily contributes carbon to the planktic food chain by feeding on phytoplankton, either as metabolic energy or as biomass or detritus. 
• Because organic material is denser than seawater, it sinks into open ocean environments away from coasts, transporting carbon.
• This mechanism, known as the biological pump, is one of the reasons why the oceans are the world’s most significant carbon sink. 
• Oxygen production – To make their energy, phytoplankton collect the sun’s energy and nutrients from the water. As a waste byproduct of photosynthesis, phytoplankton discharges molecular oxygen into the sea. 50% of the world’s oxygen is believed to be produced by phytoplankton photosynthesis. 
• Absorption efficiency – Plankton absorption efficiency is the amount of food consumed by the plant that affects how available the eaten organic materials are in satisfying the needed physiological demand. Depending on the feeding rate and prey species, differences in absorption efficiency may result in changes in fecal pellet production, which impacts how often organic material converts back to the marine environment.

BIOMASS VARIABILITY

• Phytoplankton population growth is influenced by light levels and nutrient availability. The main factor restricting growth in the world’s seas differs by area. 
• Phytoplankton growth in oligotrophic tropical and subtropical gyres is often limited by nutrient availability, whereas light frequently inhibits phytoplankton growth in subarctic gyres.

PLANKTONIC RELATIONSHIP

• Fish and Plankton – Zooplankton are practically the first meal of all fish larvae as they transition from yolk sacs to external feeding. Fish rely on zooplankton density and distribution to match that of new larvae, which might starve otherwise. Plankton may be patchy in maritime habitats where there are no substantial fish populations; moreover, in situations where fish are numerous, zooplankton dynamics are controlled by the fish predation rate.
• Whales and plankton – Whale feces is the ‘trophy’ in increasing nutritional availability among all animal feces. Phytoplankton is the driving force behind open ocean primary production, and they may absorb various nutrients from whale excrement. At the lower part of the marine food chain is phytoplankton consumed by zooplankton and krill that are preyed upon by larger and bigger marine animals, including whales; hence, whale feces feed the whole food chain.
• Humans and plankton – Humans are affected by plankton in various ways, both directly and indirectly. Around 70% of the oxygen in the atmosphere is produced in the seas by phytoplankton performing photosynthesis. Plankton can serve as an intermediate host for lethal parasites in humans.

PLANKTON DIVERSITY

• The following are the diversity that can be found in plankton. 
• The Pelagibacter ubique, the most common bacteria in the ocean has a major role in the carbon cycle of Earth.
• One of the significant contributors to our atmospheric oxygen is the tiny cyanobacterium Prochlorococcus.
• The major grazers of the plankton are the microzooplankton such as dinoflagellates and a tintinnid ciliate.

Plankton Worksheets

This is a fantastic bundle that includes everything you need to know about Plankton across 33 in-depth pages. These are ready-to-use worksheets that are perfect for teaching kids about Plankton, which is a varied group of creatures found in water (or air) that cannot propel themselves against a stream (or wind).

Complete List of Included Worksheets

Below is a list of all the worksheets included in this document.

1. Plankton Facts 
2. Fill in the Blank-TON
3. Planktonic Matches
4. Planktonic Groups Search
5. Two Plankton
6. Plankton Crossing
7. Plankton, Not Plankton
8. Plankton & Food Web
9. Planktonic Relationship
10. C.C & O.P
11. Secret Life of Plankton

Frequently Asked Questions

How long does plankton live?

While a bloom may stick around for weeks, any given phytoplankton only lives for days.

Why is plankton important?

Plankton is very important to Earth. They generate half of the atmosphere’s oxygen, which is as much as all the plants on land combined. Additionally, they form the base of almost every ocean food web – without them, most other marine life couldn’t exist.

Is plankton poisonous?

Although the majority of phytoplankton is non-threatening, there are some species that produce poisonous chemicals. These toxins can result in symptoms such as diarrhea, paralysis, and memory loss.

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