Download
1 / 34
340 likes | 515 Vues
Study of Stream Ecosystem. The C.C.C. Ming Yin College 19 / 1 / 2006. Introduction. Aims To compare the biodiversities at site A and site B. To promote our environmental awareness. Locations of Site A & Site B. Profile of Site A. Profile of Site B. Site A. Site A.
E N D
Study of Stream Ecosystem The C.C.C. Ming Yin College 19 / 1 / 2006
Introduction Aims • To compare the biodiversities at site A and site B. • To promote our environmental awareness.
Site A • The area is shaded by canopy of trees. • Light intensity is low. • Fallen leaves can be found. • The sediment is mainly composed of sandstones. • The water is clear. • Slow waterflow.
Site B • Large number of stones with different sizes lie at the bottom of the stream. • Fast waterflow. • Aquatic animals are rarely seen. • Adequate sunlight. • Cool but not windy.
1. Suspended solid particles of the water sample cannot be determined in site B. Reason: Water vapour in the air was absorbed by the filter paper before weighing yesterday. 2. Chemical oxygen demand of the water sample cannot be determined in site A. Reason: Personal error. Too much permanganate solution was added after end point was reached.
Freshwater Plants All the plants found in Site A and Site B are different.
Comparison for the number of organisms and the biodiversity in site A and site B ‧Plants In general, there are fewer plant species in site A than in site B. However, the total numbers of plants in the two sites are about the same. A total of 9 plants can be found in site A and a total of 10 plants can be found in site B. There is no common plant in the two sites. A total of 2 plant species can be found in site A, namely, taro and sweet flag. Taro is the dominant species in site A, 7 of which can be found. Only 2 sweet flags can be found. A total of 5 plant species can be found in site B, namely, day-flower, water celery, water cress, greaterduckweed and moss. Greaterduckweed is the dominant species in site B, 5 of which can be found. While for the other species, only 1 or 2 of which can be found.
Site A has a large tree, so there is a large canopy and less sunlight can reach the freshwater. Plants can’t get enough light for photosynthesis so that there are little freshwater plants. There are only Taro and Sweet Flag. Site B is exposed to sunlight directly so there are many different species of short freshwater plants in site B such as Day-flower, Water Celery, Water Cress, Greaterduckweed and Moss.
‧Animals In general, there are fewer animal species in site A than in site B. However, there are slightly more animals in site A than in site B.A total of 37 animals can be found in site A and a total of 33 animals can be found in site B. Mayfly nymph, small stream leech, Hong Kong newt and reservoir snail are found in both sites. A total of 6 animal species can be found in site A, namely, mayfly nymph, large stream snail, small stream leech, Hong Kong newt, reservoir snail and goby. Large stream snail is the dominant species in site A, 22 of which can be found. Reservoir snails are the second most abundant organisms in site A, 8 of which can be found. For the other species, only 1-3 of which one can be found. A total of 8 animal species can be found in site B, namely, mayfly nymph, viviparous snail, dragonfly nymph, small stream leech, ranshorn snail, damsefly nymph, Hong Kong newt and reservoir snail. Viviparous snail and ranshorn snail are the dominant species in site B, 12 of each of which can be found. For the other species, only 1-3 of which can be found.
Reasons why site A has larger number of each species while site B has greater diversity of organisms At site A, the phosphate content in the water is much higher than that at site B due to inorganic fertilizer used by farmers nearbyand slow water flow rate. Phosphate accumulates. The high phosphate content favours the growth of photoplankton. The slippery stone surfaces indicate the large population of photoplankton. The animal found in site A is mainly snails, a kind of filter feeder which feeds on photoplankton. As there is plenty of food, the growth of snail population is favoured.
The huge canopy of a tree covers the surface of the stream, reducing light intensity reaching the stream. The fallen leaves of a tree increase the nutrients available in the stream since they can be decomposed, releasing ammonia and phosphate. The physical environment in these 2 sites are different because:
3. The roots of the trees anchor the soil particles tightly, preventing soil erosion. 4. Mosses can secrete acid, breaking down large rocks into smaller soil particles. 5. When the dead bodies of living organisms such as insects decompose, it leads to an increase in nutrients available in the stream.
Reflections from polluted area Water in polluted area is smelly, turbid and still. A lot of rubbish can be found, such as tyres, glass, plastic bottles and suspended organic substances. The government should construct sewage pipes to collect and treat household sewage before discharge. People lack awareness of environmental protection that should be raised by the government through education. The government should set up laws and impose heavy fines on those who discharge untreated sewage into rivers directly.
Limitations of this field study • Time of investigation Since the investigation in this field study only covers a particular season(namely, winter), we are not allowed to obtain a full picture of the ecology of the two sites(site A and site B) throughout the year and we may not understand the whole thing thoroughly. For instance, a certain kind of organism may be active in summer, but not in winter.
Lack of sophisticated apparatus and skills to use them Since we do not have sophisticated apparatus and the skills to use them, some factors and organisms of the field cannot be studied. For instance, we cannot count the number of micro-organisms, such as bacteria and fungi in the stream and we cannot study them thoroughly. • Changing environment The reading varies from time to time shows that the environment is changing.
Conclusion After this field study, we can see that the organisms and the environment are interacting with each other continuously and form a stable ecosystem. For instance, the canopies of the tree affects the light intensity on the water surface and at the bottom, thus affecting the organisms. Moreover, human activity has adverse effect on the ecosystem. For example, household sewage directly discharged into the stream and the dumped inorganic fertilisers increase the phosphate content in water.
Improvements 1) For constrasting sites,we should avoid choosing somewhere just near other groups ,e.g. a bit lower position so the results will not be so easier affected by other groups' working. 2) We should have a better group coordination before collecting data at the stream and doing experiments in order to a better job allocation. 3) We should have more preparation e.g. finding more information about organisms in stream and the ways to proper use of apparatus before going the field trip.
Our feedback We are glad that we learn many things and gain many valuable experiences from this field trip. Firstly, it a great chance for us to contact with nature. We know more about the ecosystem of stream. We can also practise some skills learning from books. Moreover, we can use many modern apparatus which are not available in school laboratory. The trip also help us to know our weaknesses---poor job allocation and presentation skills. To improve this situation, we will try the best to have a better communication and have a rehearsal before presentation. All in all , the trip help us in both academic and personality development. It's a precious memory for us.
It is the first time for us to see a Hong Kong Newt . Every one of us actively participated in the Field Study to collect data and samples.
