Zooplankton samples (ca. 50 mL) were preserved in the field with a 10%/vol. formalin solution to a 4% final concentration in the sample. In the laboratory, all samples were stained with Eosin Y prior to processing to facilitate counting. The samples were diluted to acceptable concentrations using a Folsom Plankton Splitter. One collecting tray, from the splitter, was designated as the counting (C) tray, the other as the picked (P) tray. The sample was placed in the splitter and rocked 5x to randomize sample, then poured into the trays. The splitter was rinsed with 0.22 gm filtered Crater Lake water, rocked 5 more times and poured into the trays. The C tray was poured back into the splitter and the procedure repeated until an approximate density of zooplankton were obtained to facilitate counting (ca. 250-350 organisms/sample), by observing the tray under a stereo microscope. All other remaining organisms were retained in the P tray. Both tray samples were then filtered through 0.10 gum nitex cloth to reduce volume and remove sugar formalin, then rinsed into 25 mL liquid scintillation vials. The P vial was preserved with 1 mL of 10% sugar formalin, used for identification of zooplankton and archived. The C vial was rinsed into a Hydro-bios Kiel 50 mL settling chamber, allowed to settle undisturbed for 24 hours and the sample counted at 4x (for crustacean zooplankton) and 20x (for rotifers) with phase contrast on a Nikon Diaphot-TMD inverted microscope fitted with a Javelin color camera and Sony color printer and monitor. A digital photomicrograph was also taken of the major zooplankton taxon encountered and are included with this report. The counts were used to estimate the number of organisms per cubic meter (organisms/m 3) of lake water filtered:
N = (ndf) / VL,
where N = number of organisms per cubic meter;
n = number of organisms counted;
df= dilution factor of sample (splits);
VL= volume of (m 3 ) of lake water filtered.
Here, VL= net opening area (m 2 ) X length of tow (m) X filter factor (a 100% factor was used).
Sample Analysis
The data were recorded on computer coding sheets according to a standard format required by the programs selected for data analysis (AID 1 and AIDN). Each data file was organized into a series of blocks, each of which represented the counts of species occurring in a particular sample (i.e. ponds), the phytoplankton were not analyzed because there were only 3 samples taken. The general approach to the quantitative analysis of distributional patterns in the zooplankton involved: 1) estimation of community composition parameters (AID 1 program); 2) calculations of similarity measure for comparing the species compositions of sample pairs (AIDN program); and 3) calculations of a similarity measure for comparing the species compositions of pooled sample pairs (AIDN program).
Two indices of species diversity, the information measure and Simpson’s index were used to express community structure, H” and SDI respectively. A measure of dominance (R) for selected taxa was included. A similarity measure (SIMI [a,b]) was used to compare taxonomic similarity between samples a and b. For completeness all statistical outputs are contained in this report (Appendix 3-8).
2.3 Floral Survey
A single survey of the White Horse Bluffs and associated ponds was conducted by David J. Hartesveldt on August 21, 1993. The focus of the survey was the ponds themselves. Most of the twelve ponds were visited and all vascular plants observed in them were noted to species or were collected for later identification. A meander survey was conducted throughout the area of White Horse Bluffs and all vascular plants observed were noted to species. Unknown taxa were keyed to species within two weeks of collection.
Standard floras used to key these species included A California Flora and Supplement(Munz 1968), Flora of the Pacific Northwest (Hitchcock and Cronquist 1973), and The Jepson Manual (Hickman 1993). The names used to refer to a given taxon vary considerably from flora to flora. The names used in the Jepson Manual have been used for the purposes of this study.
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