State of the Lake 2009 - Tahoe Environmental Research Center ...

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TERC.UCDAVIS.EDU CLARITY Secchi depth measurements In 2008 Secchi depth has a strong seasonal feature which was clearly expressed in 2008. The deepest Secchi depth readings (the clearest water) typically occur in winter and 2008 was no exception. In 2008, the deepest reading was 122 feet on April Meters 0 5 10 15 20 25 30 35 40 Annual average TAHOE: STATE OF THE LAKE REPORT 2009 24th, while the lowest (37 feet) was measured on August 5th. This represents an 85 foot swing in clarity this year. A Secchi depth in Lake Tahoe of 37 feet is uncommonly low and the reduced readings in July and early August could have resulted from smoke transported into the Tahoe basin from significant regional wildfires that began in late June. The annual average Secchi values (Fig. 11.1) represent the most robust indicator of the status and trend in Lake Tahoe clarity. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2008 0 20 40 60 80 100 120 Feet 11.2
Depth (feet) TERC.UCDAVIS.EDU CLARITY TAHOE: STATE OF THE LAKE REPORT 2009 Penetration of photosynthetically active radiation In 2008 Photosynthetically active radiation (PAR) is that part of solar radiation spectrum that is utilized in photosynthesis. The black line below shows the depth at which PAR is 1% of its level on the lake surface, known as the euphotic depth. PAR penetration 0 50 100 150 200 250 300 350 400 450 500 varies throughout the year, but is often deepest in the summer when the sun is highest in the sky. In 2008, the euphotic depth increased in February and March, corresponding to the onset of deep mixing when clear bottom water is brought to the surface (Fig. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 8.9). 2008 was the second year in succession when deep mixing occurred. This year, the maximum Secchi depth reading was 122 feet on April 24th, which also corresponded to the occurrence of the maximum PAR penetration. 1000 100 10 1 0.1 0.01 0.001 Photosynthetically active radiation (watts per square meter) 11.3
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TAHOE: STATE OF THE LAKE REPORT 200
Page 3 and 4:
INTRODUCTION The University of Cali
Page 5 and 6:
EXECUTIVE SUMMARY (CONTINUED FROM P
Page 7 and 8:
ABOUT LAKE TAHOE AND THE TAHOE BASI
Page 9 and 10:
MAP OF TAHOE BASIN DATA COLLECTION
Page 11 and 12: Rainbow, Brook, Brown and Lake trou
Page 13 and 14: 100% 90% 80% 70% 60% 50% 40% 30% 20
Page 15 and 16: ASIAN CLAM Asian Clam Excretion Exp
Page 17 and 18: ASIAN CLAM Asian Clam Size Distribu
Page 19 and 20: Temperature ( o F) 60 55 50 35 30 M
Page 21 and 22: Temperature ( o F) 70 60 50 40 30 2
Page 23 and 24: Inches 70 60 50 40 30 20 10 0 METEO
Page 25 and 26: Percent 80 70 60 50 40 30 20 10 0 M
Page 27 and 28: PHYSICAL PROPERTIES TERC.UCDAVIS.ED
Page 29 and 30: Feet 6232 6230 6228 6226 6224 6222
Page 31 and 32: Temperature ( o F) TERC.UCDAVIS.EDU
Page 33 and 34: Temperature ( o F) TERC.UCDAVIS.EDU
Page 35 and 36: Density Difference (kilograms per c
Page 37 and 38: Mean daily streamflow (cubic feet p
Page 39 and 40: NUTRIENTS AND PARTICLES TERC.UCDAVI
Page 41 and 42: TERC.UCDAVIS.EDU NUTRIENTS AND PART
Page 43 and 44: Metric Tons TERC.UCDAVIS.EDU 10 8 6
Page 45 and 46: Dissolved inorganic nitrogen (micro
Page 47 and 48: Nitrate−nitrogen (micrograms per
Page 49 and 50: BIOLOGY 10
Page 51 and 52: BIOLOGY Algae abundance Yearly sinc
Page 53 and 54: BIOLOGY Depth of chlorophyll maximu
Page 55 and 56: BIOLOGY TAHOE: STATE OF THE LAKE RE
Page 57 and 58: BIOLOGY Nutrient limitation of alga
Page 59 and 60: BIOLOGY Shoreline algae distributio
Page 61: TERC.UCDAVIS.EDU CLARITY Annual ave
Page 65: TERC.UCDAVIS.EDU OUTREACH AND EDUCA
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