32
91 Vegetation Field Work
91
VegetationField Work
92
Algal Pressings
Level3-8+
Key questionHow are marine algapressed?
Key outcome Identify features of algaethat determine theirclassification.
What you needClipboardPaper, pencilPetri dish or flat platePaintbrushAbsorbent paperNewspaperGlueHeavy bookField guide to seaweeds
What you do
There are many varieties of algae including those calledseaweed. Try to collect different ones in small quantities.
1. Collect as many types of algae as possible. Place each ina dish filled with water and use a small paintbrush tospread the algae out.
2. Carefully lift the algae onto a sheet of absorbent drawingpaper and use the paint brush to spread it out again. Theeasiest way to do this is to slide a piece of paper into thewater under the seaweed and raise the paper slowly,allowing the water to drain off. Place another sheet ofpaper on top of the algae.
3. Press the algae by placing the paper wrapped innewspaper and place a heavy weight on top or use aplant press. An old telephone book makes a good press.Allow this to stand for at least a week. When dried, usecraft glue to stick the algae to the paper.
4. Use text books to find out the scientific name of thealgae. Write this on the sheet of paper along with thedate the pressing was done.
Adapted from ReefEd, a n d
Moroney et al., C o a s t a l
Activities for Primary Schools .
Algal Pressings
Extensions
Devise methods of grouping the different types of algae.
Use the algae to create unique cards and writing paper.
Press other plants.
References Christianson, I.G., Clayton, M.N. and Allender, B.M. (eds.) 1981, Seaweeds of Australia, Reed Pty Ltd,New Zealand. Cribb, A.B. 1996, Seaweeds of Queensland: A Naturalist’s Guide, Queensland Naturalists’Club. (Availablefrom QNC, Dept. Anatomical Sciences, University of Qld 4072 for $15 and $3 postage.)Hughes, J.M.R. and Davis, G.L. 1989, Aquatic Plants of Tasmania, University of Melbourne Press, Dept.Geography.
93
94
Identifying Algae
Level7-8+
Key questionsHow do we use a key tofind out about algae?
Key outcome Identify the features ofalgae that determine theirclassification into majorgroups.
What you needSuitable seashore with variety of algaeKey sheetsField guide to algae/seaweedsMagnifying glasses
What you do
Take care while doing this activity that you do not slip onrocks covered in algae. Don’t pick up a large clump ofseaweed on the beach without shaking it first to dislodge anystinging jellyfish, syringes, or glass. As this key has beendeveloped for temperate and sub-tropical Australian shores, itmay not contain all tropical algae.
Work in small groups or pairs to locate algae. Some may beon rocks and in crevices; others may be floating in the sea, orwashed up on the beach at the high tide mark. It is notnecessary to always pick individual alga (the singular ofalgae).
Biological keys rely on a logical procedure to review certaincharacteristics and eliminate some which do not relate to onespecies. Work through the keys provided and name yoursample specimens.
Consider your data: how many different algae did you find?Where were most located? Which was the smallest one?Which was the largest? Which is the dominant colour? Arethere any algae which you could not key out and identify?
Extensions
You could do the ‘Algal Pressing’ activity, and the ‘Red AlgaeBloom’. The latter looks at a problem associated with therebeing too much of one type of alga.
Undertake research into the consumers of algae.
Key used with permission
from Moroney, D., Bourke, S.
and Hanson, S., 1994, Caring
for the Coast: Coastal
Activities for Primary
Schools, City of Henley and
Grange, Henley Beach, SA.
95
Identifying Algae Key
The Green Algae – Phylum Chlorophyta
The green algae are the most common kind of freshwateralgae and they are common at sea, especially in shallowwater.
