lec 4

Question 1

what is viscosity? what is it caused by?

Answer 1

viscosity is the ability for a liquid to stick to itself. water has strong bonds so it is fairly ‘sticky.’

temperature affects viscosity since bonds can be weakened (high temp) or strengthened (low temps)

Question 2

what da fuck is a boundary layer

Answer 2

near surfaces, there is a thin layer of water that ‘sticks’ due to adhesion and friction and other forces. boundary layers are mostly characterized by slower movement.

Question 3

what is surface tension? what are its implications for animals/environ? what is the relationship bw surface tension and the air?

Answer 3

u know when water pour water into a cup and u can pour a little more than the cup should be able to hold bc it makes that bulge. thats surface tension

organisms such as water striders adapt this for walking on water

SURFACE TENSION CREATES BOUNDARY LAYERS BETWEEN AIR AND WATER!!

Question 4

what is PAR?

Answer 4

PAR stands for Photosynthetically Active Radiation - it is the spectrum of light that can be used for photosynth, spanning the visible light spectrum

Question 5

why is water blue?

Answer 5

visible light spectrum spans ~400 - 700 nm. red is on the higher nm side, while blues are on lower nm side. higher nm = higher energy –> can’t make it as deep

Question 6

what is incident radiation? what can affect it? (hint: 4 factors)

Answer 6

solar radiation hitting something (in our cases, bodies of water).

incident radiation can be affected by lattitude, time of year (season), cloud cover, ice/snow cover

note: WHITE ice cover (slow freeze) reflects light but BLACK ice cover (flash freeze) does not reflect light.

Question 7

what affects the degree to which light penetrates water? (4 things)

how do oligotrophic and eutrophic lakes compare in terms of light penetration?

Answer 7

• absorption through the water column (determined by a constant, depending on the body of water)
• absorption of light by dissolved organic matter/dissolved organic carbon (DOM/DOC, respectively)
• absorption by organic matter (ex. algae, cyanobacteria, plants, etc)
• scattering by inorganic particles (silt, clay, etc)

since they have little nutrients and few prim prods, oligo- are typically quite clear (lot of penetration). conversely, since eutroph- tend to have lots of nutrients and many prim prods, they are typically quite cloudy (little penetration)