Freshwater ecosystems Flashcards
What influences the salinity of lakes?
River inputs
Give two examples of characteristics of large lakes
They are old and have significant numbers of endemic biota
Give five qualities that can vary between lakes
Size, volume, age, salinity, and trophic status
Describe eutrophic lakes
Shallow lowland lakes with high nutrient input, low light penetration, and high primary and secondary productivity. In a disturbed or naturally fertile catchment area
Describe mesotrophic lakes
Intermediate between eutrophic and oligotrophic
Describe oligotrophic lakes
Deep mountain lakes with low nutrient contents, high light penetration and low biomass, primary and secondary productivity. Found in infertile and undisturbed catchment areas.
What happens to lake water temperatures in the lake spring?
Solar and wind energy produce localised surface heating in the epilimnion. There is circulation and retention of warmth at the surface.
What does the late spring warming of the epilimnion result in?
High primary production in the epilimnion with low inorganic content (leads to limited bloom) and no primary production in the hypolimnion with high nutrient content
What processes occur in the hypolimnion?
Anaerobic decomposition. The hypolimnion influences the movement of N and P.
Describe lake water in the spring
The is no surface warming, stratification, or variation in dissolved oxygen. Often windy, leading to wind-induced mixing.
Describe lake water in the summer
Reduced wind-inducing mixing, leading to stratification. Surface warming
What can also be affected by seasonality?
Phytoplankton primary production
In what seasons does phytoplankton primary production increase?
Late summer and spring
In what seasons does phytoplankton primary production decrease?
Early summer clear water (CW) phase and autumn
Why is there low phytoplankton primary production in winter?
There is low light and temperature
