Chapter 7 - Dissolved Oxygen Flashcards
Dissolved oxygen (DO)
The amount of oxygen present in the water.
What kind of water system has the greatest amount of DO?
Rapid moving water, like streams and large rivers
What makes a eutrophic situation?
Bacteria in the water (along with plants and algae via respiration) consume oxygen as organic matter decays, and excess organic matter can cause an oxygen-deficient situation
What is the partial pressure of oxygen?
.2095 atm (know for Henry’s law)
What is the daily change of dissolved oxygen?
During dark hours of the day (like midnight) DO levels are at a minimum because respiration dominates. However, during sunny hours of the day (like noon) DO levels are at a maximum because photosynthesis is dominating within the system.
What does DO concentration look like during the different seasons?
DO concentrations are higher in the colder months because cold water can hold more DO than warmer water can.
What is the effect of temperature and salinity on DO concentrations?
As temperature increases, DO decreases. As salinity increases, DO decreases
What are some ways we can quantify DO?
We can measure DO by using an optical dissolved oxygen meter. Spectrophotometric methods are also used to quantify DO.
Dead zones
Oxygen depletion begins in the late spring, increases in the summer, and ends in the fall
The story of hypoxia
- Overland runoff and water from rivers enter the lake, bringing organic matter and nutrients. 2. Nutrients allow plankton to flourish. 3. Plankton produce oxygen via photosynthesis. 4. Oxygen from the atmosphere enters top layer of water via wind/wave mixing. 5. Movement of water and oxygen are halted at thermocline. 6. Plankton die and produce waste. Dead cells, waste products, and other organic matter sink to the bottom. 7. Dead cells, waste and organic matter are decomposed and oxygen is consumed. 8. Organisms that can not tolerate or escape hypoxia die. 9. Some animals are able to escape to oxygenated water
