Biology Field Trip

1. Biology Field Trip Freshwater stream

2. Introduction • Field site location: Freshwater stream habitat at Ho Chung • Date: 10th May 2004 • Time: 1:00 pm – 4:00 pm • Weather: sunny, hot and windy

3. Physical factors • Light intensity • Temperature • Current speed

4. Light Intensity • In still water, there are many suspended solids and the turbidity is relatively high, which prevent the penetration of sunlight • In running water, the slope is steeper which limits the penetration of sunlight Result: the light intensity in the stagnant water is higher than that of the running water.

5. Temperature • In running water, rapid pool avoid and reflects sunlight from direct penetration • As light can only penetrate to a limited distance, so light intensity increases and temperature increases Result: the temperature in still water is higher than that of running water

6. Current Speed • The freshwater bed is not a smooth surface rock layer. • Rocks and sand sink to the freshwater bed. increases the contact area of water and the friction is present. • more rocks and sand, increases the friction of the water and thus the current speed decreases. • Gradient of freshwater bed is also a factor affecting the current speed, but it is not included in our investigation. Result: the current speed in running water is higher than that of still water

7. Chemical factors • pH value • Dissolved oxygen • Phosphate content • Ammonia content • Conductivity • Total suspended solids

8. pH value • Decomposer in muddy area of the station might cause decomposition at the pond bottom, lead to production Carbon dioxide(rocky in nature might not be suitable for decomposers to grow) • Erosion of minerals from stones and decomposition of detritus • Acid rain & carbon dioxide dissolved in water. Result: pH value in running water is higher than that of stagnant water ( both value are lower than 7)

9. Dissolved oxygen • Dissolved oxygen in running water is higher than in stagnant water. Since animal found in still Water current is more than in running water • Water current is faster in running water than in still water • Fast flow of water can replenish the oxygen content quickly • Result: more D.O. in running water

10. Phosphate content • The phosphate in stream is came from the erosion of the stone or came from fertilizers & detergent • Phosphate is washed away because the current speed of water is high Result: thus, still water contains more phosphate than running water (lower than the government standard)

11. Ammonia content • Comes from dead body of plants & animals & their metabolic wastes • as the current speed in running water is higher, it washes away the ammonia content, so it decreases Result: The ammonia content in still water is higher than that of running water

12. Conductivity • Due to the presence of charged ions from mineral concentration in still water , the decomposition and dilution effect decrease • Ions accumulated in slow current zone, so concentration of ions increases and the conductivity increases. Result: the conductivity of still water is higher than the running water.

13. Total suspended solids • The current speed of running water is high, so it washes away the suspended solids • The still water is muddy and also the human disturbance, so the current speed is slower and the solids remain at the slow current zone. Result: the suspended solids in still water is higher than running water

14. Adaptation of freshwater animals • Mayfly nymph • Goby • Blood Worm • Mosquito • Pond skater • Dragonfly Nymph • water cricket • Damselfly nymph • Water skater

15. Mayfly nymph • herbivores and detritivores • Flattened body & legs for dripping on to the surface of stones • have three ‘tails’ for possessing a long central filament • grow slowly • They are found in fast-moving water and slow-moving water Body Characteristics: • 5-28 mm long • 6 legs • gills present on the abdomen • 2 or 3 long thin “tails”

16. Mayfly nymph

17. Goby • Depressed head with a wide mouth • The mouth is large • Pelvic fins fused to form pseudosucker • It feeds on smaller fish, shrimps, insect larve, and aquatic insects • 10—14 cm in length.

18. Goby

19. Blood Worm • Red colour • Blood gills • Some have green blood Water skater • Long, thin legs • hair on legs • thin, flattened body

20. Water skater

21. Water cricket • strong & thick body • dark brown with 2 orange lines down the back • orange abdomen • About 2mm in length

22. Damselfly nymph • 3 terminal caudal gills • No rectal gills • Large, mask-like labium • More slender than dragonfly nymph

23. Damselfly

24. Dragonfly Nymph • pond species with long thin and rather delicate legs • opposed to the common torrent stream species • has a flatted body and stout flattened legs. • the mask is very large and can be seen covering the front of the face.

25. Dragonfly nymph

26. Dragonfly

27. Mosquito • large anterior ends formed by head and thorax • a part of plates at the end for swimming • Larva: bearing 9 abdominal segments • bearing and gill at the 9th segment • dark brown to black in colour • 6-9mm long

28. Conclusion From the investigation, we found out that the water is clean from all factors (lower than the government standard) Both water zone are scored for 2 marks • Learn different kinds of species • Physical and chemical factors in a habitat • There are interaction between matters • Protect our environment

29. ~The End~ From: Lingnan Hang Yee Memorial Secondary School