Key to some Green Algae
1a. Plants consisting of single filaments of large cells, un-branched .....................Chaetomorpha
1b. Plants consisting of single filamentsof large cells, branched ...............................Cladophora
1c Plants not as above.......................................................2
2a. Plants pale green, thallus (body) athin sheet or a hollow tube...........................................3
2b. Plants darker green, Thallus complex,not a flat sheet or hollow tube.......................................4
3a. Thallus a thin sheet of bright green cells, two cells thick................................................Ulva
3b. Thallus a thick sheet of dull green cells ......................................Dictyosphaeria
3c. Thallus a thin-walled, hollow tube:often branched near base, tube sometimes flattened ................................Enteromorpha
4a. Plants with erect branches (fromhorizontal stolons) branches with many protrusions called ramuli; ramulican be fine and pointed or vesicular ...............Caulerpa
4b. Plants with erect branches (without stolons); branches with many ramuli; ramuli fine, slender with rounded ends ............Bryopsis
4c. Plants erect and branched, or almost globular or appressed to rocks, consisting of the fine interwoven filaments ending in small swollen ‘bulbs’ on the surface ...........................Codium
Chaetomorpha(Mermaid’s necklace)
Ulva(sea lettuce)
Dictyosphaeria
Identifying Algae Key
96
The Blue-Green Algae – Phylum Cyanophyta
Blue-Green Algae are very primitive plants. Several species arecommon in the inter-tidal and sub-tidal zones in SouthAustralia.
Key to Two Blue-Green Algae
1a. Forming a thin black film on a rock, or epiphitic and slimy when wet, supralittoral.....Calothrix
1b. Forming small or round or irregular blobs on rocks or epiphytic, 1-2 cm across, blue-green in colour, gelatinous.......................Rivularia
The Brown Algae – Phylum Phaeophyta
The brown algae are usually the most conspicuous plants in thesublittoral and sub-tidal zones in South Australia. The commonones are large, tough plants growing attached to rocks andreefs.
Key to some Brown Algae
1a. Plants with hollow bladders on some part of the thallus...........................................................2
1b. Plants without bladders..................................................5
2a. Plants consisting of branched chains of hollow bladders ..............................................Hormosira
2b. Plants with stems and leaf like structures as well as bladders.........................................................3
3a. Plants large, 1-10 m long, bladders (1.5–3 cm across) at the base of large flat blades (leaf like structure)......................Macrocystis
3b. Plants usually less than 1 m tall, bladders small (3-8 mm), bladders not forming a part of the blade............................................4
4a. Main axis with sympodial (zigzag)branching, the small ends of the branches
(ramuli) usually long and thin.......................Cystophora
Cystophora (About 25 species)
Calothrix
Rivularia
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Identifying Algae Key
4b. Main axis without sympodial branching, ramuli sometimes long and thin, sometimes broad and flat like a leaf (often both sorts on the same plant).............. Sargassum
5a. Stems long and thin (pencil thickness), rough and warty, no leaf-like blades................. Scaberia
5b. Plants consist of large holdfast (organ for attachment), and thick stems ending in large flat blades...............................................6
6a. Plants small, usually less than 1 m high, blades with an uneven surface.......Ecklonia radiata
6b. Plants large, 1.5-8 m long, blades thick and smooth with numerous long divisions....................................Durvillea
The Red Algae – Phylum Rhodophyta
This group has the largest number of species. There is a greatdiversity in their structure and reproduction making theirtaxonomy very difficult. Many of the reds are deep waterspecies and so are not often seen on reefs. Some of thosecommonly found on reefs secrete calcium carbonate(limestone) making them rock hard. These have the commonname of coralline algae. Usually they are pale pink in colourbut may appear white if bleached by the sun. They arecommonly mistaken for corals.
Key to some Coralline Red Algae
1a. Branching dichotomous (dividing exactly in two at each branch)..................................Jania
1b. Branching pinnate (feather-like)........................Corallina
1c. Branching in irregular whorls.................Metagoniolithon
From Below High Water Smith, J.H., John, E.W. Education Dept. of SouthAustralia, 1979.
Sargassum
(About 25 species)
Scaberia
Ecklonia radiata (Kelp)
98
Identifying Algae Key
Hormosira (Sea Grapes)
Macrocystis
Jania Corallina
Durvillea (Bull Kelp)
EnteromorphaByropsis
Caulerpa(About 20 species)
Codium (About 15 species)
99
Herbarium Specimen Preparation
Level4
Key questionHow should plant samplesbe prepared for lateridentification by aherbarium or for display?
Key outcomeIdentify features of plantsthat determine theirclassification into majorgroups.
