Figure 11B. Crater Lake phytoplankton photoacclimation index for 2001 (from ratio of biooptical signals, Fchl:cp660).
Figure 12A. Crater Lake particulate absorption (ap) spectra from 5 depths (20 August 2001). QFT method as modified by Lohrenz (2000) using GF/F filters (0.5–1.0 liters filtered); filter supported on quartz disc and scanned using a Shimadzu 160-UV spectrophotometer. Chlorophyll-a absorption peaks at 675 nm and 430 nm; apparent micosporine-like amino acid (MAA) peak at 325 nm (arrow) clearly visible in 25 m and 50 m samples. Chlorophyll-a concentrations calculated from 675 nm peaks (0.038–0.38 mg m-3 using ap*675=0.040) closely match the [Chlorophyll-a] calculated from data in Figure 3 using the diffuse attenuation model of Morel and Maritorena 2001. Typical ap*675 = 0.035 according to Sathyendranath et al. (1987).
Figure 12B. Absorption ratios consistent with photo protection from UV-B in phytoplankton near the surface (MAA peak versus Chlorophyll-a red peak ratio follows attenuation trend for UV-B irradiance; Chlorophyll-a blue peak versus Chlorophyll-a red peak ratio remains constant with depth). Ratio of Fchl:cp660 shows photoacclimation as in Figure 11B.
Figure 13A. Crater Lake surface Chlorophyll-a (0–30 m average and 40–140 m average, retained on 0.45 micron filter) for July and August 1984–2002, and stratospheric ozone over Crater Lake during July and August (average of day 1–17 each month for latitude +43, longitude -122, source Nimbus-7 TOMS sensor, 1978–93, Earth Probe TOMS sensor, 1993–present, http://toms.gsfc.nasa.gov/teacher/ozone_overhead_archive_V8.html).
Figure 13B. Chlorophyll-a (1984–2002 averages for July & August, 0–30 m and 40–140 m retained on 0.45 micron filter) versus Stratospheric ozone (DU) averaged for first 17 days of the sample month (see Figure 13A for source). Regression equation for deep [Chlorophyll-a], y = 0.025x – 7.45 (r2 = 0.49); for shallow [Chlorophyll-a], y = 0.0037x – 1.07 (r2 = 0.27).
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