Yellowstone National Park Report
There is evidence to suggest that the primary productivity of Yellowstone Lake may have decreased during the last 1500 years, with an accelerated decline in the last 100 years. Shero and Parker (1977) analyzed diatom frustules preserved in lake sediments and described a gradual decrease in both numbers and volume of frustules over the past 1500 years, although species composition has remained relatively constant. Varley (1974, and personal communication) compared chemical analyses of lake water made in 1884 with recent analyses and found lower concentrations of several elements in the recent samples. He also notes that early visitors at the Lake Hotel often complained about the offensive smell of rotting "seeweed" piled 3-4 feet deep on the beach, whereas only scattered macrophyte detritus can be found on the lake shore today.
Romme, W. H. and Knight, D. H.
"Yellowstone Lake: An Evaluation of Patterns in Productivity,"
University of Wyoming National Park Service Research Center Annual Report: Vol. 7
, Article 22.
Available at: http://repository.uwyo.edu/uwnpsrc_reports/vol7/iss1/22