« Plankton of the World »
`` To raise students’ awareness about marine
plankton diversity
Plankton: definition and collection
`` To understand the major role of plankton in
marine ecosystems
Definition
`` To establish and describe various food webs,
`` To introduce the students to an ‘investigative’
approach
`` To encourage and
observational skills
develop
students
`` To exchange with other European classes
involved in the network
« Plankton of the World » (1)
© Océanopolis / T. Joyeux
« Plankton of the World » has been organised by
Océanopolis and Agrocampus Rennes (Beg-Meil
venue) under the framework of the World Ocean
Day annually on 8th June for the past 3 years. Since
2007, in collaboration with EUR-OCEANS (a
European Network of Excellence), the following
objectives have been developed :
Various aquariums of the EUR-OCEANS network
offer teaching workshops to teachers and students
on the topic of plankton.
On completion of their study, students are asked to
produce a presentation, which will be displayed in
each aquarium and could be done in a range of
formats :
In sea water, some algae and animals float, they
have limited ability to control their movements and
so drift with the currents. These algae and animals
are known as plankton.
Where and how to collect plankton ?
You can collect plankton on the seaside or off the
coast, depending on the location. In order to collect
plankton you will need the following tools :
``
``
``
``
``
``
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1 plankton net
2 or 3 sieves: PVC tubes with a mesh between
20 and 150 microns
1 pipette
2 or 3 glass slides
2 or 3 coverglasses
a microscope
`` A plankton history,
`` A dancing or theatre show,
`` Drawings, etc
In order to help teachers work on this topic with
their students, several educational sheets have
been produced.
Protocol
`` At the seaside
- Step 1 : Plankton is collected by drawing the
plankton net through the water (for 1 to 2 minutes).
The plankton net has a small bottle attached to
the end, when it is dragged through the water the
organisms are collected and filter straight into the
bottle.
Be careful! Plankton organisms do not survive
for more than a few hours. You have to take the
bottle back to the classroom quickly in order to
observe the plankton. Alternatively, you can work
on samples kept in 5% formaldehyde.
Some microscopic algae
`` In the classroom
Cyanobacteria
Spiruline
Tamis (PVC tube with a mesh
between 20 and 150 microns)
© Hélène Laguerre / Cempama
Pipette
Cristallizing dish
Diatom
Naviculacea
South of Brittany
- Step 2 : Take a sieve, put it over a crystallizing
dish containing sea water, incline the seive slightly
and pour ¼ of the bottle on the sieve, so that the
various species of plankton will accumulate in one
corner of the sieve.
© Aude PIRAUD / Association
Plankton observatory
- Step 3 : Take some water containing the plankton
from one corner of the sieve with a pipette, and put
a few drops on to a glass slide.
Spiruline
Warm waters culture
- Step 4 : Cover the drops with a coverglass, and if
necessary add a drop of 5% formol.
© T.Joyeux / OCEANOPOLIS
- Step 5 : Observe the plankton through the
microscope.
Phytoplankton
« Plankton of the World » (2)
Definition
Phytoplankton is the marine equivalent to plants
on the land. It is composed of 6,000 species of
microscopic algae, whose size ranges from 1 micron
to 1 mm. It is the most numerous group of marine
plants. As any plant, phytoplankton converts CO2
and sea-water into oxygen and carbohydrates
through a process known as photosynthesis.
Because this process strongly depends on solar
energy, it can only happen in the surface layer of
the ocean, where light is sufficiently abundant.
These microscopic algae form (with macro-algae)
the first link of food webs in marine environments,
i.e. they are eaten by microscopic animals
(zooplankton) or larger marine organisms (e.g.
mussels).
Example :
Microscopic algae (phytoplankton)
are eaten by
Herbivorous zooplankton
Microscopic algae (phytoplankton)
are eaten by
Mussels
b) Temporary plankton
Zooplankton
Definition
Larve a of sea urch
in Iroise sea
Zooplankton are a group of animals that drift with
currents. It includes both permanent zooplankton,
i.e. organisms which are born, live and die as
zooplankton, and temporary zooplankton, i.e.
organisms which spend only part of their lives,
generally the larval part, as zooplankton. The
latter goes through a metamorphosis at a given
stage of its life and turns into a very different
animal. In order to do this the animal must stop
floating and attach itself to a rock.
© T.Joyeux / OCEANOPOLIS
Jellyfish
Aurelia aurita
British Channel
© T.Joyeux / OCEANOPOLIS
Some species of animal plankton
Links of the food web
a) Permanent plankton
To live and grow, both, permanent and temporary
zooplankton need :
« Plankton of the World » (3)
Nauplies of Artemia
Salins du midi
(France)
© T.Joyeux / OCEANOPOLIS
Copepodes
Tatihou island
(France)
© T.Joyeux / OCEANOPOLIS
`` either phytoplankton,
(herbivorous zooplankton),
`` or smaller zooplankton,
(carnivorous zooplankton).
Phytoplankton
is eaten by
Zooplankton
is eaten by
Barnacles
Mussels
The shorter a food web is, the more productive it is.
One can say that : 1,000 kg of microscopic algae
produce 100 kg of mussels, which produce 10 kg of
sea breams, which produce 1 kg of seal.
The food web
Marine organisms can be classified according to
the origin of their food:
`` Primary producers (phytoplankton and macroalgae) use light and mineral elements to
produce their own biological tissues.
To summarize :
`` Phytoplankton (a primary producer) is eaten
by herbivorous zooplankton (protozoa and
copepods), which in turn is eaten by carnivorous
zooplankton (e.g. shellfish larvae).
`` Primary consumers (zooplankton, sponges,
mussels, ascidians …) these herbivores eat
other primary producers, they filter sea
water to collect the phytoplankton. They are
herbivorous.
`` Marine plankton are thus a key link in marine
trophic networks, being a source of food for
small corals but also for fish and for the giant
whale shark, or the whale itself, the biggest
mammal.
`` Secondary consumers (cuttlefish, octopus,
sea stars, small fish) eat herbivores. They are
predators or carnivores.
`` Super-predators such as seals are at the top
of the food web, they are the last link in the
chain.
With your students, use the poster “Trophic relations
in the marine environment” to produce an example
of trophic network.
Carcasses and other organic detritus are consumed
by decomposer organisms, bacteria. Bacteria
transform organic matter mineral elements witch
re-enter the water column and are then used once
again by the phytoplankton.
Do not forget to place the arrow between two links
in the following direction :
is eaten by
It is also important to show the key place of these
organisms within marine food web networks. What
would happen to the food web if phytoplankton
and zooplankton disappeared?
© Océanopolis / T. Joyeux
« Plankton of the World » (4)
A food web or network is a collection of several
food chains. One animal can thrive on various
sources of food, and can also be the prey of
several different animals.