When collecting plant materials, enough information must berecorded to permit classification of the specimen accurately.Reproductive structures are important in classifying plantspecies. The pieces collected must be typical of all plants ofthat species in the area.
What you needAbsorbent paper, for example, paper towelsA4 envelopes or plastic bags to hold specimensSticky labels to mark bagsPlants to study (seaweeds or terrestrial)Pen, paper
What you do
You can work in small groups to cover a dune or coastalforested area (don’t rip the plant out by the roots or breakwhole branches off). Collect for each plant:
• flowers seed pods, capsules, fruits
• leaves (attached to stems so that you can identifywhether arrangement is opposite or alternate)
• bark, if possible.
Record in the field on paper or sticky label:
• the locality
• type of environment
• the habit (vine, herb, tree, shrub)
• other special features.
Press immediately.
In the field, place the specimens between pieces of absorbentpaper and slide into an envelope in a folder for safe-keeping.Seed pods, fruits etc. may be kept separately but must benamed appropriately so they can later be re-united accurately.
Adapted from Field notes for
Stradbroke Island, Rochedale
High School, Brisbane.
100
Take note to:
• Avoid collecting on a wet day or after heavy dew. Get the driest sample possible.
• Press evenly and flat.
• Place leaves up the same way.
• Press flowers so petals may be seen for shape, number, arrangement.
• Label envelope or bag.
Drying specimens
Most specimens need to be pressed between several layers of paper (e.g. newspaper)
under a heavy weight for two or three weeks, or use a plant press. Change paper after two
weeks. If plants are wet, they may go mouldy and will have to be discarded. Keep labels
with plants. Old telephone books make convenient size plant presses.
If plants cannot be identified, the pressed specimens should be spot-glued onto white A4
stiff paper or cartridge paper, labelled with locality, habitat and date and forwarded to the
herbarium (in each capital city) for identification. There may be an identification charge if
you have many samples, though small numbers may be free.
After pressing, the specimens can be mounted on card in a folder to serve as a local field
guide (see Figure 1). They can be stored in plastic sleeves in folders (with their labels).
Remember!
Plants are precious! DO NOT DESTROY any plants. Collect material with great care soas not to damage the specimen.
Herbarium Specimen Preparation
101
Herbarium Specimen Preparation
Figure 1. An example of a herbarium specimen which shows you how to mount yourspecimen and display information about it
branch
leaves
flower
Phylum: Tracheophyta
Class: Angiospermopsida
Family: Myrtaceae
Genus: Callistermon
Species: viminalis
Habitat: Dry sclerophyllforest
Location: Rochedale
Notes: Found at the edgeof the forest.
Date: May, 1987
Collector: E.X.Ample
seed cases
102
Comparing Different Plant Communities
Level7-8
Key questionsWhat do you notice aboutthe different plantcommunities?Can you explain why someof the factors differ fromeach other?Are there other factorswhich could be used tocompare vegetation?
Key outcomesRecord observations aboutdifferent plant communities(e.g. dune, estuary, up-stream).Define why/how plantcommunities differ.
This activity provides an alternative approach to surveying
different communities of vegetation and does not require
transects or quadrat studies. As such, the method is more
appropriate for obtaining data for quick comparisons (such as
those required for the ‘Bird Diversity Indices’) or when the
vegetation community is too fragile or valuable to allow a
class group of students to tramp through it, or when time is
short.
What you need
Light or exposure meter
Field sheet, pencil
What you do
Students should be divided into small groups or pairs, and
issued with equipment. They then complete the field sheets,
choosing at least two different habitats or communities.Adapted from field sheets
from Rochedale High School,
Brisbane, Royal National Park
Field Studies Centre, Sydney,
and Griffith University,
Brisbane.
Available Light
Using a light meter or exposure meter devise a five point scale (equivalent to ASA 64
film) where these combine, for example:
Full sun Hazy sun & Weak sun Shady but Open shade
distinct shadow & soft shadow bright, no shadow to full darkness
f16 f11 f8 f5.6 f4
(Number equivalents equivalent to ASA 64 film)
5+ 4+ 3+ 2+ 1+
Wind Exposure
Continual Show signs of Affected Wind present Completely
exposure adaptation during storms, but not sheltered
to wind etc important
5+ 4+ 3+ 2+ 1+
Comments can be made concerning reasons for the degree of exposure to wind.
