Environmental Engineering Reference
In-Depth Information
Conductivity (S/m)
02468 0
2
Temperature (
0
C)
0
5
10
15
20
0
A
10
Temp.
Cond.
20
30
40
50
60
70
Chlorophyll (fluoresence units)
0.03
0.05
0.07
0.09
0.11
0.13
0
B
10
20
30
40
50
60
70
FIGURE 15.5
Vertical profiles of temperature and conductivity (A) and phytoplankton
(B) (chlorophyll fluorescence) from Lake Vanda, Antarctica [reproduced with permission from
(A) Spigel and Priscu (1998) and (B) Howard-Williams
et al.
(1998)].
A unique community is associated with liquid inclusion in the ice lay-
ers on the surface of the dry-valley lakes (Priscu
et al.,
1998). Particles from
the terrestrial habitat blow onto the ice surface. The particles absorb heat
in the summer and melt down into the ice cover. The liquid water sur-
rounding the particles supports a community of algae and bacteria.
Streams feed the dry-valley Antarctic lakes. These streams flow only
during a few months of the year when the sun is warm enough to melt the
glaciers. The channels dry frequently and generally are frozen when they
are dry. Amazingly, the channels have significant biomass of algal primary
producers, mostly cyanobacteria. These organisms can be freeze-dried for
much of the year, but they are able to actively photosynthesize minutes af-
ter being wetted (Vincent, 1988).
Arctic lakes and ponds are also generally very cold. Ponds and lakes
can freeze to the bottom; if they freeze completely, they will not contain
fish or many macrophytes. Many fish can withstand and compete well at
temperatures down to 0°C; however, most species have optimum growth
above 8°C (Elliott, 1981). Aquatic mosses are often the only macrophytes
found in Arctic lakes. The mosses grow slowly and are 7 to 10 years old.
This is a greater longevity than has been documented previously for any
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