Plankton are an essential component of life on Earth. Marine plankton, found in all ocean ecosystems, play a critical role in maintaining the health and balance of the ocean and its complex food webs. The oxygen, nutrients, and biomass they produce also sustain terrestrial life—from the food we eat to the air we breathe. 
 
Plankton—derived from the Greek root planktos, meaning “wanderer” or “drifter”—are unable to swim against currents, tides, or waves. The word refers to the numerous organisms floating throughout aquatic ecosystems.
 
Phytoplankton are the tiny, plant-like producers of the plankton community. They include bacteria and algae that form the base of aquatic food webs. Common phytoplankton include diatoms, dinoflagellates, cyanobacteria (blue-green algae), and green algae. Through photosynthesis, phytoplankton use sunlight, nutrients, carbon dioxide, and water to produce oxygen and nutrients for other organisms. With 71% of the Earth covered by the ocean, phytoplankton are responsible for producing up to 50% of the oxygen we breathe. These microscopic organisms also cycle most of the Earth’s carbon dioxide between the ocean and atmosphere
 
Zooplankton are the animal-like primary consumers of plankton communities. In turn, zooplankton then become food for larger, secondary consumers such as fish. Zooplankton include microscopic and macroscopic organisms. Some zooplankto—such as copepods, krill, and arrow worms—will drift the ocean as plankton for their entire lives. Other zooplankton live only a portion of their lives as ocean drifters. These include oysters, crabs, and some fish. 
 
Plankton also play a role at the end of the food web—as decomposers and detritivores. These plankton, including bacteria, fungi, and worms, break down and consume dead plant and animal material that falls through the water column as "marine snow." Marine snow often includes fecal matter, sand, soot, skin, and other organic and inorganic particles descending to the seafloor.
 
Through plankton sampling, scientists like Richard Lampitt can monitor this important component of life on Earth.
  1. What are some different ways to classify plankton? 

     

    • Answer

      Plankton can be classified in numerous ways, including

      • size
      • shape
      • distribution
      • producers or consumers
      • phytoplankton or zooplankton
      • whether the organisms are temporary or permanent plantonic creatures

  2. Why do Dr. Lampitt and his team find more phytoplankton at the top of the water column (near the ocean surface)?

     

    • Answer

      Phytoplankton rely on sunlight (as well as temperature and nutrients) for photosynthesis. Sunlight only permeates the upper layers of the ocean, called the epipelagic or euphotic zone. Below this zone, few phytoplankton have the necessary sunlight for photosynthesis.

  3. How are people dependent on ocean plankton for their survival and health?

     

    • Answer

      1) Ocean phytoplankton provide up to 50% of the oxygen we breathe.

      2) Ocean plankton are the base of the ocean food web. These food webs provide food and financial resources to billions of people around the world.

      3) Phytoplankton uptake carbon dioxide. This makes them an important part in the regulation of climate change.

  • Foraminifera (forams) and radiolarians are microscopic zooplankton. The tests, or shells, of these plankton are so abundant that they form the majority of seafloor sediment in many parts of the ocean. The chemicals found in foram tests are also be used by oceanographers to study what the Earth’s climate was like in the past.
  • Plankton provide the most ancient evidence of life on Earth. Stromatolites are thin layers of fossilized cyanobacteria (a type of plankton) that date from between 2.8 billion to 3.5 billion years ago.
  • Marine snow got its name because it looks like snowflakes sinking down to the bottom of the ocean. Some marine “snowflakes” can grow to be more than 5 centimeters (1.9 inches) in diameter and can take weeks to reach the seafloor.
algae
Plural Noun

(singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds.

aquatic
Adjective

having to do with water.

arrow worm
Noun

predatory marine worms that drift in the deep sea as plankton.

Noun

layers of gases surrounding a planet or other celestial body.

Plural Noun

(singular: bacterium) single-celled organisms found in every ecosystem on Earth.

biomass
Noun

living organisms, and the energy contained within them.

copepod
Noun

microscopic marine organism (crustacean).

Noun

steady, predictable flow of fluid within a larger body of that fluid.

cyanobacteria
Noun

type of aquatic bacteria that can photosynthesize light to create energy. Also called blue-green algae (even though it is not algae) and (in freshwater habitats) pond scum.

decomposer
Noun

organism that breaks down dead organic material.

detritivore
Noun

organism that consumes dead plant material.

diatom
Noun

type of algae, most of which are only one cell.

dinoflagellate
Noun

one-celled marine organism that is a major component of plankton.

Noun

community and interactions of living and nonliving things in an area.

fecal
Adjective

having to do with excrement.

Noun

all related food chains in an ecosystem. Also called a food cycle.

fungi
Plural Noun

(singular: fungus) organisms that survive by decomposing and absorbing nutrients in organic material such as soil or dead organisms.

inorganic
Adjective

composed of material that is not living, and never was, such as rock.

krill
Noun

small marine crustacean, similar to shrimp.

marine
Adjective

having to do with the ocean.

marine snow
Noun

continuous fall of organic and inorganic particles (including the remains of marine organisms, fecal matter, shells, and sand) from the upper layers of the water column to the seafloor.

microscopic
Adjective

very small.

Noun

substance an organism needs for energy, growth, and life.

organic
Adjective

composed of living or once-living material.

Noun

process by which plants turn water, sunlight, and carbon dioxide into water, oxygen, and simple sugars.

phytoplankton
Noun

microscopic organism that lives in the ocean and can convert light energy to chemical energy through photosynthesis.

Plural Noun

(singular: plankton) microscopic aquatic organisms.

primary consumer
Noun

organism that eats plants or other autotrophs.

producer
Noun

organism on the food chain that can produce its own energy and nutrients. Also called an autotroph.

sampling
Noun

a small part of a group observed and tested to represent the whole group.

secondary consumer
Noun

organism that eats meat.

soot
Noun

sticky black particles produced as some fuels, such as coal and wood, are burned. Also called black carbon.

terrestrial
Adjective

having to do with the Earth or dry land.

Noun

rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.

water column
Noun

area reaching from the sediment of a body of water to its surface.

wave
Noun

moving swell on the surface of water.

zooplankton
Plural Noun

microscopic, heterotrophic organism that lives in the ocean.

Funder

This material is based in part upon work supported by the National Science Foundation under Grant No. DRL-1114251. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.