Towra Point Essay

Towra Point Nature Reserve is a place of many different land habitats. It is located in Southern Sydney, New South Wales, in eastern Australia. It produces the largest estuarine wetland complex in NSW and is a protected nature reserve. It Represents around half of the remaining mangrove area near Sydney, and most of the salt marshes area remaining in the region as well. They are also most likely one of the most major contributors to the food web within Botany Bay and provide habitat for many important fish and different invertebrate species of the bay.
(SSEC, 2013)

This Report will inform the features of the Towra Points ecosystem, its animals and plants’ adaptations, Results that were collected from an excursion to the location, abundance for mangroves and animals, and also the effects of humans on this nature reserve.

Study Area - Towra Point

Towra Point is a very important and significant wetland in the Sydney, New South Wales region, it is also important at a international and national level. Towra Point Nature Reserve is approximately 16 kilometres south of Sydney, and is at the mouth of the Georges River which is in Botany Bay. Towra Point includes important terrestrial vegetation and wildlife habitats, and is

surrounded by mangroves, sea grass beds and bird habitats. Towra Point Nature Reserve and the adjacent Towra Point Aquatic Reserve form the most diverse and largest estuarine wetland complex in the Sydney region. The entrance to the Towra Point Nature Reserve is from the Captain Cook Drive, turning into a short roadway and parking there.
(SSEC 2013, Australian Wildlife 2014)

Towra Point Nature Reserve is one of the largest wetland of its type in the greater Sydney region. Towra Point Nature Reserve is located at approximately 34-S, 151-10E and is 4km from Kurnell Point on the Southern side of Botany Bay in Sydney, Australia. It is about 16 kilometres from the Sydney City. Botany bay is located on the central coast of New South Wales, Australia. Botany Bay is an oval-shaped bay which is open to the Pacific Ocean through the La-Perouse and Kurnell areas. The Georges River drains into it from the South-west of the bay. This river leads into Towra Point.
(SSEC 2013, Australian Wildlife 2014)

Study Results
Animal Adaptations

An Adaptation is a genetic change or a mutation that helps an organism . such as an animal and plant to survive in its environment. Due to the very helpful nature of the mutation, the mutation is passed down from one generation to the next one. As more organisms inherit the mutation, the mutation becomes an adaptation.
(NGE 2015, Biology Online 2014)

Figure 1 - Soldier Crab (AusPhotography, 2015)

The Soldier Crab lives in sandy areas and mangroves. The Soldier Crab as seen in figure 1 is very distinctive with its small, blue, round body on long legs with purple stripes. As the soldier crab marches around feeding, it builds the sand into numerous pallets, going through it for organic matter. There is only one other species of soldier crab common in Sydney which is the smaller Mictyris Platycheles.
(Australian Museum 2014, AUSECO 2015)

Apart from obvious and clear external structural differences in the crab there are many internal differences that make them very successful in their particular habitat. Within the crabs thorax is a chamber containing the gills and the lungs. These gills take up the lower part of the thoracic cavity. The upper part of the cavity has a complex set of tiny tubes, which are highly made, to allow efficient exchange of the different gases, carbon dioxide and oxygen. These soldier crabs obtain approximately 90% of their oxygen from their lungs. Their access to air is facilitated by a hole in their forward part of the carapace (shell). This allows the Soldier Crab to breathe both in and out of water.
(Australian Museum 2014, AUSECO 2015)

Plant Adaptations

Plants have adaptations to help them survive in many different areas. Plant adaptations are special features which allows a plant or animal to live and survive in a particular place or habitat. These places’ adaptations might make it very difficult for the plant to survive in a different place. This shows and explains why certain plants or plant species are found in one area, but not in another area. For example, you wouldn't see a cactus plant living and surviving in the Arctic, and Nor would you see lots of really tall trees living and surviving in grasslands.

