Limnology – 25 points – 5 for discussing each of the layers and 5 for the figure
Epilimnion- The uppermost layer of a lake. It generally has higher pH and higher O2 concentration than the hypolimnion.
Thermocline- Thin layer in which temperature changes more rapidly with depth than it does in the layers above or below
Hypolimnion- The dense, bottom layer of a lake. Typically the coldest layer during the summer, and warmest during winter.
Benthic- Lowest level of a lake, including the sediment surface and some sub-surface layers.
Epilimnion- The uppermost layer of a lake. It generally has higher pH and higher O2 concentration than the hypolimnion.
Thermocline- Thin layer in which temperature changes more rapidly with depth than it does in the layers above or below
Hypolimnion- The dense, bottom layer of a lake. Typically the coldest layer during the summer, and warmest during winter.
Benthic- Lowest level of a lake, including the sediment surface and some sub-surface layers.
Trophogenic Zone
-The upper layer of a lake where light permits photosynthesis.
-Organisms: Algae, swimming fish and insects, plankton, rotifers, microscopic crustaceans
Tropholytic Zone
-Lower layer of a lake where food is used faster than it is produced.
-Organisms: Bottom dwellers, bacteria, fungi
-The upper layer of a lake where light permits photosynthesis.
-Organisms: Algae, swimming fish and insects, plankton, rotifers, microscopic crustaceans
Tropholytic Zone
-Lower layer of a lake where food is used faster than it is produced.
-Organisms: Bottom dwellers, bacteria, fungi
Overturn
Summer- Temperature differences between layers increase to where the layers no longer mix
Fall- Cooler air temperatures cause the surface temperature to drop, allowing the layers to mix again, which also mixes nutrients and oxygen throughout the lake more evenly.
Winter- Temperature is about the same throughout the lake. Ice forms on the top layer, and if it grows thick enough, it can stop light coming through and halt photosynthesis.
Spring- The ice melts, and the lake mixes again. Rising temperatures then cause the lake to begin separating again.
Summer- Temperature differences between layers increase to where the layers no longer mix
Fall- Cooler air temperatures cause the surface temperature to drop, allowing the layers to mix again, which also mixes nutrients and oxygen throughout the lake more evenly.
Winter- Temperature is about the same throughout the lake. Ice forms on the top layer, and if it grows thick enough, it can stop light coming through and halt photosynthesis.
Spring- The ice melts, and the lake mixes again. Rising temperatures then cause the lake to begin separating again.
Water Quality
pH- 6-8 pH is the natural range for a freshwater ecosystem.
O2- Oxygen content of water depends on temperature, altitude, and pressure. The average oxygen levels for freshwater at sea level is14.6 mg/l at 0C (32F) and 8.2 mg/l at 25C (77F).
NO3- Average range in natural freshwater is 0.9-3.15 mg/L.
Chlorides (chlorine)- Freshwater has an average chloride concentration of 1-100 parts per million.
pH- 6-8 pH is the natural range for a freshwater ecosystem.
O2- Oxygen content of water depends on temperature, altitude, and pressure. The average oxygen levels for freshwater at sea level is14.6 mg/l at 0C (32F) and 8.2 mg/l at 25C (77F).
NO3- Average range in natural freshwater is 0.9-3.15 mg/L.
Chlorides (chlorine)- Freshwater has an average chloride concentration of 1-100 parts per million.