Marine
Education
Trust
Student Sheet: RL-2
Write a key to marine invertebrates
There are hundreds of different species in the lagoon and on the reef and although some biologists
are very good nobody knows what everything is called. To help us identify plants and animals we
can use pictures but sometimes this isn’t enough. Biologists use keys, a series of yes or no
questions, to help them identify organisms they don’t recognise.
Here is a simple key for telling the difference between some different molluscs.
Key to different kinds of molluscs
1.
2.
3.
Does it have a hard shell on the outside?
Yes
Go to question 2.
No
Go to question 3.
Is the shell made in one piece?
Yes
It is a snail.
No (two pieces)
It is a bivalve.
Does it have long tentacles and large eyes?
Yes
It is a cephalopod
No
It is a sea slug
Try the key out on these molluscs!
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Now write your own key to some of your favourite lagoon creatures!
© Marine Education Trust 2010 – All commercial rights reserved
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Marine
Education
Trust
Student Sheet: RL-3
Lagoon food chains and webs
Plants use the chemical process called photosynthesis make their own food using water, carbon
dioxide and sunlight energy.
Because they make food, plants are called producers. Animals need food too, but they cannot make
their own so they must eat other organisms to obtain it. They use of some of the food to give them
energy to live. If they eat more food than they use up, animals grow and get bigger. This means
someone else can now eat them…!
If plants are producers then animals are consumers. Consumers may eat plants (they are
herbivores), or eat other animals who eat plants (carnivores), or eat other animals who eat other
animals who eat plants, and so on as part of a food chain.
Single celled alga
(producer)
Coral
(primary consumer)
Butterflyfish
(secondary consumer)
Reef shark
(tertiary consumer)
Each consumer will often eat lots of different things, so an ecosystem will have many different food
chains which together form a food web.
Big food web wall project
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Find out about one lagoon animal and what it eats. Make a big, colourful picture of it.
Put all of your pictures up on a wall and add big arrows to show who eats who.
Put the producers at the bottom and the big carnivores at the top.
© Marine Education Trust 2010 – All commercial rights reserved
Student Sheet: RL-4
Marine
Education
Trust
Marine plants and photosynthesis
Algae, or seaweeds, are simple plant-like organisms which are only found in water. Sea grasses are
different from algae, they are closely related to land plants. Both algae and sea grasses are
producers, that is they are organisms which actually make food in an ecosystem, in the process we
call photosynthesis.
In photosynthesis, plants use light energy from the sun to make sugar from water and carbon
dioxide gas. Oxygen is produced as a waste product.
The sugar produced provides food for the plant, for herbivores who eat the plant and for carnivores
who eat the herbivores. If it wasn’t for photosynthetic algae there could be no life in the lagoon!
An experiment to show photosynthesis by algae
What you need
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Two empty clear plastic drinks bottles
Seawater
A long drinking straw
Freshly collected marine algae or sea grass
A few drops of bicarbonate indicator solution
What to do
1. Bicarbonate indicator is a substance which is yellow when carbon dioxide is
present and red or purple if there is no carbon dioxide.
2. Measure a litre of seawater into each bottle.
3. Add the same volume of bicarbonate indicator to each bottle. It should appear pink.
4. Blow bubbles in the bottles using the straw. The carbon dioxide in your breath should dissolve
and turn the indicator yellow.
5. Put some algae in one of the bottles and screw on the caps.
6. Place both the bottles in the sun and watch what happens!
Things to think about
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Can you explain the difference between the two bottles?
What happens to a bottle in the shade?
What would happen if you put a few small sea snails in the bottle?
What other experiments can you think of? Carry some of them out!
© Marine Education Trust 2010 – All commercial rights reserved
Marine
Education
Trust
Student Sheet: RL-5
Pollution in the lagoon
Pollution is the introduction of objects or substances
into the environment that causes harm to ecosystems.
Pollution includes things you can see (like plastic
waste) and things you can’t (like chemicals or sewage).