(MBG 2009, DAF 2014)

Mangroves are trees that originally are evolved from trees growing in rainforests located near the sea. They occur in swamps or wetlands that are regularly inundated by the sea during tidal fluctuations. The boundary between mangroves and adjacent vegetation is defined by the high tide limit. There are over thirty mangrove tree species occurring on the east coast of Australia but only two in the Sydney Region.
(AUSECO 2014, DAF 2010)

Figure 2 - Grey Mangrove (DAF, 2010)

Avicennia marina (grey mangrove) refer to figure 2 for image, belongs to the family called Avicenniaceae. It is approximately the most common and widespread mangrove found along the mainland coast of Australia. It is the only mangrove species able to withstand the cooler climates of South Australia and Victoria.Grey mangrove occurs in intertidal zones on a range of soft muds to sandy soils. It is common along the tidal margins of estuaries and along saline or brackish river areas where it may grow with river, red and other mangrove species. As a pioneer species, grey mangrove commonly colonises developing mud banks.
(AUSECO 2014, DAF 2010)

Abiotic Factors

Abiotic factors are non-living conditions which can influence where plants or animals live. Some examples of abiotic factors include Examples of abiotic factors include: temperature, light intensity, moisture content of soil and pH of the environment.
(BBC 2014, AUSECO 2014)

Aquatic and terrestrial environments are different in their physical and chemical characteristics. these include the factors such as the temperature shown in table 1, which was the temperature of the water and the air, salt concentration shown in table 3, which was a sample of estuary water in a bottle and used a refractometer to measure the salinity, light Intensity shown in table 2, which was the measurement of light intensity in the mangroves area and sand dunes area. pH shown in table 4, which was a sample of seas water and turbidity shown in table 5. As a result of these many different conditions, the organisms that live in water or live on land show various different adaptations to enable them to function in their given environment or habitat.
(AUSECO 2014, BBC 2014)

Table 1 - At Temperature from various locations at Bonna Point Reserve
Location
Temperature (°C)
Water
19(°C)
Mangroves (Air)
21(°C)
Sand Dunes (Air)
22(°C)

Table 2 -Light intensity (lux) - Light reading at various location in Bonna Point Reserve
Location
1
2
3
4
5
Mean
Mangroves
70
80
85
79
65
753.8
Sand Dunes
285
305
306
310
313
303.8

Table 3 - Salt Concentrations
Location
Salinity (grams/Litres)
Estuary
28
Fresh Water
0
Ocean Water
35

Table 4 - pH
Location
pH
Estuary
7.5
Sea
7.7

Table 5 - Turbidity
Turbidity (m)
1.3

In graph 1, It shows the change of weather through the course of the month. This information has been retrieved from the (BOM, 2015) as we were unable to collect this information at the time of the excursion.

Mangrove Population Abundance

To measure the Abundance of Mangrove Population in the full area of Towra Point. The Quadrats were laid out in random positions which were generated by a online software around a large map of Towra Point, we tested this 17 times shown in table 6. These quadrats were 5 by 5 millimetres squares which made 25 squares.

Table 6 shows the percentage cover at the random position we placed the quadrat. Towra Point nature reserve is approximately 603.7ha and the percentage cover is 70.4% approximately. Which gives the answer 425.0048ha (4.250048 km2) of land is approximately covered by mangroves.

Table 6 - Percentage cover of the population of mangroves at towra point
Percentage cover of mangrove

21/25 - 84%
14/25 - 56%
23/25 - 92%
17/25 - 68%
19/25 - 76%
5/25 - 20%
9/25 - 36%
17/25 - 68%
23/25 - 92%
15/25 - 60%
16/25 - 64%
17/25 - 68%
25/25 - 100%
25/25 - 100%
21/25 - 84%
22/25 - 88%
10/25 - 40%

Mangrove Population Distribution

Mangrove plants or forests thrive near the mouths of large rivers where different rivers provide lots of sediment.

