20 likes | 88 Views
Lecture 14 THE BIOSPHERE. Temperate lakes. Spring overturn: warming & winds cause oxygen to be carried downward & nutrients to be carried to the surface. During midsummer: thermocline forms between upper layers & lower cooler layers.
E N D
Temperate lakes • Spring overturn: • warming & winds cause oxygen to be carried downward & nutrients to be carried to the surface. • During midsummer: • thermocline forms between upper layers & lower cooler layers. • Thermocline prevents vertical mixing between the warmer, oxygen-rich surface layer and the cold, oxygen-poor layer below it. • During fall overturn- thermocline sinks; water mixes vertically; dissolved oxygen moves down & nutrients move up.