All of the major phyla of animals are

represented in the plankton. Remember:

In the sea, microscopic plantlike organisms form the base of the

food chain.

This means most of the organisms that feed on these plant like organisms are

also small.

With such a wealth of microscopic food,

organisms take advantage of this rich food supply either as a larval

form or as an adult.

Some of these organisms are

herbivores feeding on the microscopic plants. Some are predaceous carnivores which feed on the herbivores or

other carnivores.

Those organisms that spend their

entire life as plankton are called

holoplankton.

Those organisms that spend part of

their life as plankton are called

meroplankton.

CopepodsCopepods are the are the most abundant most abundant of the animal of the animal plankton types. plankton types. They are They are Crustaceans that Crustaceans that feed near the feed near the base of the food base of the food chain on chain on diatoms.diatoms.

Copepods Copepods posses a single, posses a single, small small compound eye compound eye and two jointed and two jointed antennae. antennae.

Copepods Copepods also also have a larval have a larval stage that can be stage that can be very common in very common in plankton plankton samples. In Fact, samples. In Fact, many of the many of the marine marine crustaceans have crustaceans have a planktonic a planktonic Nauplius Nauplius stage.stage.

Shrimp Like PlanktonShrimp Like Plankton

Two shrimp Two shrimp like organisms like organisms are often are often found in found in plankton plankton samples… samples… Mysids Mysids and and EuphausidsEuphausids..

Shrimp Like PlanktonShrimp Like Plankton

Large swarms of Large swarms of euphausids or euphausids or KrillKrill are often are often found in nutrient found in nutrient rich cold waters. rich cold waters. There, they form There, they form an important part an important part of the food chain.of the food chain.

CladoceraCladocera

This group of This group of planktonic planktonic Crustaceans is Crustaceans is best known by best known by the the DaphniaDaphnia or water flea.or water flea.

CladoceraCladocera

Cladocera have Cladocera have a large a large anterior, anterior, compound compound eye and an eye and an enlarged enlarged carapace.carapace.

CladoceraCladocera

As can be seen As can be seen here, the female here, the female carries the carries the fertilized eggs fertilized eggs within the within the carapace.carapace.

OstracodsOstracods These These

Crustaceans Crustaceans have a large, have a large, bivalve carapace. bivalve carapace. They are often They are often nick named nick named “bean clams” or “bean clams” or “mussel shrimp”.“mussel shrimp”.

Coelenterata Coelenterata (Cnidaria)(Cnidaria)

Many forms of Many forms of coelenterates coelenterates can be found in can be found in the plankton.the plankton.

In fact, all three In fact, all three classes have classes have some some representation.representation.

Coelenterata Coelenterata (Cnidaria)(Cnidaria)

Although large, Although large, most consider most consider the the macroscopic macroscopic jellyfish to be jellyfish to be part of the part of the plankton.plankton.

Coelenterata Coelenterata (Cnidaria)(Cnidaria)

The Box jellyfish The Box jellyfish or Sea Wasp is or Sea Wasp is found off the found off the

Northern Coast of Northern Coast of Australia. It is the Australia. It is the most dangerous most dangerous

jellyfish!jellyfish!

Coelenterata Coelenterata (Cnidaria)(Cnidaria)

There are many There are many microscopic microscopic forms in the forms in the

plankton. plankton. These are These are

often juveniles often juveniles of larger of larger

organisms.organisms.

Coelenterata Coelenterata (Cnidaria)(Cnidaria)

You might also You might also find this find this Planula Planula which is the which is the larval form of larval form of members in this members in this phylum. This phylum. This example has example has been stained.been stained.

CtenophoraCtenophoraKnown as the Known as the comb jellies, comb jellies,

these these macroscopic macroscopic

organisms swim organisms swim with their 8 with their 8

cilliated rows. cilliated rows. Many, are about Many, are about

the size of a the size of a baseball.baseball.

Arrow-wormsArrow-worms

Chaetognaths or Chaetognaths or arrow-worms are arrow-worms are

often found in often found in plankton plankton

samples. About 1-samples. About 1-5 mm in size, 5 mm in size,

they are they are predaceous predaceous carnivores.carnivores.

ProtistsProtistsThere are protists that can There are protists that can be found in plankton be found in plankton samples. The three most samples. The three most common all have shells. common all have shells. Their shells are often found Their shells are often found in marine sediments.in marine sediments.

TintinnidsTintinnidsTintinnids are Tintinnids are marine protists marine protists that secrete a that secrete a vase-like shell or vase-like shell or loricalorica that protects that protects them when they them when they withdraw.They are withdraw.They are filter feeders.filter feeders.

ForaminiferaForaminiferaForams are Forams are amoeba like amoeba like

organisms that organisms that have a have a

calcareous shell. calcareous shell. These shells are These shells are very important very important

in marine in marine sediments.sediments.

RadiolariaRadiolariaRadiolarians are Radiolarians are

amoeba like amoeba like organisms with a organisms with a

skeleton formed of skeleton formed of silica. They are silica. They are

common in colder common in colder waters where there waters where there shells can dominate shells can dominate

the sediments.the sediments.

MeroplanktonMeroplankton

Remember, these are Remember, these are organisms that only organisms that only

spend part of their lives spend part of their lives in the plankton. Most in the plankton. Most become benthic or become benthic or

bottom dwelling bottom dwelling organisms as adults.organisms as adults.

Barnacle NaupliiBarnacle NaupliiBarnacles spend Barnacles spend

their adult life their adult life firmly attached to firmly attached to an object in the an object in the water. They kick water. They kick

food in their food in their mouths that’s mouths that’s

filtered out of the filtered out of the water.water.

Barnacle NaupliiBarnacle NaupliiBarnacle nauplii are Barnacle nauplii are

often common in often common in inshore samples.inshore samples.

Barnacles go from Barnacles go from this stage to a this stage to a settling cypris settling cypris

stage and then to stage and then to the sessile adult the sessile adult

stage.stage.

Veliger LarvaeVeliger LarvaeMollusks have Mollusks have

several planktonic several planktonic stages. They have stages. They have

a ball like a ball like trochophore stage trochophore stage

and a veliger and a veliger stage.stage.

Veliger LarvaeVeliger Larvae

Often, you can Often, you can find the shells of find the shells of these immature these immature

mollusks in mollusks in plankton plankton samples. samples.

ZoeaZoea Crabs, like many Crabs, like many

Crustaceans Crustaceans have a larval have a larval

stage known as stage known as a zoea. At a zoea. At

certain times of certain times of the year it can the year it can dominate the dominate the

samples!samples!

MegalopaMegalopa The megalopa The megalopa

stage stage resembles the resembles the adult and will adult and will soon settle to soon settle to the bottom.the bottom.

Echinoderm LarvaeEchinoderm Larvae

Echinoderms have Echinoderms have a bilateral larval a bilateral larval stage that can stage that can

often be found in often be found in near shore near shore samples of samples of plankton.plankton.

Fish LarvaeFish Larvae

Larval fish are Larval fish are often part of often part of the plankton.the plankton.

Fish EggsFish Eggs

Even fish Even fish eggs can be eggs can be found in the found in the

plankton plankton samples.samples.