Depth of Soil
Very shallow Shallow Some depth Deep Very deep
0-0.5 m 0.5-2 m 2-5 m 5-10 m 10m +
Comments could be made about the amount of ‘topsoil’ in any of the above
103
Comparing Different Plant Communities
Field sheet 1
Type of soilSoil could be described on a one to five scale according to how coarse it feels.Very coarse) Holds together Easily worked More slippery Very slipperyand gritty but still gritty good’ soil than gritty and fine(sand) (sandy-loam) (loam) (clay-loam) (clay)5 4 3 2 1
Water in soilSoil Soil holds Soil wet Soil only Soilconstantly water for enough for wet constantlywet long period good plant immediately dry(swamp) after rain growth after rain (sand dune)5 4 3 2 1
Type of vegetationThis can be expressed as the percentage in an area, say, 10 metres by 10 metres.Trees Shrubs Herbs Grasses Other(%) (%) (%) (%) (%)
The comparative height of the vegetation can be shown by using diagrams which show a‘profile’of the vegetation compared to the height of a person.Type of leafThis can be expressed as the percentage in a given area.Small Small & prickly Hard &grey green - Soft & dark green Other (%)(%) (%) (%) (%)
Ground coverThis can be expressed as the percentage in a given area.Fully covered Intermittent Leaf litter Plant Barewith plants spaces & complete only only ground& leaves coverage (%) (%) (%) (%) (%)
CanopyThis can be expressed as the percentage in a given area.Full canopy Fairly complete Half canopy Sparse canopy No canopy(%) (%) (%) (%) (%)
Type of animalThis can be expressed as a percentage after calculating the total number in each group.Insects Amphibian Reptiles Birds Mammalsinclude otherAnthropods(%) (%) (%) (%) (%)
Comparing Different Plant Communities
Field sheet 2
105
Growing Mangroves
Level3-8
Key questionHow can mangroves beraised from seed?
Key outcomeTo review the growth anddevelopment ofmangroves.
You may be able to grow a mangrove from seed so long as theseed is not collected from a national park or marine park, orfrom Queensland, (where all mangroves and their seeds areprotected). Educational centres may be able to obtain a permitin Queensland particularly if the centre has a shade house.
What you needSpadeSeed raising mixPlant potSeed pods or seedlings of mangroves
What you do
Seedlings of mangroves are produced while they are still onthe parent tree. Avicennia marina (grey mangrove), the mostwidespread mangrove found in both tropical and temperateAustralia, can hold onto seedlings until they are some 30 cmlong. This process is called viviparity. Seedlings may drop offthe tree, float in the water and then settle in fine mud. Or,some may be picked from the tree.
Seedlings can be dug up and replanted into a plant pot in fin e ,silty mud. Or, seeds of grey and other mangroves can be placedin a seed raising mix in a plant pot. The seedlings can be wateredwith freshwater (or left in the rain), and once a week, need awater with salt water. This should preferably come from the sea,but you can mix your own by dissolving two teaspoonfuls oftable salt in a litre of water. If you place the plant pot in a bucketof semi-salt water, the mangrove seedling is more likely todevelop aerial roots (pneumatophores) after at least six months.
The plants can be examined for salt crystals coming throughthe salt glands on the surface of leaves.
If the seedling is removed from the silt in the pot and carefullyrinsed, the fine network of feeding roots can be observed.
Extension
The seedling can eventually be replanted in a mangrove forest.
In areas where collection of mangroves is not permitted,students can locate a suitable seedling, tag it using plasticribbon and regularly visit it to observe and record growth. Itcan be watched for salt crystal development. The fullflowering cycle may also be observed in the field.
ReferenceClaridge, D. and Burnett, J. 1993, Mangroves in Focus, WetpaperPublications, Ashmore.
Adapted from Edfish, DPI,
Queensland, and from field
notes of the Department of
Education, Northern Territory.
106
Mangrove Fieldwork
Level4-8
Key questionWhy are mangrovesimportant?
