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FIGURE 4.5 Fractal values for aggregates sampled and analyzed on filters over three years, comprising four different bio-physical open water conditions. Dark bars represent ambient suspended sediment conditions while lighter colored bars are resuspended, gravel stored fine sediments. Error bars represent the 95% confidence intervals.

I Total population Floc ESS8 Compact

I Compact organic

|_Aug 10 2000_ Ambient

|_Aug 10 2000_ Resuspended

Ambient

Resuspended

Fish die-off

Post-fish presence

Active spawn Springmelt floods -.- ^

30/ 5/ 97-1/ 6/97 10/8/00 26/8/96 21/9/00 Sampling date

5/10/00

indicating that the particles are more rounded. In contrast to the results of the settling particle fractal analysis (Figure 4.4) the D values for filtered suspended sediment increase later in the season, becoming significantly less rounded during fish die-off and in post-fish periods (Figure 4.5). In the active spawn sampled in August 2000, the suspended and gravel stored fractals are not significantly different from each other. These low D values represent more rounded particles and are similar statistically to the suspended sediment of the spring melt flood and the gravel stored samples throughout the full sampling season.

In 2001, gravel stored fine sediments collected from infiltration bags were introduced into the settling chamber and analyzed for size, shape (fractal), and settling characteristics (density). Table 4.4 shows these data along with the cumulative number of spawning fish returned to O'Ne-eil Creek by that date. Particle diameters were largest pre-fish and post-fish with the smallest mean values occurring at mid-spawn. Particle densities increased chronologically until die-off when they significantly decreased. Density increases were significant again in the post-fish sediments. The temporal pattern is that pre-spawn gravel stored aggregates are large and low density, mid-spawn aggregates are small and high density while at seasons end (post-fish) the gravel stored aggregates are again large but high density. While the fractal values for all of the infiltration bag sediments are low, the smallest D values, representing the roundest particles, were noted at mid-spawn and post-fish which is also when densities were highest. Figure 4.6 shows the changing pattern of fractal values over time along with a temporal plot of the cumulative spawner numbers in 2001. This indicates the number of individual fish having passed the counting fence by that date. On August 3, when 10,931 have returned to the stream to rework the gravels for redd construction the particles are more rounded than at all times except for the period when no visual evidence of fish carcasses are apparent in the stream (post-fish).

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