1. An undisturbed sediment core containing varves from the deposition zone of a deep lake The varves can be used to calculate dates along the core profile

2. Paleolimnology--Pollen stratigraphy in lake sediment cores

3. Cores can be dated with radioisotopes 137 Cs (half-life 30 yr) is found in fallout from bomb tests The most commonly used isotope is 210Pb, half-life 22 yr

5. 210 Pb 218 Po 222 Rn 226 Ra 238 U The Uranium 238 decay series

7. The littoral zone, what determines its outer boundary?

8. The transparency of lake water is measured by its extinction coeficient The extinction coefficient k increases with: the concentration of organic matter (colour) of the water the amount of suspended matter eg, phytoplankton, fine suspended particles, eg clay

9. Light extinction --Light enters from above and its intensity (I) is sharply attenuated with depth (z)—absorption by water or solute molecules or scattered by particles IzIz z Photic zone z 50% z 1% z 10% Section 10.6 Page 144 in text

10. In general Photosynthesis exceeds respiration above the 1% light level and rooted plants can grow down to about the 10% light level IzIz z Photic zone z 50% z 1% z 10% Page 144 in text