Key outcomeIdentify and describemangrove species and theirenvironment.
What you needField sheets (with key) on clipboardPencil
What you do
These activities are chiefly used in Queensland, NorthernTerritory and North Western Australia, where there are morethan one species of mangrove. However, they can be useful insouthern temperate mangrove areas, even if the GreyMangrove is the only species available.
Students can work in small groups or pairs. Ensure you arefamiliar with hazards such as watching for the tide to come in,avoid stepping in soft mud, and not handling broken glass. InQueensland, all mangroves and their leaves, seeds and litterare protected unless the teacher-in-charge has an educationalcollecting permit. All states regulate the collection of plantmaterial in marine or national parks.
Walk around a mangrove area, and complete the followingquestionnaire.
Question Yes No Undecided
1. All mangrove trees are the same
2. All mangrove areas are smelly
3. Artificial waterways (canals) are
the same as natural ones
4. Tidal wetlands are important
to bird and fish life
5. Mangrove roots collect sediment
and stabilize waterway banks
6. Wetland areas are very rich
in nutrient
7. There are laws to prevent
mangrove clearing
8. Mangroves have to be cleared
before you can build canal estates
9. Mosquitoes and sandflies only
breed in mangrove areas
10. We should be more concerned
about wetland areas
These activities are a
combination of several field
trips to mangroves, some used
during Seaweek 1996; many
ideas were contributed in the
Jervis Bay workshop of Mike
Michie, Department of
Education, Northern Territory.
Questionnaire derived from
Claridge & Burnett (1993).
Which mangrove is it?
Use the key (& also the accompanying ID & treasure hunt sheets).
Leaf comparisonsFind some different mangrove types and compare their leaves. What is the biggest leaf on amangrove tree? The smallest?Are leaves succulent, or shiny, or waxy in feel? Do they have hairs? Is this a sticky milky sap (donot touch the sap)? Would any of these features help the plant survive in salty mud and hightemperatures?
ReproductionWhat ways do mangroves have of reproducing? Can you find seeds and young plants? How didthe seedling develop?
Other vegetationWhat vegetation lives behind the mangroves on the inland side? Would these plants have salttolerance too? What adaptations to the conditions can you see? Use the information sheet to assist.
While you walkList the valuable things provided at this spot – nature’s assets. Which of them could causeproblems? Which are likely to be altered and lose their value with human influence?
BirdsCan you identify the birds you see or hear? Are they feeding in the mud? What would they eat?Are they sheltering in the mangroves? Would birds in wetlands like these need special features tohelp them live here? Use the bird pictures to help.
My sensesShut your eyes and listen and smell for two minutes. Which sounds dominate? Which smellsdominate? Which do you dislike?
Mini trailPretend you are an ant in this area. Use your eyes or a magnifying glass to follow a short trail-what do you notice?
I spyThe group is divided into couples, who then wonder along shore or mud flats. Meet back at acentral point. Each individual finds one natural item (animal, vegetable or mineral), and thendescribes it without stating what it is to the partner. You need to include some habitat description,some indication of major features (e.g. does it have a shell, is it moving, can it move, whatcolour). The partner has to locate the item and attempt an identification.
107
Mangrove Fieldwork
109
Mangrove Fieldwork
Plants fringing the mangroves
Cottonwood Hibiscus (Hibiscus tiliaceus)
This rounded-leaf dense shrub or small tree is common an thelandward side of the mangroves often being found near theOrange Mangrove. The Aboriginal people actually told a storyexplaining the imagined relationship between the two plants.The cottonwood’s leathery leaves are wind and salt resistant,enabling them to colonise areas close to the beach. The largeyellow flowers open early morning, turning orange by aboutmidday and closing by mid afternoon.
Aborigines had many uses for the tree. Young leaf shoots,flower buds and roots were eaten raw or after cooking. Thebark was stripped off and sucked. This bark was also highlyfavoured for its strong fibre to make rope and thread. Firesticks were also made from the wood at times.
Swamp Oak (Casuarina glauca)
A tall fir-like tree often found close to mangrove trees but notas tolerant of salt water. The word Casuarina comes from thebird Cassowary and refers to the stringy leaves which looklike the straggly feathers of the Cassowary of NorthQueensland.
