Effects of Water Flow Speed on the Abundance of Individuals of - - PowerPoint PPT Presentation

Effects of Water Flow Speed

• n the Abundance of

Individuals of Animal Species

Ko Chin Wa Tsang Faan Ho Wong Hin Ching

Variables

• Independent variable - speed of water flow
• Dependent variable - abundance of individuals of

animal species

• Controlled variables - water depth (shallow), river

bed substrate composition (pebbles and small stones), time for sampling at each location (approximately 20 minutes), number of people sampling (2)

Hypothesis

• Number of individuals
• rises for slowly flowing water, until the optimum flow

speed is reached, then the number of individuals starts to fall for fast flowing water.

Materials and Methods

• Designate three shallow regions (for easier sampling) that have roughly

the same river bed substrate composition (pebbles and small stones) with different water flow rates.

• A water flow meter - measure the water flow speed
• A stop watch - measure the time for collecting samples and ensure a fair

test by using the same time at each location

• A 0.5m x 0.5m quadrat - sample as many animal species within the

boundary of the quadrat as possible, within 20 minutes

• Pick up the stones to see any hidden species
• Identify the species and make a table for counting the number of

individuals

Results

Results

3 6 9 12 Still water (~0 m / s Moderately flowing water (~0.02 m / s) Fast flowing water (~0.18 m / s) Blue - Viviparous Snail Green - Water Skater Yellow - Water Penny Red - Damselfly Nymph Purple - Mayfly Nymph Orange - Dragonfly Nymph

Still water

Water flowing at moderate speed

Fast flowing water

Analysis and Summary

• Water flow speed rises for slowly flowing water
• Still water has no appreciable current
• Oxygen concentration is low
• Water turbidity is high
• Limited source of nutrients
• A rise of water flow rate leads to better environment

for survival

Analysis and Summary

• The number of individuals reach a peak at optimum

water flow rate

• Usually saturated with oxygen
• More available food

Analysis and Summary

• Number of individuals of not-so-adaptive species

start to fall

• Species having developed adaptive features, e.g.

viviparous snail, for fast running water will benefit from less severe interspecific competition and have a much larger number of individuals