Project at a Glance
Title: Chemical and biological characteristics of Emerald Lake and the streams in its watershed, and the responses of the lake and streams to acidic depositions
Principal Investigator / Author(s): Melack, John M
Contractor: Marine Science Institute and Department of Biological Sciences, UC Santa Barbara
Contract Number: A6-184-32
Research Program Area: Ecosystem & Multimedia Effects
Topic Areas: Acid Deposition, Ecosystem Impacts
The hydrochemistry and aquatic ecology of Emerald Lake (a small, high-altitude lake in the Sierra Nevada, California) and the streams in its watershed have been studied for 5 years (1983-88), with an emphasis on the effects of acidic deposition. Time-series data collected throughout the year are presented for major ions, nutrients, trace metals, chlorophyll, zooplankton, and zoobenthos, and the seasonal and interannual variations in these variables are analyzed. Benthic chambers were used to measure the flux of solutes from sediments and rock surfaces to overlying water. Mass balances were calculated for major solutes in the lake. The hydrochemistry of inflow streams was measured over the course of several spates resulting from storm runoff. A numerical model of phytoplankton production was formulated from productivity measurements and other data. The ecology and population dynamics of the brook trout (Salvelinus fontinalis) were studied in detail, and the distribution of tadpoles of the Pacific treefrog, Hyla regilla, in ponds was surveyed for several years. Experimental acidification of large enclosures in the lake was conducted to determine the responses of the phytoplankton, zooplankton, and zoobenthos. Surveys of nearby lakes showed that Emerald Lake is representative of Sierran lakes with trout.
The overall conclusion of this research is that Emerald Lake is not currently showing serious chemical or biological effects of acidification. Many aquatic animals known to be acid-sensitive are found in the lake and streams, and the trout population does not show signs of acid-induced stress. However, the lake and streams are extraordinarily sensitive to acidification because of their extremely dilute ionic chemistry. Generation of acid neutralizing capacity (ANC) by processes within the lake is insignificant relative to ANC generation by watershed processes. Our experimental work indicates that even slight acidification of the lake will result in changes in the species composition of the zooplankton assemblage. Episodic acidification, particularly during snowmelt, could have direct deleterious effects on sensitive early stages of trout. If acidic deposition were to increase, the lake and streams would be readily affected.
For questions regarding research reports, contact: Heather Choi at (916) 322-3893
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