The Swamp Oak has no true leaves. The narrow twiggy‘leaves’ are actually stems. The leaves are almost microscopicand have been almost lost through millions of years ofevolution. This adaptation stops the trees losing water throughthe leaves by dehydration by the sun. Plants of salty coastalareas need to retain as much moisture as possible to keep saltconcentration within plant tissue low.
Casuarinas have the ability to put nitrogen back into the soil.Attached to their roots are microscopic fungi which formnodules (small lumps). These fungi produce nitrogen for theplant to use to grow, and also for the surrounding soils.
Cottonwood Hibiscus leafyshoot
CottonwoodHibiscus flower
Cottonwood Hibiscusfruits
Swamp OakLeafRemnant
Mangrove Fieldwork
112
Crested Tern
Silver Gull
MangroveHoneyeater
Rainbow-beeCatcher
Pled Cormorant
Pled OysterCatcher
Great Egret
Australian Gannet
White-cheekedHoneyeater
Sacred Ibis
Birds of the wetlands
113
The Mangrove Ecosystem
Level5
Key questionsDo algae and organicdetritus form the basis ofmangrove food chains?What do herbivores andcarnivores eat in amangrove community?What are the other rolesplayed by mangroves?Are different groups ofanimals found in themangroves at various timesas the tide and seasonchanges?
Key outcomesRecognise the importanceof mangroves in a marinesystem. Identify linksbetween animals, plantsand tides.
This is usually a pre-visit activity in the classroom but couldbe partially completed before a field visit to a mangrovecommunity.
What you needLarge pieces of paperPencils/crayonsCards with species drawn/pasted on, with description of
what the species eat, and where it lives (see below).
What you do
Inquiry/investigation in the classroom
Investigate photosynthesis. Construct a diagram.
What happens to the animals when the tide comes is? Whatcomes in with the tide?
Create a tide-in chart to display all those animals that comeand go with the tide.
Discuss where all the permanent inhabitants go.
Creative writing in groups or whole class
Negotiate a narrative based on the fact that the tide issomehow held back. What is the chain of events that wouldfollow? Story ends with tide being let in.
Reflection
Infer what might happen to an animal in the mangroves if thetrees were not there? In groups discuss, investigate and reporton your conclusion.
Discuss the importance of each element of the mangroveecosystem and their interrelationships.
Examine a range of food chains
Explain how the parts are linked.
Talk about how the energy flows.
Where does the energy come from?
Identify the herbivores/carnivores.
Who eats what?
Adapted from East Point
Mangrove Boardwalk, An
educational resource kit for
primary and junior secondary
teachers, Greening Australia
Northern Territory.
Examine the cards (double-sided) labelled ‘I eat ...’
Distribute one card per student. Each card has an animal/plant/organism with a briefdescription of what it eats.
Students must link themselves up to the person displaying the label of what they eat.
• What does the outcome look like?
• Is it a food chain or food web?
• Discuss and draw a diagram.
Look at the other side of the card ‘I live ...’
Discuss who lives where. Why?
Distribute one card per student, where each card has an animal/plant/organism with abrief description of where it lives.
Students must attach cards to the large wall chart of the mangroves with the tide out.
What should happen to those student with cards unable to be placed? Is one wall chartenough?
In the field
Undertake one of the mangrove field studies (‘Mangrove Community’, ‘Marine Trailing’or ‘Comparing Plant Communities’).
Extensions
Look back at the concept maps, lists and investigations and use the information to draw alarge wall chart of the mangroves with the tide-out.
Identify and describe the links between animals, plants, and other organisms that live orvisit the area.
114
The Mangrove Ecosystem
The Mangrove Ecosystem
Algae Algae
Black flying fox Black flying fox
Mudskipper Mudskipper
Mostly microscopicsingle celled plants.L a rgest are the greenseaweeds Base ofmany food chains.
