. Bulletin. Natural history; Natural history. September 1985 125 Years of Biological Research 249 LAKE TAHOE BASIN POPULATION GROWTH. Fig. 3. - Population gi-owth in the Lake Tahoe basin from about 1950 through 1977. The population has been divided into winter, summer, and permanent residents. The sum of both sea- sonal and year-round residents is presented as total residents. deterioration of Lake Tahoe, like that of many of the world's lakes, has accel- erated. This paper continues the docu- mentation of the changing lake and attempts to isolate some of the major factors involved. Through a
. Bulletin. Natural history; Natural history. September 1985 125 Years of Biological Research 249 LAKE TAHOE BASIN POPULATION GROWTH. Fig. 3. - Population gi-owth in the Lake Tahoe basin from about 1950 through 1977. The population has been divided into winter, summer, and permanent residents. The sum of both sea- sonal and year-round residents is presented as total residents. deterioration of Lake Tahoe, like that of many of the world's lakes, has accel- erated. This paper continues the docu- mentation of the changing lake and attempts to isolate some of the major factors involved. Through a better understanding of whole-system re- sponse, it should be possible to make more intelligent management deci- sions and eventually stabilize the fer- tility of lakes at some acceptable level. EUTROPHICATION OF LAKES Naumann (1919) used the concept of trophic status to distinguish between the oligotrophic mountain lakes and the more productive eutrophic lakes of the lowlands. Many of the world's lakes, like Tahoe, have experienced a steady increase in fertility as their watersheds have been developed for agriculture, silviculture, or urban communities. Documentation of the change has often included a variety of chemical mea- sures of fertility, such as nitrogen and phosphorus concentrations, changes in the species composition and abundance of algae, and decreases in hypolimnetic oxygen concentration during stratifica- tion. Observations of oxygen depletion under winter ice cover or following algal blooms were first made possible by the well-known Winkler technique for measuring dissolved oxygen. The measurement of primary productivity has provided a highly sensitive integra- tion of chemical, physical, and biolog- ical conditions in lakes (Goldman 1963; Goldman & Wetzel 1963). Comparison of the contrasting vertical profiles of in situ measures of primary productivity from lakes of different trophic status has previously been presented (Gold- man 1968). These profiles show
Size: 1821px × 1372px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