Lagoons are particularly vulnerable to pollution
because they are enclosed and the substances can
become trapped. Objects like plastic bottles can pile
up on the beach in some places and the concentration
of dissolved substances can build up over time.
Plastic waste on a beach in Hawaii. Image by Polihale.
Pollution beach walk
Mark out a strip of beach 100m long.
Pick up all of the plastic waste you can find and dispose of it properly
Separate out the bottles and count them. Keep some for doing experiments
Once a week, go back to your area of beach and count the number of new bottles. Make a wall
chart that shows what you find each week
• Make a poster encouraging people to dispose of waste properly
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© Marine Education Trust 2010 – All commercial rights reserved
Marine
Education
Trust
Student Sheet: RL-6
How long does pollution last?
Some materials will break down naturally over time,
often due to decomposition by invisible bacteria. We
call such materials biodegradable. Other materials,
particularly if they are man-made, do not break down
easily and may stay in the environment for a long time.
Plastics can be a big problem, although scientists have
now made some which are biodegradable.
Plastic waste on the beach at Dar es Salaam.
Photo by Loranchet
Make a biodegradometer
• Collect up some different kinds of waste from the beach, e.g. plastic bottles, chip packets,
polystyrene cups, cardboard or banana peel.
• Pin them to a big board outside
• Check back to see how quickly they break down – it could take a long time!
Things to think about
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Where does your rubbish go when you throw it away?
What sort of materials can be recycled?
How many plastic bottles does your family throw away each week?
What is plastic made from?
© Marine Education Trust 2010 – All commercial rights reserved
Marine
Education
Trust
Student Sheet: RL-7
Pollution and algal blooms
When some substances enter the water in the lagoon
they may simply poison and kill all of the organisms, but
this isn’t always the case. Some substances are very rich
in important nutrients and can cause very rapid growth
of algae, especially phytoplankton.
Two important sources of nutrient pollution are sewage
and fertilisers used in agriculture. Both of these things
have the same effect. Normal seawater is very low in
nutrients, so algae only grow very slowly. If sewage or
fertilisers are washed into the lagoon the algae may
suddenly grow very quickly and turn the water reddish
brown (a “red tide”) or green. This is called an “algal
bloom”. The algae make the water very murky, blocking
out light, and may even be poisonous and kill fish.
This bloom is so bad it is visible from space!
Make your own algal bloom!
What you need
• Two empty clear plastic drinks bottles (you should have some from the beach!)
• Fresh seawater
• Plant food or fertiliser
What to do
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Measure a litre of fresh seawater into each bottle
Add 10ml of plant food or fertiliser solution to one bottle
Cap both bottles and stand in a sunny spot
Record the appearance of each bottle every day for a week
Things to think about
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Find out why algal blooms are a bad thing
Can you explain what has happened in the bottle with the plant food?
What does this tell you about ordinary seawater?
Why is tropical ocean water so clear when coastal waters are more cloudy?
How can we reduce how much pollution enters our lagoons?
© Marine Education Trust 2010 – All commercial rights reserved
Marine
Education
Trust
Student Sheet: RL-8
Reef and lagoon quiz
1.
What does echinoderm mean? .........……..…………………………………………………………………………………………
2.
Sea stars are one kind of echinoderm, can you name another? ...........……………………………………………..
3.
What group do crayfish and crabs belong to? ............………………………………………………………………………
4.
Is coral an animal, a plant or a rock? .................………………………………………………………………………………..
5.
What do we call the process in which plants make food using sunlight? ............……….………………………
6.
If all plants are producers, what are all animals? ..........……………………………………………………………………..
7.
If you ate a big fish that ate 100 little fish and each little fish ate 100 tiny fish, how many tiny
fish died to feed you? ......................................................................................…………………………………..
8.
What do we call it when algae grow suddenly in the lagoon? .................…………………………………………..
9.
What word describes materials that can be naturally broken down by bacteria? ............................…..
10. The lagoon is a fun, fascinating place but can also be dangerous. What precautions should you
take before you go there? Write down as many as you can (use the back of the sheet if you
need to!)
© Marine Education Trust 2010 – All commercial rights reserved