Mangrove roots collect sediments and slow down the water's flow, helping to protect the coastline and preventing erosion overtime. Over a long period of time, the roots can collect enough debris and mud to extend the edge of the coastline further out. Mangroves are teeming with life. Shorebirds, Soldier Crabs, Crab-Eating Monkeys, and fishing cats all make the mangrove home or habitat. Mangroves provide a safe place to live or home and a nursery for a variety of fish, birds, crustaceans, and

shellfish.
(MBG 2002, AUSECO 2014)

There are 15.9 million Ha (which is over 60,000 square miles) of mangrove forests waters of tropical oceans all over the world. All along the Atlantic coast they are found from Florida all the way down to Argentina. The Mangroves grow on both the western and eastern coasts of the continent Africa. They stretch into Burma, South-East Asia and India. Mangrove forests are also common in New Zealand and Australia.
(MBG 2002, AUSECO 2014)

Animal Population Abundance

Table 7 - Number of Soldier Crabs captured, marked and recaptured.

To catch the Soldier Crabs we used Pitfall trapping which is a sampling technique which is used a lot for studies of seasonal occurrence, to examine spatial distribution patterns, to compare relative abundance in different habitats and to study daily activity and rhythms happening. We did a simulated capture recapture technique where we assumed that at these four positions shown in figure 3, there were pitfall trappings placed and the results were recorded as shown in table 7.
(Animal Ethics 2014)

Using recapture system the calculations that have been worked out for the Population of each site Shown in table 8, you can see the results that have been gathered in table 8 and with these results it is possible to work out the population abundance using the formula Population Abundance = (Total number captured * Total number recaptured) / (No. marked in recaptured) Which translates to 190x229/120 = 363 (rounded up because there is not half a crab). This means that there are approximately 363 Population Abundance of Soldier Crabs in the area shown in Figure 3.

Table 8 - Results of Captured and recaptured soldier crabs
Sites
Initially Captured
Total Recaptured
Total Marked
Site 1
43
38
15
Site 2
27
36
12
Site 3
54
49
38
Site 4
66
106
55

Total = 190
Total = 229
Total = 120

Figure 3 - Area of the colour of marked Soldier Crabs (Google Maps, 2015)

Animal Population Distribution

At Towra point Soldier Crabs are found are found in sandy estuaries and mangroves, and occur in massive groups that seem to emerge from nowhere all at the same time. They are found near the mangroves shore and some are in under the water as well as the tide gets lower and higher we tend to see them more and not that much.
(Australian Museum 2014, AUSECO, 2014)

In the larger world Soldier crabs live on tidal mudflats in sandy estuaries and mangroves. In Australia they are found from Western Australia around the top end of Australia to Wilson’s Promontory in Victoria, Also in botany bay in Sydney (Which is Towra Point). They are also found on islands of the western Pacific Ocean including New Caledonia and also South-East Asia.
(Australian Museum 2014, AUSECO, 2015)

Discussion

Trophic Interactions

Trophic Interactions are the interactions between trophic levels of different species. Trophic Interactions refer to how producers, primary consumers (herbivores), secondary consumers and tertiary consumers (carnivores) affect each other. There are limitations on how much energy can flow between these trophic levels as well as the amount of biomass in each level.
(J.West & R.Caddy 2004)

Figure 4 - A simple food web in a mangrove ecosystem (Preliminary Biology, 2004)

The Pyramid of Biomass - Biomass is an estimate of the amount of matter in a given population of organisms. The biomass of a trophic level is estimated by finding the dry weight of an organism in the trophic level then multiplying by the total number of organisms in the population. Biomass for different trophic levels is compared in a biomass pyramid to see how the quantity of matter in living things changes along the food chain.
(AUSECO 2014, J. West & R.Caddy 2004)

Figure 5 - Pyramid Of a Biomass (J. West & R.Caddy 2004)

As shown in figure 5, the base of the pyramid represents the matter in producers. The next level shows the biomass of first-order consumers and so on to the top of the pyramid and to the end of the food chain. Also notice that each level in the biomass pyramid is smaller, and has less biomass each, then the level below it. This shows that the biomass is being lost. If you think of it as a carnivore eating a herbivore, only a little part of the herbivores body becomes part of the carnivore. Some of the parts are indigestible and is passed out as faeces. Some of the energy is converted into the energy required for living.
(AUSECO 2014, J. West & R.Caddy 2004)

