Figure 8C. Crater Lake Dissolved Organic Carbon (DOC) versus depth, 1999. DOC calculated by difference (TOC-POC). Because no replicate samples were collected and analytical replicates for TOC were noisy, only the values above 200 m are plotted. DOC concentration appears to peak near 80 m, and to increase in the photic zone from July through September, consistent with a summer increase in CDOM observed in 2001 by Boss et al. (this issue).

Figure 9A. Crater Lake cp660 versus depth for 1995. Unusually high values near surface and deep in the water column are probably suspended mineral particles from storm runoff. The broad peak centered at 70 m is normal (assumed to be microbial biomass). Rain record at Crater Lake NPS Headquarters: 4–19 June = 4.7”, 6–12July = 3.8”, 25July = 0.9”. Snow pack also melted late this year (5 July 1995).

Figure 9B. Crater Lake turbidity (cp660) reached unusual levels during summer 1995 compared to 1994 (a typical year), coincident with high precipitation and runoff during Spring and Summer 1995 (see caption for Figure 10A). Both the surface and deep water (averages for 0–20 m and 300 m plotted) were elevated in early July and went much higher at the surface during the days after the 25 July thunderstorm and appears to have reached the bottom 2–4 weeks after the storm.

Figure 10A. Crater Lake rain (inches per month at Crater Lake NPS Headquarters) and chlorophyll-a (0.45 um filter), averaged 0–30 m and 40–140 m (1984–2002 July–August).