Dissolved Oxygen: What Fish Need

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Dissolved OxygenWhat Fish Need

• Jeff Bennett
• Sean Hazlett
• Alex Higgins

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What Fish Need

• Dissolved Oxygen gas in water (DO) is vital to
  the existence of most aquatic organisms
• Key component in Cellular Respiration
• Important indicator of the environments water
  quality
• Level of DO determines what organisms can live
  there
• Factors that determine DO concentration
  Temperaturte, stream flow, air pressure, and
  human activities
• DO levels fluctuate daily as a result of plant
  activity
• Because of this, you must test levels at the same
  time each day

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Dissolved Oxygen FactsChemical/Biological/Physic
al

• Measured in mg/L
• Dissolved By
• Diffuses from Atmosphere
• Aeration as water moves over rocks/debris
• Aeration from wind/waves
• Photosynthesis of aquatic plants
• Unit mg/L which is quantity of gas in 1 Liter
  of water

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Expectations
Organism Minimum DO Trout 6.5
(mg/L) Smallmouth Bass 6.5 Caddisfly
larvae 4.0 Mayfly larvae 4.0 Catfish 2.5 Carp
2.0 Mosquito larvae 1.0

• Average DO range 0 15mg/L
• Cold mountain stream average 2 11mg/L
• Low reaching DO range 2 11 mg/L

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Past Data

• Average DO ranged between 9.6-10.3mg/L
• Temperature in (Fahrenheit) of samples- A 18.1
  B18
• Atmospheric pressure (752 mmHg) for each sample
• 100 dissolved oxygen(7.83mg/L) each sample
• Percent saturation- A 131.5 B122.6

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Method for Determination

• Prepare the DO Probe for use
• Unscrew membrane cap from the tip of the probe
• Using a pipet, fill the membrane cap with 1mL of
  DO electrode Filling Solution
• Carefully thread the membrane cap back onto the
  electrode
• Place the probe into a container of water

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Setting up calibration

• Connect the dissolved oxygen probe to LabQuest
  and choose New from the File menu. If you have an
  older sensor that does not auto-ID, manually set
  up the sensor.
• Warm the Dissolved Oxygen Probe for 5-10 minutes
  before taking readings.

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Setting up Calibration
On the meter screen, tap Mode. Change data
collection mode to Selected Events. Select
Average over 10 seconds and select OK. If your
instructor directs you to manually enter the
calibration values choose Calibrate from the
Sensors menu and tap Equation. Enter the
values for slope and the Intercept then select
apply
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Calibration and Data Collection
Start data collection Rinse the tip of the probe
with a sample of water Place the probe into the
stream at site 1, or into a cup with sample
water Wait for the live DO readings to
stabilize Tap Keep to collect the first data
pair. IMPORTANT- Leave the probe tip submerged
while data is collected for 10 seconds. Repeat
for sample 2 Tap Table to view the data. Record
the averaged Do values for readings 1 and 2

• Calibrate either using the zero-oxygen
  calibration point or the saturated DO calibration
  point

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Safety Concerns and Equipment
Equipment Labquest LabQuest
App Vernier Dissolved Oxygen Probe 250mL
Beaker Sodium Sulfite Calibration Solution DO
Electrode Filling Solution 100 Calibration
Bottle Pipet Distilled Water

• Safety Concerns
• Always Wear Goggles
• Wear gloves when you handle chemicals used to
  measure DO

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Concerns for reliability of results
How to read the Data Read the saturation and
compare to current water quality graph from
expected result slide.

• Make sure there are no air bubbles in the water
  sample.
• Keep the sample from being agitated when
  collected.
• Take a sample away from the edge of the water
  source and do not agitate the soil in any way.

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5 Question Quiz

• DO is a key component of ____ for aquatic/
  terrestrial life
• What unit is used to measure DO?
• T/F- DO levels fluctuate throughout the day and
  so you must perform the tests at the same time
  each day.
• What is the average range for DO mesurements?
• How long should you allow for the DO probe to
  warm up before use?