7 research outputs found
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Relationships between inorganic nutrient input, algal density, herbivore density, and residual inorganic nutrient
The relationships between inorganic nutrient supply and the first two trophic levels have long been understood in a very approximate manner but the dynamics of such a system cannot be explored adequately by simple
arithmetic when nonlinear relationships exist. An exploration of such a
system was accomplished by the use of a mathematical model based on experimental
data from a pair of two-stage continuous cultures of the alga Chlamydomonas reinhardti and the herbivorous protozoan Tetrahymena vorax
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Nitrogen transformation
Nitrogen fixation rates were determined periodically by the acetylene
reduction technique at three depths in each of the lakes. Fixation began
in June in Lakes Washington and Sammamish and peaked during July and
August. Chester Morse and Findley Lakes did not exhibit acetylene
reduction activity until August and the rates encountered were much lower
than in the other two lakes. Nitrogen fixation in the lakes correlates
closely with the concentrations of blue-greens
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Nitrogen transformations
The feasibility and enumeration studies have led to the following conclusions: The nitrogen fixation studies should be done in 1973, using acetylene reduction technique with some verification by N15. The denitrification studies should be done with N15 technique. The decision to continue more enumeration sampling of nitrogen transforming bacteria should be based on comparisons of the 1972 enumerations with the chemical budget The pertinent literature is listed in the appendix of the report; the reprints are housed in Dr. Taub's office, 212 Fisheries Center, University of Washington. The enumeration data are presented in the report
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Benthic macroinvertebrate production
Macroinvertebrates were sampled on a regular basis from March to October
1973. A relationship between chironomid length and biomass was established.
Production equations to be used for these insects are reported. A similar
length/weight relationship is presently being explored for the oligochaetes.
A proposal is made for calculating their production as well as for sphaerids
and P. affinis. Sampling is expected to continue at least through March
1974 to give a full year's data. In the near future the results of this
study are to be correlated with studies concerning primary production,
fish feeding habits, lake sedimentation rates, and physical properties
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Estimates of biomass of detritus food chain
Macrobenthos populations of the IBP lakes were sampled during October and November of 1972. Analyses of the samples revealed dominance of chrinomids and oligochaetes in both littoral and profundal regions for at least this time of year. Due to sampling difficulties the oligochaete material was not used for chemical analyses. Biomass per square meter was determined for the chironomids. From these data, literature values were used to estimate calories, carbohydrate, fat, and protein per square meter. A model taken from Johanson and Brinkhurst (1971b) is presented as a means of determining amounts and pathways of detrital input to higher trophic levels. Because this model encompasses more than the macrobenthos, data from other concurrent IBP studies will be used. The model and the 1972 project have suggested different sampling regimes and methods to be undertaken in 1973.Best copy available