Pyramid Of Energy - A pyramid of energy looks very similar to the pyramid of biomass shown in figure 6, but an energy pyramid depicts the total energy in trophic levels and shows how energy is lost along a food chain.
(AUSECO 2014, J. West & R.Caddy 2004)

Figure 6 - Pyramid of Energy (J. West & R.Caddy 2004)

Almost all the energy in an ecosystem come from the sun. A producer uses only 10% of the sunlight falling on it. A herbivore that eats the producer incorporates only about 10% of that energy. In other words there is a loss of 90% of energy during the trophic interaction. This energy loss is repeated with each trophic interaction along the food chain.
(AUSECO 2014, J. West & R.Caddy 2004)

Competition for Resources

At Towra Point there are many different kinds of competition for resources these might be a competition for food, habitat, nesting sites, light, shelter, mates, water and area of land they want. Members of the same species may compete for example, there is a limited amount of food at Towra Point for a bird species to eat. If there are too many of them some will starve and die. If those numbers fall, more chicks will survive because more food will be available to them. Over the short term, The population of the species will remain fairly stable.
(J.West & R.Caddy 2004, AUSECO 2014)

Over the short term, there is often competition between members of different species. If one species at Towra Point has an clear advantage over the other species which cannot keep up in terms of living and fighting with each other for resources, it will limit the growth of that population or may even not let it stay at Towra Point at all. In the long term competition for resources, competition between different species at Towra Point it may also lead to the extinction of the disadvantaged species. For example nesting holes are important but are a limited resource for many different species of birds at Towra Point.
(J.West & R.Caddy 2004, AUSECO 2014)

Human Impacts

There are many Human Impacts that effect Towra Point in few good ways and bad ways as well. These include A large amount of sea grass is washed up on the beach which disturbs the sea grass under the bed which is done by power boating and by dredging. On the positive note this provides food for crabs and some other land animals but is not equal to the amount of damage done to the sea bed itself which destroy so many homes and more food for other sea creatures or species.
(J.West & R.Caddy 2004, AUSECO 2014, AUSECO 2015)

Another important human impact on Towra Point is the development and building of port botany. Building this port is placing more sand on the water to make land which destroys animals living in the water they are building on top of that area right now. The buildings being built and sand being placed will use machines which will also pollute the water which will go and spread very far maybe even further than the whole of Towra Point.
(J.West & R.Caddy 2004, AUSECO 2014, AUSECO 2015)

A big human impact at Towra Point also includes dredging which causes erosion and you can destroy the sea beds in the water. Which destroys the animals habitat and if that is lost and they have no where to move to then they will die. This brings the sea grass to the surface instead of the water which is also a loss of protection for some animals and will not live in a result to the loss of their protection.
(J.West & R.Caddy 2004, AUSECO 2014, AUSECO 2015)

Also a changed wave energy entering Botany Bay through dredging have created a channel to allow ships to enter, this is combined with the hard structure of Sydney Airport runway and Port Botany that have created changed water movements, sand erosion and deposition. Due to sand deposition it has covered a lot of the sea grass beds, and while erosion has attacked Towra Beach and the sand spit. The area Elephant Trunk at the western and of Towra Point has been branched in a number of places.
(J.West & R.Caddy 2004, SSEC 2013)

Conclusion

The study point of Towra Point Nature Reserve which is located in Southern Sydney, New South Wales. This report has information on the features of an ecosystem, information on adaptations and gathering of information on the excursion. The adaptations of mangroves and soldier crabs are very important for them to survive in Towra Point and abundance wise there are many of them. Their distribution over Towra Point is very spread and is good in a way for a spread habitat for other animals as well. Trophic interactions are very important in the Towra Point ecosystem and each step is vital for another animals life. At Towra Point there is a lot of competition for resources but these competition will be in almost every single ecosystem in the world. Lastly human impacts has a great effect in a negative and positive way on Towra Point, but lately the negative is taking up more impact than the positive. This can be fixed very easily as soon as possible or it will be too late and the whole ecosystem will be destroyed if not fixed soon.