Download Lake Zonation by Biological Production

Lake Zonation by Biological
Production of Organic Matter
MP 2.3
Oligotrophic Lakes
• Low productivity with a small
surface area compared to depth
• Little decomposition because it is
so cold so oxygen is plentiful
• Bottom sediments low in
decomposable material (detritus)
• Shortage of nutrients limits
photosynthesis
• Very clear water
Eutrophic Lakes
• Nutrient-rich have a small
surface area compared to
depth
• Have much detritus on the
bottom that supports high
rates of photosynthesis.
• High decomposition rate
uses up much of the oxygen
in the pond.
Mesotrophic Lakes
• Have an intermediate level
of productivity, less than
eutrophic but more than
oligotrophic lakes.
Stream Ecology
MP 2.4
Streams and Rivers
• Defined is a body of water that
is moving continuously in one
direction
• At the headwaters the water is
usually cold and clear (except
for glacier streams) with little
minerals or nutrients
• Rivers pick up minerals and
nutrients as they head
downstream.
Turbidity
• Becomes more and more
turbid (carrying sediment)
downstream
• There is a frequently a visible
line where a clear stream
enters a turbid one (or vice
versa), called the line of
turbidity
• Turbulence stirs up water
adding oxygen, slow flowing
rivers have less oxygen
Animal
Adaptations
• Animals that live in and
around rivers have
evolved hydrodynamic
body shapes to handle
current or live on the
downstream side of rocks.
Point Source Pollution
• Rivers have been a dumping ground for
pollutants for centuries because they
carry it away from the local area
• Downstream in a river system pollution
accumulates increasing as it moves
toward the sea.
Water Quality
• Ecologists measure
water quality by
counting the diversity
of invertebrates
• The better the water
quality the greater the
invertebrate species
richness (number of
species)