Quiz 2 Lecture 3 Flashcards
(44 cards)
What is dissolved oxygen?
Dissolved Oxygen (DO) refers to the O2
dissolved in water, expressed as mg/L or mol/L or percentage saturation
What is percentage saturation?
is concentration of O2 relative to maximum at equilibrium concentration
for that solution
DO is a function of what factors and how?
- Temperature - solubility of O decreases as T increases
- Pressure - solubility of O increases as P increases (related to altitude)
- Salinity - solubility of O decreases as S increases
What happens to DO as temperature increases?
The DO decreases
What is supersaturation?
DO concentration above
saturation. Will form O2 bubbles and come out of
solution
What is sub saturation?
Is DO concentration below saturation
What are oxic/aerobic conditions?
O2 present in the water
What are anoxic or anerobic conditions?
No O2 present in the
water
At high temp and high altitude what conc of O do we see?
the lowest DO
Do At low temp and low altitude?
see highest DO
What are the oxygen sources for water?
The atmosphere- amount depends on diffusion and turbulence (some of it)
Photosynthesis (most of it)
Why does oxygen from atmosphere source depend on diffusion and turbulence?
Because oxygen can get diffused at surface, alot of wind will bring turbulence and introduce oxygen in there
What are the oxygen sinks? (3)
Diffusion to atmosphere
Respiration
Chemical oxidation (happens in hypolimnion, cold bottom of lake, where no photosynthesis)
In an ocean what zone has the most photosynthesis oxygen production?
In photic zone where light penetrates and littoral zone
What are orthograde lakes DO and temp patterns? Why? What are orthograde lakes mainly guided by?
The oxygen doesn’t change much, is littler in epilimnion, gets slightly higher in hypolimnion. Because it’s warmer at the top, and the system is not that productive at the top. Mainly guided by temperature effecting solubuiloty of O
What are clinograde lakes DO and temp patterns? Why? What are clinogrades lakes mainly guided by?
Oxygen and temp high at surface, and then decrease lower down. This is because there’s high productivity at the top, they then die and sediment and respirate which causes more respiration and decreases DO at bottom. This is mainly driven by photosynthesis.
What are heterograde lakes DO and temp patterns? Why? What are heterograde lakes mainly guided by?
See big peak in oxygen at top of metalimnion and big dip at bottom of metalimnion. This is because at the top of the metalimnion there’s a lot of productivity, then have big organisms at the bottom of metalimnion that act as a sink for oxygen, organisms can’t move due to density and will trap zoo plankton in low metalimnion and plants at the top of metalimnion. Overall oxygen increases as temp decreases.
What are anamolous lakes DO and temp patterns? Why? What are anamolous lakes mainly guided by?
See peak of oxygen at the top of the hypolimnion, this can be due to inflow of water- see big pocket, or odd shape of lake
What are the seasonal pattern of DOs in a dimictic oligotrophic lake?
In a typical dimictic lake (mixes fall and spring, and is low productivity (oligotrophic), in spring temp consistent throughout whole water column and oxygen also mixing throughout column
Summer stratification- have oxygen lower at surface and higher at bottom due to increased temp at top due to thermal stratification.
Fall turnover- same thing happens as spring
Winter stratification- have ice cover, see slightly colder at surface and slightly warmer lower down, therefore see slightly high oxygen at surface and slightly lower at bottom
What are the seasonal pattern of DOs in a dimictic eutrophic lake?
same in spring turnover, in summer, oxygen starts off highish but then goes off to 0 in hypolimnion, due to a lot of productivity- the hypolimnion has a lot of respiration and decomp.
During fall turnover is same, and then in winter stratification the oxygen start off high and then dips in hypolimnion, this is due to have organisms use up oxygen there, ice cover decreases photosynthesis, diffusion, and turbulence. Biological activity uses up oxygen.
What is fish winterkill?
This happens when there’s no oxygen due to ice cover, so fishes die and we see them at surface.
horizontal line indicates what in an oxygen curve?
stratification
What is summer kill?
When it gets really warm, don’t have oxygen near surface but increased productivity, however increased productivity gets oxygen used up in the bottom and fish die.
How do diurnal changes effect stream base don their initial productivity?
In oligotrophic system, the oxygen dips slightly during night and have more photosynthesis so more oxygen in day but very slightly, however in eutrophic system this change is much more.
