PE EIE[R-Rg RESEARCH ON - HJ Andrews Experimental Forest

measurements of algal response and the tw o
most commonly limiting nutrients probably
represent a minimum list of variables most
pertinent to the eutrophication process . To
increase the general value of such guidelines ,
the data base should be more extensive in
addition to including sediment constituents .
Cedar River Drainage Lakes
Comparison of nutrient and plankton characteristics
in the four lakes of the study are a
(table 2) shows that Lake Sammamish is inter -
mediate in trophic status. Data from May t o
August show Lake Sammamish to be slightl y
more eutrophic than Lake Washington based
on mean nutrient concentrations, but less
eutrophic based on algal density and productivity
indices. Judging trophic status fro m
nutrient content during the growing seaso n
can be misleading . Lake Washington is actually
more than twice as enriched as Lake Sammamish
based on annual P supply (0 .48 versu s
0.20 g/m2 ), which conforms to the differences
in productivity .
Of more interest in table 2 than the comparison
of Lake Sammamish and Lake Washington
is the striking contrast in the tota l
series. Findley Lake is clearly oligotrophic ,
while Lake Washington near sea level is apparently
transitional between mesotrophy an d
eutrophy . Lake Chester Morse and Lake Sammamish
are intermediate in elevation an d
trophic status, but nearly as widely separate d
as are Findley and Washington (for other
morphometric data, see Taub et al . 1972) .
Data from these four lakes alone should pro -
vide a substantial framework for prediction of
trophic status from lake nutrient supply an d
morphometry information, which is important
to lake management .
The two oligotrophic lakes are also widely
different than the mesotrophic lakes in sediment
characteristics and ionic composition .
Table 3 summarizes data on major chemical
ions for the four lakes . A graded sequence in
water chemical composition from the lakes in
the upper drainage to Lake Washington is
readily apparent. A four- to tenfold increase
in concentration is observed with most
chemical parameters when comparing Findley
and Chester Morse Lakes to Lake Sammamish
and Lake Washington . These radical differences
in chemical quality of the lake waters i n
the Cedar River Drainage are primarily due to
diversified human use and different geologic
formation of the lake basins .
Results of analyses for total C, N, and P i n
samples of surface sediments are presented in
table 4 . The larger C concentrations and the
higher C/N ratios in the sediments of Findley
and Chester Morse Lakes when compared
with those values in the lakes of lower elevation
appear to reflect trophic status and are
most probably due to differences in allochthonous
and autochthonous inputs . In th e
two oligotrophic lakes, most of the organic C
in sediments is derived from allochthonou s
sources which are relatively resistant to mineralization,
partially as a result of low N availa -
Table 3.-Average summer (1971) chemical ion content in surfac e
waters of Cedar River drainage lakes (Barnes 1972 )
Lake HCO 3 S0 4 Cl Ca Mg Na K Specific conductanc e
mg/1 micromhos/cm at 25° C
Findley 9 .8 0 .4 0 .6 1 .1 0 .3 0.8