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A Study of The Mangrove Ecosystem
Stage 6 Biology
Fieldwork Journal
Name:
Class:
Group Name/Number:
Fieldwork Journal
page 1
Introduction
Bobbin Head is located in the Ku-ring-gai Chase National at the junction of the Cockle and Cowan Creeks.
The park is mostly used by local residents for recreational activities including picnicking, fishing, bushwalking
and bike riding.
Facilities at Bobbin Head include a marina, picnic areas and a lunch-time restaurant in what used to be the
Bobbin Head Inn, which also contains a National Parks information centre.
The area also contains many bushwalking tracks and has sites of Aboriginal cultural significance including axe
grinding grooves, engravings and midden caves.
The Study Sites
At the southern end of Bobbin Head is the Mangrove Boardwalk, a purpose built walkway that cuts through the
mangrove ecosystem as part of the longer Gibberagong walking track.
Bobbin Head Picnic Grounds
Gibberagong EEC
Marina
Empire Marina
Study site 1
Study site 2
What are some of the potential human impacts on the mangroves as indicated on this map
Fieldwork Journal
page 2
Other plant species of the Mangrove Ecosystem
Common Name River Mangrove
Scientific Name Aegiceras corniculatum
A shrub - usually up to 2m in height.
Generally found on the landward fringes of
mangrove forests.
The glossy green leaves are alternate.
Common Name Swamp Oak
Scientific Name Casuarina glauca
A tree - usually up to 20m in height
Generally found in dense strands in belts just inland
from mangroves
Branchlets: 30-50cm long, 1-2mm diameter
Common Name Saltwater Couch
Scientific Name Sporobolus virginicus
A grass that grows occurs in clumps.
Generally found in salt marshes and on sand-dunes
Leaves are short, with stems about 1mm wide
Source: www.dse.vic.gov.au/
Common Name Sea Rush
Scientific Name Juncus kraussii
Large, rigid, clumping forming perennial to 120 cm
tall with an extensive rhizome system. Leaves and
flower stems are tough, have pithy centres and taper
to sharp points. Flower-heads are generally many
branched with clusters of flowers towards their ends.
Source: www.dse.vic.gov.au/
Common Name Sea Blite
Scientific Name Suaeda australis
Herb low dense spreading, sometimes a Shrub 10-30 cm, Shrub to 60 cm.
Tidal Wetlands, salt flats, Drier, well drained, midlower tidal zone.
Source: www.noosanativeplants.com.au/
Common Name Creeping Brookweed
Scientific Name Samolus repens
Samolus repens has small white or occasionally pink
flowers with a flowering period from September
through to March or April
Source: http://www.chah.gov.au/
Fieldwork Journal
page 3
Other animal species of the Mangrove Ecosystem
Common Name Sand Whiting
Scientific Name Sillago ciliata
Sand Whiting are silvery white in colour with plain
yellowish sides.
Sand whiting feed on marine invertebrates including
crustaceans (yabbies, prawns and soldier crabs)
Source: www.shorefishingaustralia.com.au/
Common Name White-faced Heron
Scientific Name Egretta novaehollandiae
Mostly blue-grey in colour with a white face, Whitefaced Herons have a long thin neck, pointed greyblack bill and long legs.
They feed on a variety of prey including insects,
amphibians and fish
Source: http://birdsinbackyards.net/
Common Name Sydney Rock Oyster
Scientific Name Saccostrea glomerata
They have a thick shell with a smooth exterier
surface and are usually found in the intertidal zone
to 3 metres below the low water mark.
They are filter feeders, straining planktonic algae
from the water. They are prey to a variety of fish.
Common Name Tarwhine
Scientific Name Rhabdosargus sarba
The Tarwhine can be recognised by its silver body
with rows of yellow spots forming stripes.
It grows to 45 cm and weights up to 1.4 kg.
Their main diet consists of prawns, worms and small
crustaceans.
Common Name Shrimp
Scientific Name
Shrimp are small animals that live on the floor of
oceans and lakes. Shrimp are invertebrates (animals
lacking a backbone) that have a tough exoskeleton.
Shrimp are omnivores; they eat plants and small
animals
Source: www.sea-ex.com/fishphotos/oyster,.htm
Fieldwork Journal
page 4
Identifying Two Species of Mangroves
Write down at least 7 observable differences between the two mangrove species. Be sure to look at height,
leaves, flowers, fruit.
Plant Adaptations
Plant
Common Name Grey Mangrove
Scientific Name Avicennia marina
Diagram
Adaptations
Draw a labelled diagram (include height, a leaf and
fruit)
Describe three adaptations
1.
2.
3.
Word bank: pneumatophores, viviparous, excretion, exclusion
Fieldwork Journal
page 5
Identifying Two Species of Crabs
Crab 1
Common
Name
Diagram
Draw a labelled diagram of one of the crabs
Animal Adaptations
Adaptations
Describe three adaptations of the crab
1.
2.
3.
Word bank:
Crab 2
Common
Name
Fieldwork Journal
page 6
Measuring Distribution and Abundance of Adult Crabs Across the Intertidal Zone
and Relating This to the Abiotic Factors
Observation: At what site (1,2,3 or 4) do you believe most of the adult crabs are located?
________________________________________________________________________________
Hypothesis: Make a statement concerning what abiotic factors may affect the distribution of adult crabs.
