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A investigation took place at a large mangrove community called the ‘Badu Mangroves’. The interactions of organisms and the Badu Mangrove ecosystem were observed. While experiments were carried out to determine the abiotic ( e.g. temperature, humidity, soil pH ) and biotic ( e.g. number of seedlings distributed throughout a certain area, adaptations of animals ) features in the Badu Mangrove community.
The aim of this report was to explore the abiotic and biotic features concerning the growth and placement of grey mangroves (Avicennia Marina ) in the Badu Mangrove community at Sydney Olympic Park. The surface area of the Badu Mangroves is approximately 38 hectares, its location is Latitude: 33˚51’48.7″S Longitude: 151˚04’32.07″E Factors that influence the mangroves’ lifestyle were also investigated.
The air and water temperature of the Mangrove site was measured by using a thermometer. A thermometer was obtained and it was held in the air for a few minutes until the reading became stable. The temperature was then recorded.
When measuring humidity, a psychrometer was used, along with a information chart. The psychrometer contained a wet bulb which measured the wet temperature while the normal thermometer on the psychrometer measured the air temperature. The dry temperature was subtracted from the wet temperature. The result of this subtraction was then interpreted by using a table and this determined the humidity.
The light was measured in a spot where there were vegetation which had leaves and long trunks. This was done to observe how much light could penetrate through the vegetation. A light meter was obtained and it was turned face down in a spot were there was moderate light to ensure a fair result. The light meter then showed the light intensity in units of flux. The results were recorded.
Wind velocity was recorded by using a wind meter. The meter was placed high up in the air to prevent and sources that could generate or block wind movement. The reading produced on the meter was recorded.
A sample of water was taken from a creek. A thermometer was then obtained and placed immediately into the water to prevent any heat loss or transfer of heat from the water. The thermometer was left there until a reading was steady and the temperature was recorded.
Turbidity was measured by using a turbidity tube. This tube measures the cloudiness of the water. The sample of creek water was obtained and it was placed into the tube until the lines at the bottom of the tube was no longer visible. The reading of the water level was then recorded, it was interpreted by using a table which determines the turbidity of the water, the units were recorded in NTU ( Nephelometric Turbidity Unit )
The amount of dissolved oxygen in the water was measured by using an Aqua dissolved energy meter. The wire which connected the measuring tube was placed into the water until there was an even reading, the results were recorded. The units of dissolved oxygen were measured in ppM ( parts per million ) .
The salinity of the water was measured by using a WP-83 conductivity salinity meter. The wire which connected the measuring tube was placed into the water until there was an even reading, the results were recorded. The units of the salinity was measured in ppK ( parts per thousand).
The pH of the soil was measured through the use of a universal indicator. A small sample of soil was taken and it was placed in a small petri dish, barium sulfate was then added to the soil and then the universal indicator was then added. The colour observed was then interpreted by using a colour pH chart, where the colour observed is matched with the colours on the pH. The pH was then recorded.
A soil thermometer was obtained to measure the soil temperature. The apparatus had a metal needle which was placed 5cms into the ground. The apparatus was allowed to stay there for a few minutes until a stable reading was seen on the thermometer. The temperature was then recorded.
Soil moisture was measured by using a moisture meter. The meter had a metal needle which was placed 5cms into the ground. The meter was allowed to stay there for a few minutes until a stable reading was seen on the meter. The scaled used were on a scale of 1-10. 1 being the driest and 10 being the wettest.
At the boardwalk. Ten quadrats were randomly placed along the side of the boardwalk. The number of mangroves seedlings and crabholes were counted and recorded.
Along the boardwalk, some mangroves and pneumatophores were observed.
The underneath of a mangrove leaf was licked. The taste was recorded.
Then a pneumatophore was obtained, it as plugged into a pipette. The pipette was then placed into a plastic cup filled with water. The air in the pipette was squeezed and the observations were recorded.
A ruler was used to measure the height of pneumatophores at intervals of one metre, when the distance reached ten metres measuring was stopped. The pneumatophores were measured first from the creek and it was then measure on outwards till the distance reached ten metres. This was done to prove if pneumatophores are longer near creeks and they start to get short as they grow further from the creek.
At the FSC Bund there were ten metre intervals which were marked out by poles. At each of these intervals, the height of the mangroves were estimated and sketched out as a transect. This was done until eighty-metres of mangrove forests were covered. Observations of flora and fauna were also noted down.
Abiotic factors (Air, water and soil factors)
Factor Mangrove Forest
(10:00am) Dry Forest
Air temperature 26.5˚C 34˚C
Humidity 64.5% 42%
Light Intensity 3300 lux 2710 lux
Wind Velocity 0.0m/s 0.5m/s
Water Temperature 23.4˚C n/a
Turbidity 40 NTU n/a
Dissolved oxygen 33.8 ppm n/a
pH (Water) 7 n/a
Salinity 23.7 ppk n/a
pH (Soil) 6 5.5
Soil Temperature 20˚C 22˚C
Soil Moisture Wet – 10 Dry – 1
Biotic Factors (Abundance)
Quadrats of Mangrove Seedlings and Crab Holes (11:00am)
Quadrat 1 2 3 4 5 6 7 8 9 10
Distance from Creek (m) 25 40 35 30 25 20 15 10 5 0
Number of seedlings 52 72 38 58 29 36 19 38 1 0
Number of crab holes 0 0 0 0 4 7 13 13 3 25
Biotic Factors (Adaptation)
Mangrove Leaf: When the mangrove was licked, it tasted salty.
Pneumatophores: When the pipette was squeezed little, tiny air bubbles started to come out from the little lenticals on the surface of the pneumatophore..
Do pneumatophores grow longer as they reach the creek?
