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Plankton Words: “phytoplankton” to “zooplankton”,
Part 2 of 2.

plankto-, plankt-, -plankton (Greek: passively drifting, wandering, or roaming)

phytoplankton, phytoplankters, phytoplanktonic:
Planktonic plant life; typically comprising suspended microscopic algai cells such as diatoms and desmids.

Marine life is classified into three groups: benthos, nekton, and plankton.
  • Benthos refers to the plants and animals living on the sea bottom; such as, the permanently fixed or immobile forms (sponges and corals), the various creeping forms (crabs, snails), and others that burrow.
  • Barnacles, the larger seaweeds, and sea squirts are also members of this benthos group.
  • Nekton are swimming animals that can move freely and that are capable of migration from one place to another.
  • Plankton are the floating and drifting small animals (zooplankton) and plants (phytoplankton) capable of very limited locomotion, if any.
  • Animal life of one kind or another exists at all depths of the oceans and in great abundance; indeed, nearly half of all classes of animals are marine.
  • Plant life is much less abundant and consists chiefly of the phytoplankton and the large seaweeds and algae.
  • The animal life is almost entirely dependent on the phytoplankton for its existence and these minute forms, in turn, have the same requirements for growth as other green plants.
  • These minute forms, that constitute the primary source of food in the oceans, are restricted to a rather shallow layer of water generally no more than 450 feet (137 meters) deep [under even the most favorable conditions] called the photic zone, the zone in which there is sufficient light for plant growth.
  • The phytoplankton are consumed chiefly by their animal counterparts, the zooplankton, as well as the larvae of most of the larger forms that occupy the seas.
  • These in turn, constitute the food source for still larger animals and, in general, each form tends to feed on smaller organisms and is itself the food supply for somewhat larger organisms, the whole resting on the existence of great amounts of the simple plant forms of the phytoplankton.
  • All of the animals of the sea do not live directly on phytoplankton; many of them are carnivores, whose food is entirely animal.
  • An important intermediary is the zooplankton that preys upon the phytoplankton and in turn forms the food supply for the larger organisms.
Van Nostrand’s Scientific Encyclopedia
Edited by Douglas M. Considine
(New York: Van Nostrand Reinhold, 1989), pp. 2070-2071.

    The Oceans’s Invisible Forest

  • Every drop of water in the top 100 meters of the ocean contains thousands of free-floating, microscopic flora called phytoplankton.
  • These single-celled organisms, including diatoms and other algae, inhabit three quarters of the earth’s surface, and yet they account for less than one percent of the 600 billion metric tons of carbon contained within its photosynthetic biomass.
  • One of the most consequential activities of marine phytoplankton is their influence on climate.
  • New satellite observations and extensive oceanographic research projects are finally revealing how sensitive these organism are to changes in global temperatures, ocean circulation, and nutrient availability.
  • Phytoplankton draw nearly as much carbon dioxide out of the atmosphere and oceans through photosynthesis as do trees, grasses, and all other land plants combined.
  • Because phytoplankton direct virtually all the energy they harvest from the sun toward photosynthesis and reproduction, the entire marine population can replace itself every week.
  • In contrast, land plants must invest copious energy to build wood, leaves, and roots and take an average of twenty years to replace themselves.
  • As phytoplankton cells divide, every six days on average, half the daughter cells die or are eaten by zooplankton, miniature animals that in turn provide food for shrimp, fish, and larger carnivores.
  • Most influential to climate is the organic matter that sinks into the deep ocean before it decays.
—Falkowski, Paul G. “The Ocean’s Invisible Forest” Scientific American,
August 2002, pp. 38-45.

An individual planktonic organism.
Organisms that accumulate near the surface of water at night but live at lower levels during the day.
planktology, planktonology:
The branch of biology that studies plankton, especially as the sustenance of planktivorous fish and whales.

Plankton are demonstrating against planktivorous whales.

It is very probable that the plankton are supporters of the Japanese endeavors to kill more whales and hope that they succeed in eliminating more for their “research”! Some whales eat fish and some species of whales are equipped to eat plankton in great quantities. See information about planktonic (below) for more information about planktivorous whales.

“Japan Blames Whales for Lower Fish Catch, Claim Seeks to Defend Whale Hunting” as seen in the July 28-29, 2001 (page 2) issue of the International Herald Tribune:

  • This is Japan’s latest argument for resuming its whale hunt: Whales eat too much.
  • As part of its effort to resume commercial whaling and justify its annual catch of about 500 whales for “research”, Japan now argues that whales consume more than their share of fish; fish that should be eaten by humans.
  • Richard Mott, vice president of the World Wildlife Fund, said, “It’s undoubtedly true that whales eat tons and tons of fish, but it’s not true that every fish the whale eats is a fish humans can’t catch.”
  • Mott went on to say that whales may eat fish that prey on smaller fish, and thus keep the overall fish population higher, not lower.
  • Despite the international ban, Japan kills hundreds of whales under an exception allowing whales to be hunted for “scientific research”, though the meat is then sold for food.
  • In the European edition of Time (August 6, 2001) there was a similar article (page 21) titled: “Whale of A Fight” by Maryann Bird.

