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