________________________________________________________________________________
Task: To measure the distribution and abundance of adult crabs across the intertidal zone and relate these to
the abiotic factors of the environment.
Procedure:
1. Identify the four study sites as pictured below.
2. Randomly place a one metre quadrat in the first study site. Count the number of adult crab holes in the
quadrat (an adult crab hole is larger than 1cm diameter)
3. Record your data in the table on the following page.
4. Use the procedures as outlined to measure the abiotic factors at this site.
5. Record your data in the table.
Diagram 1: Profile of a Typical
Mangrove Ecosystem
showing study sites
2
4
1
3
Results:
Complete your results on the next page
Data Analysis and Discussion:
Fieldwork Journal
page 7
Results
a. Abundance of crabs across the intertidal zone
Group
Site 1
Site 2
Site 3
Site 4
Site 1
Site 2
Site 3
Site 4
Totals
Average (Total/no. groups)
b. Abiotic Factors Across the Intertidal Zone
Parameter
Soil Moisture 0-10 (10 is very wet, 0 is
very dry)
Instrument: none
Air Temperature (0C)
Instrument: thermometer or Kestrel
Humidity 1m above ground (%)
Instrument: hygrometer or Kestrel
Wind Speed
Instrument: anemometer or Kestrel
Light Intensity 1m above ground
Instrument: light meter
Soil Temperature 10cm below
Instrument: soil thermometer
Interpretation
Fieldwork Journal
page 8
Relating Abiotic Factors to the Distribution of Plants Across the Intertidal Zone
Hypothesis: Make a statement concerning the distribution of one of the plants
____________________________________________________________________________________________________________________________
Task: To measure the abundance and distribution of plants across the intertidal zone and and relate this to the abiotic factors measured
Procedure:
1. Lay out a straight transect line of 30m through the vegetation from either the landward or shoreward edge of the intertidal zone
2. Using a builders string and spirit level, prepare a level string above the tape measure
3. Undertake a belt transect, placing the 1m2 quadrat at one metre intervals along the transect
4. Count the total number of each plant listed below within each of the quadrats and complete the table on the next page (abundance and distribution)
5. Within the centre of each quadrat, measure and record each of the abiotic factors and complete the table on the following page (abiotic factors)
6. Complete your data analysis and discussion below.
Results:
Complete your results on the next page
Data Analysis and Discussion: Discuss your results with regards to your hypothesis
Fieldwork Journal
page 9
Results
a. Plant Abundance and Distribution Across the Intertidal Zone
Plant species
0-1m
2-3m
4-5m
6-7m
8-9m
1011m
1213m
1415m
1617m
1819m
2021m
2223m
2425m
2627m
2829m
3031m
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
Q10
Q11
Q12
Q13
Q14
Q15
Q16
Grey Mangrove
River Mangrove
Casuarina
Juncus
Sea Blite
Saltwater Couch
b. Abiotic Factors Across the Intertidal Zone
Parameter
Elevation (cm)
Air Temperature 1m
above ground (oC)
Soil Temperature 10cm
below ground (oC)
Humidity 1m above
ground
Soil Moisture (10 is
very wet, 0 is very dry)
0-1m
2-3m
4-5m
6-7m
8-9m
1011m
1213m
1415m
1617m
1819m
2021m
2223m
2425m
2627m
2829m
3031m
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
Q10
Q11
Q12
Q13
Q14
Q15
Q16
Total
No.
Average
No.
Total/
No. Quad
Fieldwork Journal
page 10
Results
c. Cross-section results (Optional)
Plant Key
Key
Topography (cm)
Swamp Oak
Grey Mangrove
River Mangrove
Saltwater Couch
Sea Rush
wwww
Sea Blite
Creeping
Brookweed
ooooo
Unknown
iiiiiiiiiiiiiiiiiiii
xxxx
Height
below
cm
0
String
line
20
40
60
80
100
0-1m
2-3m
4-5m
6-7m
8-9m
10- 11m
12- 13m
14- 15m
16- 17m
18- 19m
20- 21m
22- 23m
24- 25m
26- 27m
28- 29m
30- 31m
Fieldwork Journal
page 11
Interactions Between Organisms in Mangrove Environments
1. Beneficial and Detrimental Relationships
Name interacting organisms and briefly describe the nature of the interactions
Gain
Mutualism
Mutualism 1:
Algae
Loss
Gain
Loss
Gain
Loss
Parasite:
produces food
Mutualism 2:
Commensalism
Parasitism
Host:
Gain
Loss
Allelopathy
Commensal:
Allelopath:
Host:
Competitor:
Fieldwork Journal
page 12
2. Trophic Interactions
Use the diagram opposite and observations from today to complete the
following observation table and food chains to show energy flow using
organisms in this ecosystem. Include the trophic level.
The trophic levels are producer, primary consumer (herbivore),
secondary consumer (carnivore), tertiary consumer (large carnivore) or
decomposer.
Name
Food
Food Chain
Food Chain
Sun
Sun
Trophic Level
Mangrove
Producer
______________
______________
______________
______________
______________
______________
Fieldwork Journal
page 13
http://www.daff.qld.gov.au/fisheries/habitats/marine-plants-including-mangroves/dead-marine-wood
http://www.environment.nsw.gov.au/resources/waterwatch/estuaryGuideStudents/20100686EstuaryFactWorksheets.pdf