Directly lethal = “thermal shock”.
Happens with any drastic temperature change, as when a plant begins operation
or shuts down.
Upper lethal temperature limit - chronic
effects of heat burden can kill or shorten life spans.
a) Cerio-daphnia: Lives for 108
days at 46 degrees F; lives only 29 days at 82 degrees F.
b) Larger species (fish) even less tolerant.
Reproductive and growth effects = temperature-dependent
reproductive cues like spawning (mollusks--hours after certain temperature
is reached) and hatching (aquatic insects).
Migratory patterns. Areas of elevated
temperature may act as a barrier for some species, particularly migratory
Distribution of species. Warmer water
is lighter and generally floats on colder denser water and can affect surface-dwelling
species directly or act as a barrier.
Cell permeability. Temperature will
affect permeability of an organisms cells, potentially affecting salt balance
as well as toxic chemical penetration/absorption. Available data
have indicated that toxicity increases with temperature.
Photosynthetic Respiration rates increase.
Lower dissolved oxygen because elevated temperature will cause water to
hold less oxygen causing respiration to double for each 10 degree C. rise.
Chemical reactions increase 2 to 5 times
faster for each 18 degrees F.
Significantly affects photosynthesis and
nitrogen fixation by blue-green algae contributing to Eutrophication.
Solubility of Oxygen decreases with higher
A carp can survive with as little as .5
ppm dissolved oxygen at 33 degrees F, but at 95 degrees, the requirement
is 1.5 ppm.
What is the recommended dissolved oxygen
for fresh water?