Lives in hugecolonies withinmangroves
Superbly adapted toits tidal habitat
Green algae is aplant, it makes itsown food
Food: nectar fromblossoms of nativetrees and fruit
Food: small crabs,insects, amphipodsand marine worms
False water rat False water rat
Acorn barnacle Acorn barnacle
Builds nest amongroots of mangrovetrees, mound ofleaves and mud 60
Lives on tree roots,rocks and mud inthe mangroves
Food: crabs andother hard shelledaquatic life
Food: feed onplankton that driftsby with the tides
I Live I Eat
Mangrove plantslive between thehighest and lowesttidal zones
Mangrove plantsphotosynthesize, theymake their own food
The Mangrove Ecosystem
Polychaete worm Polychaete worm
Lives in a tube inthe mud made ofmucus and smallparticles of debris
Food: detritus,algae, protozoa
Mud whelk Mud whelk
Fiddler crab Fiddler crab
Bacteria Bacteria
King prawn King prawn
White-belliedsea eagle
White-belliedsea eagle
Lives on themangrove mud
Lives amongst themangrove roots
Unknown number ofspecies present inw a t e r, mud and plants
Part of life cyclespent in themangroves
Common in manyAustralian coastalhabitats
Food: extractsalgae and otherorganic matterfrom detritus
Food: plays animportant role inbreaking down plantdebris and in thedecay process ofdead animals
Food: detritusfeeder
Food: fish,carrions, smallbirds, flying foxes
Food: graze onalgae on thesurface of the mud
I Live I Eat
The Mangrove Ecosystem
Mullet Mullet
Little file snake Little file snake
Zooplankton Zooplankton
Amphipod Amphipod
Little egret Little egret
Thais Thais
Free swimmer,common inmangrove linedrivers and creeks
Common incoastal habitats
Microscopicanimals whichdrift in water
Common name‘beach hopper’, oneof the smallestcrustaceans inmarine habitats
Common inm a n yA u s t r a l i a nh a b i t a t s
Lives on treeroots, rocks, andmud in the
Food:detritus, algae
Food: small fish,other crustaceans
Food:microscopicplants, algae
Food: vital foodchain link betweenmicroscopicprotozoa and smallfish
Food: stalks fishin shallow waters
F o o d :m i c r o s c o p i cplants and algae
I Live I Eat
118
Seagrasses Are Special
Level7
Key questionsWhat is a seagrass bed?What is the importance ofseagrass?What damages seagrass?
Key outcomeUnderstand the featuresand importance ofseagrasses.
In Queensland and NSW, all seagrasses are protected and maynot be picked or destroyed. In other states, sea grasses may beprotected in marine protected areas. In areas withoutprotection, small pieces of seagrass may be picked for lateridentification. Check with local Departments of Conservationor Fisheries authorities.
What you needSnorkel equipment Underwater slates (perspex or plastic) or water proof paper
and pencilIdentification reference book on sea grassesTape measureCopy of seagrass food chain and introductory comments.
What you do
Read about seagrasses and then do the fieldwork.
Seagrasses
Seagrasses are found in estuaries and shallow coastal waterswith sandy or muddy bottoms all around Australia. The plantsusually live together in beds or meadows. There are 25 speciesin Australia, with the world’s largest single seagrass bed inShark Bay, WA. This is over 1 000 square kilometres in areaand has developed over 5 000 years. There are extensive seagrass beds in water over 50 m deep off eastern Cape York inQueensland too, and these are very important feeding groundsfor dugong.
Seagrasses require sunlight to provide energy for growth. Theleaf blades are specially adapted to capture light. Most seagrasses grow to a length of between two and twelve metres.They provide oxygen into the water, shelter for many marineorganisms, and food for fish, turtles, swans, and dugong.Small fish and prawns shelter within the seagrass beds andprovide breeding areas for many fish including commercialimportant species such as whiting, mullet, tailor, flathead andprawns. Seagrass also stabilise the sea bed, preventingerosion, and create permanent underwater communities foralgae and marine animals.
Many seagrass beds around Australian coasts are being
Adapted from 1995,
‘Seagrass’ Seanotes,
published by Ocean Rescue
2000, Department of
Environment, Sport and
Territories, and Sea Country
May 1996: Information on
indigenous issues of the Cape
York Marine Parks
(Queensland Marine Parks),
and undergraduate work in
Environmental Education and
Communication, Griffith
University, Queensland.
