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L10: Productivity & Thermal Stratification - Coggle Diagram
L10: Productivity & Thermal Stratification
Stratification
Summer
Layers
Epilimnion
Homogenous
Warm
Metalimnion
Thermocline
Hypolimnion
Homogenous
Cool (densest @ 4 degrees Celcius)
Turnover
Monomictic
Dimictic
Mixing causes change in temp
Only way for nutrients in hypolimnion to go back to epilimnion.
Fall
Destratification
↓ temp
↑ winds
Epilimnion pushed deeper
↓ density differentiation
Less temp variation within column
Spring
↑ winds = ↑ mixing
winds eventually slow down
↓ mixing, ↑ temp = ↓ dense
Air temp gradually ↑
Winter
No ice
Mixing continues
Monomictic (mixing from fall → spring)
Ice
Causes stratification
Prevents wind mixing
Forms thermocline
Dimictic (mix in fall and spring
Fish can still move @ 4 degrees
Lake Zonation
Littoral zone
Extends to rooted vegetation
↑ erosion
Coarse sediments
Fine sediments pulled away
High temp variation
↑ light, ↑ plant growth, ↑ leaf litter
↑ refuge
Good for rearing
Pelagic zone
Open water (surface)
↑ light and photosynthesis
↑ O2
no macrophytes
Rearing area for planktivourous fish
Profundal zone
includes benthic zone (habitat aspect)
Soft, muddy
↓ temp (4 deg)
↑ decomp
Anoxic
Dead zone
Leaf litter settle here
Benthic fish can spawn if O2 is enough
Productivity
Lakes age
Affects productivity levels (i.e trophic status)
Anthropogenic effects speed aging
Oligotrophic
Young & deep (except Lake Baikal)
Nutrient poot
Not enough time for mineral accumulation
↓ detritus
↑ O2
↓ phytoplankton, fish & zooplankton
small epilimnion : hypolimnion
Hypolimnion is well oxygenated all year
Good for salmon!
O2 is fairly constant cuz ↑ mixing
Eutrophic
Old and shallow
Nutrient rich
Older mountains
↑ phytoplankton & plants
↑↑ littoral
Small hypolimnion : epilimnion
Hypolimnion is anoxic in the summer
↑ decomp strips O2
not good for salmon
Interior BC
Aging sped up by anthropogenic factors
Cultural eutrophication
↑ nutrients from runoff
↑ primary productivity
↑ decomp
↑ hypoxia/anoxia
Dead zones
Lake Erie
↑ [O2]