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By CCC Kei Yuen College Date of Fieldtrip :3-10-01 to 5-10-01.

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Presentation on theme: "By CCC Kei Yuen College Date of Fieldtrip :3-10-01 to 5-10-01."— Presentation transcript:

1 By CCC Kei Yuen College Date of Fieldtrip : to

2 Contents Objective Introduction Data Examples of Organisms and their features Data Analysis and interpretation Food Web Conclusion

3 Objective 1. To understand the structure and functioning of a freshwater stream ecosystem. 2. To learn and practice basic techniques in freshwater ecological studies. 3. To measure environmental factors of freshwater stream with simple field equipment. 4. To identify common freshwater organisms. 5. To study the distribution of freshwater organisms and their relationship with the environment. 6. To identify and interpret adaptive features of freshwater organisms. BACK

4 Introduction Our field site is Ho Chung. We are going to focus on both physical and biotic factors. Besides these, we observe, search and identify the organisms present by using keys and reference books. Let’s take a closer look into our field site -- Ho Chung. BACK

5 Brief Description of Stations Station 1: Fast-running water stream Station 2: Still water stream Construct cross sectional profiles of station 1& station 2 by using the following data Station 1: Depth(cm) Distance across stream(cm)

6 Station 2: Depth(cm) Distance across stream(cm)

7 PHYSICAL FACTORS: 00.2 Bottom 00.4 Mid-depth 00.6 Surface Current speed (m/s) Bottom Mid-depth Underneath surface Temperature (`C) 3944 Bottom 4546 Underneath surface 4857 Above surface Light intensity (Unit in scale A) 21

8 CHEMICAL FACTORS: Total Suspended Solids (p.p.m.) 2512 Conductivity(umhos) Ammonia Content(p.p.m.) Phosphate Content(p.p.m.) Dissolved Oxygen(p.p.m.) pH 21 Non-measurable

9 Adaptive Features Type Station 2 Abundance Station 1 Freshwater Plants Ludwigia adscendens (Water dragon) Lemma minor (Lesser duckweed) Hydrodictyon reticulatum Hydrilla verticallata (Water weed) Commelina nudiflora (Day Flower) Colocasia esculenta Callitriche stagnalis (Water starwort) Alocasia odora (Alocasia) FO

10 Wolffia arrhiza (Water meal) Spirogyra sp. Spirodela polyrhiza (Greater duckweed) Sagittaria sagittifolia Polygonum hydropiper (Water dragon) WS

11 keys 1 ~Microhabitats of freshwater plants Freshwater plants are typically grouped according to their habitat and in where the plant organs grow.The usual divisions are as follows : These plants have most of their foliage in water Rooted in stream bed, with floating foliage FF These plants have most of their foliage above water Rooted in stream bed,m but with protruding foliage PF These plants grow at the side of the water or else are rooted in the shallow water at the edge, but have all or most of their foliage protruding aerially WatersideWS DescriptionTypeCode

12 At any one time, a particular species of alga may be very abundant, forming an algae ‘bloom’. AlgaeAL These plants are not associated with the sea bed at all and have roots dangling in the water. Floating freely on waterFO These plants are floating in water and not rooted. Floating freely in waterFI These are often quite small plants growing on the bottom Rooted in stream bed and completely submerged CS

13 Mosquito larva Number Mosquito pupa Water penny UR Alderfly larva UR Caddisfly larva Dragonfly nymph UR Damselfly nymph UR Stonefly nymph UR Mayfly nymph Adaptive Features Station 2Station 1 Location* Freshwater Animal

14 UR Reservoir snail Large stream snail Blackfly larva Water stickinsect Water boatman Water beetle Water measurer Water cricket OS Water skater Station 2Station 1 Adaptive Features NumberLocation*Freshwater Animal

15 OB Loach Guppy Mosquito fish OB Goby Freshwater crab OB Long-armed shrimp OB Common freshwater shrimp Station 2Station 1 Adaptive Features NumberLocation*Freshwater Animal key2 of locations: OS-on water surface UR-under rock BS-hanging below water surface SE-in bottom sediments FS-free swimming AP-among plants OB-on bottom BACK

16 Sand tube caddifly larva case formed by sand graibns stuck together, can effectively protect the larva ~~( 1 cm ) Ecological Information : Carnivore Benthos Have cryptic colour Uncommon In clean water Slow running water EXAMPLES:

17 Mayfly nymph Flattened body for hiding under rocks. Strong legs for holding itself firmly on rock surface. Lateral abdominal gills for gaseous exchange. Ecological information: Herbivore Detritivore Benthos Cryptic colour Very common In clean water Fast running water Slow running water

18 Common Freshwater shrimp Chelate walking legs for holding food (~1.5 cm) Ecological information: Omnivore Cryptic colour Scavenger Benthos Common In clean water Slow running water

19 Small Long-armed shrimp Large chelate walking leg for dafencce against enemies(~5 cm) Ecological information: Omnivore Benthos Cryptic colour Common In clean water Slow running water

20 Stream Loach Expanded pectoral & pelvic fins lying in a horizontal plane, likes suckers. Ecological information: Benthos Carnivore Detritivore Cryptic colour Very common In clean water Fast & slow running water

21 Freshwater Goby Pelvis fins united into an oval disc Ecological information: Carnivore Benthos Cryptic colour Very common Fast & slow running water In clean water & slightly polluted water

22 Water skater Extremely long leds for keeping the body away from the water surface. Leg’s surface covered with bristle which keeps the body floating by the effect if water tension. Ecological information: Scavenger Neuston Cryptic colour Very common In the clean water Slow running water BACK

23 Is the stream productive? Support your opinion with evidence. The stream is productive. Since energy is enough to support third trophic level according to the food-wed (from producer to tertiary consumer).

24 What are the sources of energy and matter for the stream ecosystem? To keep a balance ecosystem, energy and matter are required : Main source of energy :solar energy (from sunlight) Main source of matter : leaf litter chumus

25 The External Features of the 2 Contrasting Regions Still waterFast running water 1.Current speedslowfast 2.Clearnesslowerhigher 3.Depthdeepershallower 4.Structurestones & clay/mud mainly rocks 5.Presence of leaf litter moreless 6.Presence of algae presentabsent

26 Difference of number & types of organisms Still waterFast running water Number of organisms increasedecrease Types of organisms increase (e.g.water skater) decrease (e.g.mayfly nymph)

27 Interpretation It depends on either good adaptive features or adequate nutrients e.g.Mayfly nymph~with 3 tail filaments~for attachment e.g.Water skater ~still water has high enough water surface tension~for movement

28 Relationship between distribution of organisms & physical factors Still waterFast running water Nature of stream bottom *Stone & slit  fine particles and organic debris would stay  distribution  *mainly rocky  lighter & smaller particles can pass away  distribution  Water depth & light intensity *deeper  light intensity  *shallow  light intensity  (  light intensity is not a limiting factor) Stream width & current speed *broader  current speed  *narrower  current speed  (  inter-related) BACK

29 Crabs Small fishes Shrimps Snails Mayfly nymph Caddisfly larvae AlgaeOrganic debris BACK

30 Conclusion We have learnt how to identity common freshwater organisms and the adaptive features of the organisms. Also, we have learnt and practiced basic techniques in freshwater stream ecosystem by measuring environmental factors of freshwater stream with simple field equipment.More important, we have understood the structure and functioning of a freshwater stream ecosystem and the distribution of freshwater organisms and their relationship with the environment.

31 BACK


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