Hazard warning!Snorkelling requirespractice, and groups musthave shore/boat basedobservers who areproficient lifesavers.Follow safety instructionsset by education andlifesaving authorities.
destroyed by dredging of shipping canals, ports and canal estates. Extra nutrients fromsewage or fertilisers in water run off can kill seagrass. Increased sediment from storm runoff (often mixed with herbicides) can kill hectares of seagrass after heavy storms orcyclones as sunlight is blocked from the beds. Heavy metal pollution, sand-mining spoiland oil spills also damage seagrass beds. Boats, anchors and speed boat propellers cancause permanent, long term damage.
Measures to save seagrass are not succeeding. Replanting has been trialled but is provingvery slow. Aerial mapping now shows the extent of seagrass beds, and coastal managersare now aware of their importance for fish, dugong and turtles. Keeping boats away fromshallow beds, reducing sediment outflow from land, and reducing dredging are the chiefmeasures being used.
Field work
1. Decide the boundaries of the area to be covered by the whole student group andidentify markers or features to set these boundaries (e.g. buoys, edge of pier,anchored boat etc).
2. Work in buddy pairs, one of you with an underwater slate and pencil. You should beable to stand up in the water (being careful not to trample the seagrass). If the wateris deeper, make your observations quickly and return to shallower water to discussthese with your partner.
3. Roughly measure out a plot of 5 m by 5 m. Measure the depth of the water (seagrassusually grows between 2-12 m).
4. Record the approximate cover of seagrass, bare sand or rock, algae or otherseaweed, coral etc.
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Figure 1.
Two commonseagrasses
5. Carefully examine the seagrass. Identify the species (two are shown in Figure 1).Draw a sketch of one of the leaves, being careful not to pull up the whole plant.
• Can you see any roots?
• Are these growing horizontally along the sand?
• Are any plants flowering (seagrasses acts like a flowering land plant with pollenfloating in the water until they collide with a flower)?
6. Observe life under and around the seagrass.
• Does algae grow on the seagrass fronds?
• Can you see molluscs, bivalves, fish, prawns, sea hares or other marine life?
• Where are they?
• What are they doing?
7. In sub-tropical and tropical areas of Australia, you may be lucky enough to seedugong, the large ‘sea cows’ which are herbivore mammals, or green turtles grazingon seagrass. Swans, many invertebrates and some fish may be feeding directly onseagrass.
8. Lie still in the water and assess its clarity. Is there much sediment stirred up or is thewater clear (if you have a sechi disk, you can measure how far you can see underwater)?
9. Look around you across the seagrass bed.
• Do you see signs of disruption to the growth?
• Have anchors dragged across the bed?
• Is erosion of the seabed obvious?
10. When all pairs have returned to shore, compare your results.
11. Were any parts of the seabed badly eroded and without good seagrass cover?
• Where was most marine life?
• What was the average depth and clarity?
• What was the most dominant species of seagrass?
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In the classroom
1. Check your observations with Figure 2 (food chain). What elements are missing inyour observation area? Can you redraw the diagram providing local information?
2. Can you suggest ways of preserving the seagrass in this area?
3. Undertake some research into case studies of destruction of seagrass and methodsbeing used to rehabilitate seagrass.
4. Undertake research into Aboriginal and Torres Strait Islander literature about theirsea country and traditional hunting of dugong for tucker and traditional ceremonies.
ReferencesAshton, H.I. 1977, Aquatic Plants of Australia, MUP, Melbourne.Lanyon, J. 1986, Guide to the Identification of seagrasses in the Great Barrier Reef Region, SpecialPublication Series (3), GBRMPA, Townsville.1995, ‘Seagrass’, Seanotes, D.E.S.T., Canberra.
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Dugong
Turtle
Sea Cucumber
Young Fish
Prawns
Zooplankton
Phytoplankton
Seagrass leaf dies
Seagrass leaf decomposes
Nutrients used byplankton (=seagrass soup)
Decayed seagrass
Crab
Seagrass
Seabed
Figure 2. Seagrass food chain
(adapted from Seacountry May 1996)
