Submitted by Anonymous on Sat, 08/11/2007 - 14:18
Forums
Alaska Climate Variation

ms foletta

    have you come across any signs that the lake has been thermally startified and gone though turnovers if so what did you see that clued you in on it. also have you come across any extinct plants that used to live back then but like died off if so do you think it was do to the amount of sunlight in the area or just some type of predator came and became more abundent and the plant died off. im just wondreing and i cant wait for school to start yay.

                                                  -augie lombera III-

Thu, 08/16/2007 - 12:22

Peggy Foletta

Hi Augie!  Good questions.  Yes there is evidence of thermal stratification.  We retrieved temperature sensors at each of the three major lakes we visited.  The research team put two sensors with sediment traps, one near the bottom and one near the surface.  In spring when the ice melts the water is of similar density throughout and can mix from top to bottom.  Wind causes the water to mix and brings up nutrients that have sunk to the bottom.  This allows plankton at the surface to thrive and reproduce.  With sunlight for photosynthesis and nurtirents from the bottom, phytoplankton blooms.  Check this website I found on the internet:  http://www.dnr.state.wi.us/org/water/fhp/lakes/under/mixing.htm.I don't know which plants here have come and gone.  I did notice a big difference in plants at different elevations.  I was particularly impressed with the plants from the tundra.  They are very reduced in size because any plant part exposed in the winter above the snow will be exposed to extremely cold temperatures and wind and will most like die.  So for protection the plants are very low to the ground.  
See you Monday!
Mrs. Foletta