I'm Breathing Here!
How do wind and waves help add oxygen?
They mix air into the surface water
The water has a pH of 8, salinity of 12 ppt, and turbidity of 2 NTU. What’s wrong?
The salinity is too low, being much less salty than 35 ppt
What is the desired pH for our species?
About 8.1
Does BOD tell you how much oxygen is in the water right now? Or is that DO?
DO tells the oxygen right now. (BOD tells how much oxygen will be used)
The term for the concentration of dissolved salts in a body of water
Salinity
What does “Anoxic” mean?
A complete absence of dissolved oxygen
Seaweed lives in water with a pH of 8.3, salinity of 37 ppt, dissolved oxygen of 7 mg/L, and turbidity of 40 NTU. Is it in trouble? Why?
The turbidity is too high. 40 NTU is very cloudy, and much over 1–5 NTU
What is the required salinity for our species?
~ 35 ppt
Why is the BOD test done in the dark?
So photosynthesis doesn’t add more oxygen during the test
The term for the concentration of hydrogen ions (H⁺) in a solution
pH (it means "power of hydrogen”)
If salinity goes up, can the water hold more, less, or the same amount of oxygen?
The water holds less oxygen
The water has a pH of 7.9, salinity of 33 ppt, dissolved oxygen of 1.4 mg/L, and turbidity of 2 NTU. What is wrong, if anything?
The dissolved oxygen is too low, being hypoxic, much under 6–8 mg/L
What is the required range for Turbidity in a reef?
1–5 NTU
A bloom dies and sinks. What happens to the BOD?
BOD goes way up because bacteria have more dead material to break down
If I say “that’s basic,” what does that mean in this context?
A pH value greater than 7 (a low concentration of hydrogen ions)
Does colder water hold more or less oxygen than hot water? Why?
More, because in cold water molecules move slower, making it easier for oxygen to stay trapped
The water has a pH of 8.1, salinity of 35 ppt, dissolved oxygen of 8 mg/L, turbidity of 3 NTU, and BOD₅ of 1 mg/L. What is wrong, if anything?
Nothing is wrong, all five are within their healthy ranges
Healthy estuary Biochemical Oxygen Demand (BOD) is usually about what range?
1–4 mg/L
Why do you dilute a sample before a BOD test?
So the bacteria don’t use up all the oxygen before the 5 days are over. (not diluting -> more food -> using up more oxygen)
NTU is the unit for measuring what?
Turbidity (NTU = “Nephelometric Turbidity Unit”)
Bacteria start eating a lot of dead algae. Do dissolved oxygen levels go up, down, or stay the same?
DO goes down (as bacteria digest the dead algae they consume oxygen)
The water has a pH of 8.2, salinity of 34 ppt, turbidity of 3 NTU, dissolved oxygen of 6 mg/L, and BOD₅ of 6 mg/L. What’s wrong, if anything?
The Biochemical Oxygen Demand is too high, being outside of both the Estuary 1–4 mg/L and the Reef <1 mg/L
Healthy ocean / reef Dissolved Oxygen (DO) levels are usually about how many mg/L?
6–8 mg/L
What is one reason the same BOD is more dangerous in hot summers than in winter?
Higher temps 1) dramatically reduce the water's capacity to hold oxygen, and 2) speeds up how fast bacteria consume oxygen
What is the thing that takes 5 days at 20 °C in the dark?
The Biochemical Oxygen Demand (BOD₅) test