Warm-up 1. The 3 zones in a river are Identify one river zone and list 2 biological and 2 physical characteristics. 3. Identify one river zone and one species of fish that survives best in that zone. Explain why that species is adapted to that zone.
LAKES and PONDS
Formation of Lakes – Great Lakes The Great Lakes did not exist in preglacial times but are the cumulative result of several phases of glaciation that took place during the last 1.5 million years. Ice-marginal lakes (or proglacial lakes) form when the land in front of the ice slopes toward the ice, allowing meltwater to pond directly in contact with the ice, as shown below
Drainage continued southward to the Gulf of Mexico. The present-day Great Lakes formed as the earth’s crust, depressed from the weight of the ice sheets, rebounded after deglaciation.
Formation of Lakes - Volcanoes Crater Lake (Oregon) was formed after the collapse of an ancient volcano, named Mount Mazama. This volcano violently erupted approximately 7700 years ago. That eruption was 42 times as powerful as the 1980 eruption of Mount St. Helens.
Lentic Ecosystems Lakes differ from ponds on the depth and amount of water. Plants and animals are distributed within ponds and lakes according to depth of water and distance from shore. Usually ponds will have sunlight reaching the bottom all the way across the entire body of water.
ZONES of Lakes Littoral zone- a shallow well lighted area with warm water that is close to shore and hosts emergent plants. This area is the most diverse with algae, snails, insects, fish, amphibians, reptiles and mammals.
Fig. 8-15, p. 175 Sunlight Painted turtle Blue-winged teal Green frog Muskrat Pond snail Littoral zone Plankton Limnetic zone Profundal zone Diving beetle Benthic zone Northern pike Yellow perch Bloodworms
Limnetic Zone Well lighted area with open surface of water farthest from the shore. Also known as the epilimnion. Occupied by plankton, fish and some reptiles. Fig. 8-15, p. 175 Littoral zone Plankton Limnetic zone Profundal zone Benthic zone Northern pike Yellow perch
Profundal zone Also known as the hypolimnion. Deep aphotic region. ◦ Aphotic- no light penetration. Fig. 8-15, p. 175 Littoral zone Plankton Limnetic zone Profundal zone Benthic zone Northern pike Yellow perch Bloodworms
Benthic Zone Bottom of aquatic ecosystems. Nutrients are delivered to this area in the form of detritus. Detritus is the dead organic matter that “rains” down from upper areas. Has many decomposers and also fish, clams, mussels, etc.
Lake and Pond Succession OLIGOTROPHIC - are generally clear, having a low concentration of plant life. Typically glacial lakes MESOTROPHIC - have good clarity and an average level of nutrients. EUTROPHIC - are enriched with nutrients, resulting in good plant growth and possible algal blooms. Older ponds. Eutrophication - the speeding up of pond succession due to fertilizer runoff from agriculture.