Accumulation rate
(
g/m
2
/
yr)
Diatom silica
100
90
80
70
60
50
40
30
20
10
0
c. 1830 A.D.
c. 1940 A.D.
Diatom silica
Clay content
Land use shifts increasingly from
sparse dwellings/farming to residential,
which increases erosion/terrigenous
(
clays) delivery.
Increased nutrient delivery encourages
increased algal growth.
From 1830 to 1945, land use around the lake changes
dramatically, from prairie to livestock/agriculture to
denser settlement/homebuilding.
Land-use patterns set—
suburban environment—
reduced erosion.
Septic systems reduce
nutrient loading.
60
40
20
0
70
50
30
10
The white band in the sediment
(
this core is from Lake Louise) is
ash from the explosion 7,700 years
ago of Mount Mazama, which became
Crater Lake in Oregon.
The lakes Professor Tepper’s students are
studying are in close proximity yet quite
different in overall health.
29
spring
2013
arches
Waughop Lake
Lake Louise
Gravelly Lake
American Lake
Lake
Steilacoom
1
mi.
1
km