1. Those organisms that are unable to maintain their position or distribution independent of the movement of water or air masses.
2. A collective term for the wide variety of plant and animal organisms, often microscopic in size, that float or drift freely in water because they have little or no ability to determine their own movement; found worldwide in both aquatic and marine environments and representing the basic level of many feeding relationships.
3. A general term for many floating marine forms, mostly of microscopic or minute size, which are moved passively by winds, waves, tides, or currents; it includes diatoms, algae, copepods, and many protozoans, crustacea, mollusks, and worms.

Plankton refers to small animal and plant organisms that float in water and came into English as a borrowing of German Plankton, from a Greek element meaning “wandering, drifting”. The German Plankton was coined in 1887 by the German physiologist and marine biologist Viktor Hensen, 1835-1924.

  • As with the animal kingdom, the plant kingdom is divided systematically into groups and subgroups.
  • A grand division has two subkingdoms, with the more primitive being Thallophyta.
  • These include all the one-celled plants, plus related multi-celled plants in which the individual cells have comparatively little specialization.
  • The largest of these are the seaweeds which consist of undifferentiated shoots (Greek, “thallos”) and lack roots, leaves, or true stems.
  • The Greek phyton means “plant” so Thallophyta means “shoot-plants”.
  • The Thallophyta are divided into a number of phyla which in turn fall into two groups, those that include plants with chlorophyll and those which include plants with no chlorophyll.
  • The chlorophyll plants are called algae (singular, alga) which is the Latin word for seaweed, an alga that can be seen with the naked eye.
  • The non-chlorophyll plants are fungi (singular, fungus), which is the Latin word for musroom, a fungus that can be seen without the use of a microscope.
  • The plant life of the oceans belongs to the Thallophyta and it is said that it makes up about 85 per cent of all the greenery on earth.
  • The algae of the oceans manufacture their food with the aid of sunlight and so must exist only in the layers of the ocean where light can penetrate.
  • There they float, drifting with the current and serving as food, directly or indirectly, for all the animal life of the sea.
  • The algae are phytoplankton.
  • The Greek “planktos” means “wandering”, so phytoplankton are “plant-wanderers” because they must drift (“wander”) with the ocean currents.
  • Small animal life that also drifts in the currents makes up the “zooplankton”.
  • Together, phytoplankton and zooplankton are simply referred to as plankton.
  • There are also animals in the surface waters that are independent of the currents and swim as they please. These are nekton, from the Greek “nektos” (swimming).
Words of Science by Isaac Asimov
(Boston: Houghton Mifflin Company, 1959), p. 190.

Relating to, being, or characteristic of plankton.

Most whales and many fishes live entirely upon plankton, the small and nonmotile or feebly swimming organisms near the surface of the water, straining them off from the water they take in as they swim along with open mouths.

The Principles of General Biology
by Mary S. Gardiner and Sarah C. Flemister
(New York: The MacMillan Co., 1967), p. 408.

An individual planktonic organism.
planktophilous, planktophile, planktophily:
Living or thriving in plankton.
Relating to, being, or characteristic of plankton.

Diatoms represent a large share of the plankton and they provide one of the most important sources of food for aquatic animals. Certain marine animals feed almost entirely upon diatoms and the important vitamins of cod-liver and other fish oils are derived directly or indirectly from them.

The Principles of General Biology by Mary S. Gardiner and Sarah C. Flemister
(New York: The MacMillan Co., 1967), p. 128.

A planktonic plant; a member of the phytoplankton.
plantospheroidea, planktosphaeroidea:
Hemichordata (primitive worm-like animals) that up to now are only known as planktonic larvae in the form of transparent ciliated spheres.
planktotroph, planktotrophic, planktotrophy:
Feeding on plankton;
Planktonic organisms of slow-moving streams and rivers. Eupotamic plankton is confined to fresh waters and tychopotamic plankton are found in streams.
Organisms attached to drifting debris or vegetation or plankton that consists of accidental components usually not a part of the system.
Consisting of needle-shaped organisms.
Planktonic organisms associated with running water.
Plankton organisms inhabiting water rich in decaying organic matter or in foul waters. It may also consist primarily of saprophytes.
Composed largely of dinoflagellates. These are tiny single-celled marine organisms with two long slender flagella (appendages) that lie in surface grooves at right-angles to each other. Some types are luminescent and some are toxic, especially when multiplying prolifically thus causing colorful blooms; sometimes called the “red tide”.
Consisting largely of boat-shaped organisms.
Plankton that occurs below 250 fathoms.
Composed mostly of spherical forms.
Existing in stagnant water.
Planktonic organisms of freshwater bogs and marshes.
Occurring in the open ocean.
Consisting mainly of filamentous algae.
tychoplankton, tychoplanktont, tychoplanktonic:
1. Organisms occasionally carried into the plankton by chance factors such as turbulence.
2. Planktonic forms, particularly algae, that become entangled among mats of vegetation near the shore.
Another term for nanoplankton (very tiny plankton).
zooplankton, zooplankters, zooplanktonic:
Animal plankton; floating animal organisms collectively.