Influence of Sediment Inflow on Phytoplankton Primary Productivity in Lake Tahoe (California-Nevada)

✍ Scribed by Dr. Max M. Tilzer; Dr. Charles R. Goldma; Robert C. Richards; Robert C. Wrigley

• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: English
• Weight: 950 KB
• Volume: 61
• Category: Article
• ISSN: 1434-2944
• DOI: 10.1002/iroh.19760610204

✦ Synopsis

Abstract

Light, nutrient concentrations and phytoplankton photosynthesis were studied in a Lake Tahoe sediment plume during maximum spring runoff. They were compared with conditions in clear lake waters not influenced by inlets. In the plume, nutrient concentrations increased in proportion to sediment density whereas light transmission of water was reduced with little effect on the spectral composition except for red light. Light inhibition of photosynthesis at the lake surface was less pronounced in the plume than in clear water and light limitation occurred more rapidly in deeper layers. Evidence from both lake experiments and laboratory bioassays suggests that iron had the greatest stimulatory effect on both photosynthetic activity and biomass growth at maximum sediment densities near the stream inlet.

Because of less surface inhibition, photosynthetic light energy utilization efficiency was usually higher in the sediment plume which occurred in relatively shallow areas near the shore. In order to estimate overall effects of enhanced turbidity associated with nutrient loading on Lake Tahoe's primary productivity, profiles taken in shallow areas near the lakeshore were extrapolated to the maximum depth of photosynthesis. Light limitation would cause decreasing productivity, but nutrient stimulation would make this effect less pronounced. The overall effect would depend on the extent of sediment loading relative to nutrient loading.