Distance from Creek (m) 0 1 2 3 4 5 6 7 8 9 10
Pneumatophore 1 (cm) 31 24 21 21 13 10 13 7 10 7 5
Pneumatophore 2 (cm) 28 16 12 19 10 8 11 7 7 5 7
The places which contained more light had more flora growing there, because the light allows photosynthesis, while the spots where light couldn’t penetrate to the forest floor due to the overhead leaves blocking the sunlight out there were little vegetation growing. This shows that vegetation grow more efficiently in spots that allow photosynthesis to occur.
Spots that were more humid made no difference to the placement of mangroves. The spots that have more leaves and less sunlight seems to effect the humidity levels. The mangroves and its leaves acts as a cover to stop all the water vapour from evaporating, while in spots that had less leaves and cover they were less humid.
Wind speed could be affected the mangroves act as a barrier and they block all the wind from travelling efficiently throughout the forest, while in places were there were less trees there was a big difference in wind speed.
Soil Temperature and Soil Moisture is affected by how close the site is to a water source. In the mangrove forest, the soil temperature is lower because the sunlight is blocked from heating up the soil, and the forest is very close to a creek which could cool down the soil. While in the Dry Forest the soil temperature is higher because it has a direct contact with the sunlight and is no where near a water source. This call also affect the distribution of flora because some vegetations need to have water to grow.
This could be affected by the temperature the day before, so this could alter the results into the wrong direction. To improve this we have to find a day which as a moderate temperature so we can try our best to find the closest possible results.
pH of the Soil and Water can effect how the distribution of vegetation occurs. Some plants need a specific pH to live and thrive, if it is to acidic or alkalic the plant will die off. So the pH of Soil and Water is a very important thing concerning the growth of vegetation.
Some errors of this experiment is that the soil seemed to be alkalic but with the past tests the soil was neutral so this must have been an error. To improve this it is a good idea to use a good quality indicator that allows us to have an accurate result everytime.
The results of the Mangrove Seedlings shows that in quadrat ten there is no mangrove seedlings while in quadrat two there are seventy-two mangrove seedlings. The tenth quadrat is the closest to the river while the second quadrat is 72 metres away from the quadrat. This relation shows the mangrove seedlings only thrive when they are far away fro the river. This means that mangrove seedlings grow away from the river because the tide is too strong and they don’t have time to root themselves down and be stable. The nutrients found on the soil could be washed away by the current and leaving the seedlings close to the creek without a source of food and they will soon die off, while when they grow farther away from the creek there is no current to wash away the nutrients.
In quadrats one to four there are zero Crab Holes while in quadrat ten there are twenty-five crab holes, and once again quadrat ten is the closest to the river. This suggests that the crabs like to be closer to the creek because their food source is there, they eat decaying matter called detritus which is decaying mangrove leaves, they are deposited on the mud flats as the tide pushes it out. Also a possibility is that the crab like the water and it helps them cool down.
Quadrat nine is underwater so we are forced to make an estimate the could alter the results.
The transect drawn shows that the mangrove grew higher and bigger when the were close to a source of water. Then they started to grow shorter. This information shows that mangroves will live better and grow bigger and taller near the water. This could be used to explain that mangroves need water to thrive, and as the mangroves distant themselves from a water source they will not be able to grow.
The water source observed seemed to be the end of the a river, so when the tide comes in they bring in lots of nutrients and many seedlings that have been washed away before. At this point the mangroves closest to the water can use this to their advantage because the can take up all the nutrients and not share it with the other trees, and the nutrients cannot be transported to the other trees because there is no water current. Also the washed away seedlings have a second chance to root themselves down and grow.
The Mangrove Leaf which had a salty taste under its leaf is an adaption used by the mangroves. The mangroves live in a salty environment so they have to find ways to exert this unneeded salt. The salt can be removed from the mangrove by the tree sweating out the unneeded salt through under it leaves.
Pneumatophores are little sticks that stick out of the ground, these are the roots of the tree. The pneumatophores sucks in oxygen through its tiny lenticals and transfers it throughout the plant. This was proven through the pipette experiment, as tiny air bubbles show that air can be transferred. This is useful because when there is a flood and oxygen is not allowed to the roots of the mangrove the pneumatophores can come in handy as they stick out of the water and take in all the oxygen. Pneumatophores can also act as a filter, they can filter out unneeded salts.
Do pneumatophores grow longer as they reach the creek? As the pneumatophores travel further away from the creek there size decreases in height. This happens because the pneumatophores has to be higher than the depth of the water because it needs to suck in the oxygen available and if its under the water it is useless. As the height of the water decreases as it moves out from the creek the height of the pneumatophores also decreases.
There are some examples of commensalism in the Badu Mangrove community. A dew drop spider and a golden orbweavers are an example of commensalism. A dew drop spider lives in the golden orbweavers nest without the orbweaver realising it, because the dew drop spider is very tiny and looks like a normal dew drop hence the name. The dewdrop is the commensal because it uses the host’s ( golden orbweaver) nest and eats the food collected by the orbweaver and doesn’t harm the orbweaver in any way.
An example of mutualism in the Badu Mangrove community is lichen which consists of algae and fungi. The algae produces photosynthesis while the fungi provides a place to live.
An example of allelopathy is the casuarina (she-oak). It produces chemicals in the soil which are poisonous to other plants and this prevents anything from growing near it, also it has stem and leaves which give off these aromas that detract plants from growing near it. This allows the casuarina to nutrients to itself.
It can be concluded that the biotic and abiotic features of an ecosystem can effect distribution and population of organisms such as mangroves because they determine where they live and where they cannot live. The biotic and abiotic features of an ecosystem is very important to the many species that depend on it, if it is removed it can cause a chain of detrimental effects.