Illustration of the aquatic food webMicroscopic green plants called algae or "phytoplankton" form the base of the food chain for all fish.
Phytoplankton is the foundation of the aquatic food chain, the primary producers, feeding everything from microscopic, animal-like zooplankton to multi-ton whales.

Phytoplankton are the autotrophic components of the plankton community and a key factor of oceans, seas and freshwater basins ecosystems.
Chart of Phytoplakton

  • Plankton:
    Various, mostly microscopic, aquatic organisms (plants and animals) that serve as food for larger aquatic animals and fish.
  • Phytoplankton:
    Plant component of plankton.
    • Phytoplankton are primary producers (also called autotrophs). As the base of the oceanic food web, phytoplankton use chlorophyll to convert energy (from sunlight), inorganic chemicals (like nitrogen), and dissolved carbon dioxide gas into carbohydrates.
  • Zooplankton:
    Animal component of plankton
    • Zooplankton are microscopic animals that eat other plankton.
    • Some zooplankton are larval or very immature stages of larger animals, including mollusks (like snails and squid), crustaceans (like crabs and lobsters, fish, jellyfish, sea cucumbers, and seastars (these are called meroplankton).
    • Some zooplankton are single-celled animals, like foraminifera and radiolarians.
    • Other zooplankton are tiny crustaceans, like Daphnia. (If you include krill and copepods, which can swim, this group constitutes about 70 percent of all plankton)

    Zooplankton is at the base of the food chain, feeding on microscopic plants and being fed upon by aquatic insects, fish and salamanders. Their sizes usually range from one-tenth of a millimeter to four millimeters, which is smaller than the head of a pin. Zooplankton are found in freshwater reservoirs, ponds and streams. They are abundant in wetlands that often dry in the summer and fill with water in the fall.

    Because the animals are wholly aquatic but often live in habitats that dry temporarily, they are faced with problems related to the unpredictability of their watery existence. Different types of zooplankton respond to these challenges in various ways. Adult females may lay different types of eggs, depending on the season and whether the pond is likely to dry soon.

    Some eggs are resistant and do not hatch until the pond fills. Some emerge within 24 hours of the pond filling; others may take days or weeks to emerge. Some juveniles go down in the mud and rest in a protective case when the bay dries up. Some species produce resting stages when the pond dries, food supply declines or the temperature changes.

    Most zooplankton are filter feeders, using their appendages to strain bacteria and algae and other fine particles in the water. Others are predators, feeding on smaller zooplankton.

    Zooplankton can reproduce rapidly, and populations can increase by about 30 percent a day under favorable conditions. Zooplankton reach maturity quickly and live short, but productive lives. For example, adult females of a zooplankter called Daphnia can produce their body mass in eggs every two to three days. Daphnia live an average of one month.

    Researchers at the Savannah River Ecology Laboratory are studying how zooplankton respond to the extreme variability of water levels in Carolina bays. This information is being used to develop mathematical models that could predict the effects of climatic change, or global warming, on biological communities. Also, scientists are developing a computer-based model to examine how population variation is related to environmental variation and what adaptations zooplankton have that enable them to survive and leave "the best" number of offspring in different kinds of environments.

    Results from the models can be used to evaluate ecological consequences of decisions that affect the water levels of Carolina bays and similar wetlands, thus supporting the U.S. Department of Energy's land management and conservation activities on the Savannah River Site.

    If environmental factors did not regulate the population growth of zooplankton, a variety called Filinia could cover the entire world to a depth of 1 meter (3 feet) in 130 days.


    Scientists have identified more than 1,700 species. Although food, temperature and water chemistry all are important in determining what kinds of zooplankton can live in a particular lake or pond, the most important factor is predators, particularly fish. Fish prefer to eat the larger and more visible kinds of zooplankton. Thus, zooplankton that coexist with fish are typically small (less than 1 to 1.5 millimeters) and transparent.

    In contrast, zooplankton that live in ponds without fish, such as temporary ponds, often are much larger (up to 3 to 4 millimeters). Some kinds of zooplankton in fishless ponds are quite colorful: a variety called copepods can be bright orange, blue or blue with red antennae. The very largest zooplankton, called fairy and clam shrimps, live only in fishless ponds.

    Throughout the Upper Coastal Plain, three varieties of freshwater zooplankton are most common.
    They are rotifers, cladocerans and copepods. Also, fairy and clam shrimps live in ponds that dry out seasonally.

    Rotifers are called such because some species have a disc-shaped anterior end, covered with hairlike protrusions, that resembles a pair of revolving wheels. The movement is actually the synchronized beating of the hairlike protrusions, called cilia.

    Rotifers are small animals with simple body forms. They have no legs, although some have a single foot at the end of the body. Some species are protected by a shield or shell-like structure called a lorica; some have spines or paddles for protection; others live in colonies encased in a jelly-like substance.

    An organ called the mastax is unique to the digestive system of rotifers, and no comparable device is known elsewhere in the animal kingdom. It consists of a complicated arrangement of muscles that activate a set of translucent jaws used to seize, tear and grind food.

    Cladocerans, commonly called water fleas, have been favorite objects of observation by both amateur and professional biologists since the invention of the microscope. Their bodies are not clearly segmented, and many species are covered by a shell-like material. The head is a compact structure and bends downward. The most conspicuous internal structure of the head is the cladocerans' large compound eye. Cladocerans have two antennae, which help them move, and five or six pairs of lobed, leaf-like legs. Cladocerans live in nearly all types of freshwater habitats; they are most abundant in the spring.

    Adult copepods have long, cylindrical or torpedo-shaped bodies with a single eye and a pair of long antenna at the front, five pairs of legs along the middle and a paddle-like tail at the end. They use their legs for swimming. Copepods use small appendages near their mouths to capture food. Copepods lay eggs that hatch into tiny nauplii that have only three pairs of appendages. Nauplii gain legs and change form as they grow. Unlike other kinds of freshwater zooplankton, copepods also are very abundant and important in the plankton communities of the oceans.

    Fairy and clam shrimps move along the bottom or swim about and glide about gracefully in temporary ponds. They are distinctly segmented and have 10 to 71 pairs of delicate, flat, swimming and respiratory appendages.
    These zooplankton are rarely found in lakes; temporary ponds, such as Carolina bays, are one of their main habitats.


    Plankton is the first link in the marine food chain it is eaten by many organisms, including mussels, fish (Shad), birds, and mammals.

    Plankton are microscopic organisms that float freely with oceanic currents and in other bodies of water.
    Plankton is made up of tiny plants (called phytoplankton) and tiny animals (called zooplankton).
    The word plankton comes from the Greek word "planktos" which means "drifting."

    Phytoplankton is considered to be one of the most powerful foods on Earth because it is loaded with high-energy super anti-oxidants, vitamins, minerals and proteins in microscopic form. Phytoplankton is a tiny little plant (about the size of a red blood cell) that naturally grows in the ocean and is the beginning of the food chain where as all other living creatures in the ocean feed on other living things that feed on this little plant. Phytoplankton is responsible for over 70% of the planet's oxygen and because of its unique nutritional properties and microscopic size, it is believed to penetrate the cellular level of the body thereby enabling fast nutritional support to multiple health ailments.

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