Transcript The External Features of the 2 Contrasting Regions

By CCC Kei Yuen College
Date of Fieldtrip :3-10-01 to 5-10-01
Contents
•
•
•
•
•
•
•
Objective
Introduction
Data
Examples of Organisms and their features
Data Analysis and interpretation
Food Web
Conclusion
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
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
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:
Distance across
stream(cm)
0
20
40
60
80
100 120 140
-6
-10 -16 -5
-3
-6
-5
-4
160 180 200 220 240 260 280 300 320 340 360
Depth(cm)
+34 +30
-17
-34
-35
380 400 420 440 460
-6
-5
-11
-15
-2
-8
-20
-16
-14
-4
-6
Station 2:
Distance across
stream(cm)
0
10
20
30
40
50
60
70
Depth(cm)
-31
-32
-17
-21
-26
-39
-37
-35
80
90
100 110 120 130 140 150 160 170 180
-40
-40
-44
-42
-49
-46
-43
-42
-47
-53
-43
190 200 210 220 230 240 250 260 270 280 290
-50
-56
-52
-48
-48
-49
-50
-47
-52
-45
-32
PHYSICAL FACTORS:
1
Light
intensity
Above surface
57
48
Underneath surface
46
45
Bottom
44
39
Underneath surface
25.9
26.7
25.8
25.9
Bottom
25.7
25.8
Surface
0.6
0
Mid-depth
0.4
0
Bottom
0.2
0
(Unit in scale A)
Temperature Mid-depth
(`C)
Current
speed
2
(m/s)
CHEMICAL FACTORS:
1
2
pH
5.3
5.6
Dissolved Oxygen(p.p.m.)
4.5
4.9
Phosphate Content(p.p.m.)
1.1
1.6
Ammonia Content(p.p.m.)
0.3872
0.2178
Conductivity(umhos)
12
25
Total Suspended Solids
(p.p.m.)
Non-measurable Non-measurable
Freshwater Plants
Abundance
Station 1
Station 2
Type
Alocasia odora
(Alocasia)
Callitriche stagnalis
(Water starwort)
Colocasia esculenta
Commelina nudiflora
(Day Flower)
Hydrilla verticallata
(Water weed)
Hydrodictyon reticulatum
Lemma minor
(Lesser duckweed)
Ludwigia adscendens
(Water dragon)
FO
Adaptive
Features
Polygonum hydropiper
(Water dragon)
Sagittaria sagittifolia
Spirodela polyrhiza
(Greater duckweed)
Spirogyra sp.
Wolffia arrhiza
(Water meal)
WS
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 :
Code
Type
Description
WS
Waterside
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
PF
Rooted in stream bed,m
These plants have most of their
but with protruding foliage foliage above water
FF
Rooted in stream bed, with These plants have most of their
floating foliage
foliage in water
CS
Rooted in stream bed and completely These are often quite small
submerged
plants growing on the bottom
FI
Floating freely in water
These plants are floating in
water and not rooted.
FO
Floating freely on water
These plants are not associated
with the sea bed at all and have
roots dangling in the water .
AL
Algae
At any one time , a particular
species of alga may be very
abundant, forming an algae
‘bloom’.
Freshwater Animal
Location*
Number
Station 1 Station 2
Mayfly nymph
UR
Stonefly nymph
UR
Damselfly nymph
UR
Dragonfly nymph
Caddisfly larva
UR
Alderfly larva
UR
Water penny
Mosquito larva
Mosquito pupa
Adaptive
Features
Freshwater Animal
Location*
Number
Station 1 Station 2
Water skater
OS
Water cricket
Water measurer
Water beetle
Water boatman
Water stickinsect
Blackfly larva
Large stream snail
Reservoir snail
UR
Adaptive
Features
Freshwater Animal
Location*
Number
Station 1 Station 2
Common freshwater shrimp
OB
Long-armed shrimp
OB
Adaptive
Features
Freshwater crab
Goby
OB
Mosquito fish
Guppy
Loach
OB
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
EXAMPLES:
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
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
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
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
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
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
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
BACK
Slow running water
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).
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
The External Features of the 2
Contrasting Regions
Still water
1.Current speed
2.Clearness
3.Depth
4.Structure
5.Presence of
leaf litter
6.Presence of
algae
slow
lower
deeper
stones &
clay/mud
more
present
Fast running
water
fast
higher
shallower
mainly rocks
less
absent
Difference of number & types of
organisms
Still water
Fast running
water
Number of
organisms
increase
decrease
Types of
organisms
increase
decrease
(e.g.water skater) (e.g.mayfly
nymph)
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
Relationship between distribution
of organisms & physical factors
Nature of
stream
bottom
Still water
Fast running water
*Stone & slit
 fine particles and
organic debris would stay
distribution
*mainly rocky
 lighter & smaller
particles can pass away
distribution
Water depth *deeperlight intensity 
& light
intensity
Stream width *broadercurrent speed 
& current
speed
*shallow light intensity 
(light intensity is not a
limiting factor)
*narrowercurrent
speed
( inter-related)
BACK
Crabs
Small fishes
Shrimps
BACK
Snails Mayfly nymph
Algae
Caddisfly larvae
Organic debris
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.
BACK