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Alex E. Dong

Publications and source records attributed to Alex E. Dong.

6 recordsLinked to original sources
USGS1977

Phytoplankton distribution and primary productivity in Donner Lake, California

Donner Lake is an unenriched system in the Lake Tahoe basin of the Sierra Nevada of California. The lake has a surface area of 1.5 square miles (3.9 square kilometres) and a drainage area of 14 mi 2 (36 km 2 ). The maximum depth is about 200 feet (60 metres). Between May and December 1973, the phytoplankton in Donner Lake was represented by 6 classes and at least 25 genera. The dominant green alga was the desmid Cosmarium staurastroides , which comprised about 25 percent of the total phytoplankton collected. The dominant diatom was Asterionella formosa , which comprised about 13 percent of the total phytoplankton. Blue-green algae were represented by Chroococcus sp., but were never abundant and constituted only 1.5 percent of the total organisms sampled. The depth of the euphotic zone from May through September ranged from 35 to 93 feet (11 to 28 metres). Thermal stratification was strong throughout the summer with a maximum temperature difference between the surface and bottom water of 17° Celsius in July. Average phytoplankton concentrations were often greater below the euphotic zone than in the euphotic zone. This pattern of phytoplankton distribution is similar to nearby Lake Tahoe and other oligotrophic lakes. Three primary productivity measurements were made during the study using the carbon-14 method. The primary productivity values were 93, 64, and 56 milligrams of carbon per cubic metre per day for May 17, August 13, and October 16, respectively. The productivity profile in May was shallow and unimodal, whereas the August and October profiles were deeper and biomodal. Dissolved-oxygen concentrations were maximum at the same depths as maximum primary productivity. On the basis of phytoplankton types and their vertical distribution patterns, and upon primary productivity measurements, Donner Lake is considered oligotrophic.

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USGS1976

Water-quality study of a reach of the Merced River in Yosemite National Park and vicinity, California, April 1973 through September 1974

A 25-mile (40-kilometre) reach of the Merced River was studied to provide the National Park Service with water-quality data prior to the operation of a new sewage-treatment plant. Data were collected periodically at four Merced River and two inflow stations. Discharge varied seasonally with highest flow occurring at the time of spring snowmelt runoff. Lowest flow occurred during late summer, coinciding with high park visitor use and elevated water temperature. Water-quality variables investigated were discharge, temperature, major chemical constituents, selected trace metals, specific conductance, suspended sediment, turbidity, dissolved oxygen, pH, alkalinity, carbon dioxide, total organic carbon, nitrogen, phosphorus, algal growth potential, coliform bacteria, periphyton, and benthic invertebrates. Diel measurements were made at some stations to delineate daily fluctuations in selected water-quality variables. Results indicate that water in the reach of the Merced River studied was of good quality. The river had low concentrations of dissolved solids (8 to 41 milligrams per litre) and low alkalinity values (2 to 24 milligrams per litre of alkalinity as CaCO 3 ). Mean concentrations of nitrogen and phosphorus were highest in the Merced River at Rancheria Flat. Algal growth potential tests showed that phosphorus was limiting algal growth at Happy Isles Bridge, El Capitan Bridge, and South Fork Merced River, whereas nitrogen was limiting growth at Rancheria Flat. Input of excessive nitrogen and phosphorus concentrations in the Merced River during the summer low-flow period, and mixing with warm tributary inflow could cause excessive algal growth and production. The algal types found were diatoms, green algae, and blue-green algae. Biomass/chlorophyll a ratios in the Merced River were low (0.3 to 7.7). Benthic invertebrates consisted chiefly of Diptera, Ephemeroptera, and Plecoptera.

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USGS1975

Limnological data for Donner Lake, California, May 1973 through December 1973

Donner Lake is easily accessible to the metropolitan areas of Sacramento and San Francisco and is close to many recreational areas in the Sierra Nevada. The lake is used for recreation and is bordered by commercial establishments, summer vacation homes, and a large state campground. Domestic wastes around the lake have received only septic tank treatment. A sewerage system under construction and partly in use at the time of this study has been completed and now (January 1975) all domestic wastes are transported out of the basin. In September of 1969 and 1970, a brief survey of the lake was conducted (Iwatsubo and others, 1972, p. 28). The results of that study indicated a well-established thermocline between 33 and 66 ft (10 and 20 m). A subsurface maximum in the dissolved-oxygen concentration occurred between 46 and 66 ft (14 and 20 m). In the shallow littoral zone, periphyton and patches of submerged rooted plants were visible. In order to remain attractive for recreational use, Donner Lake will require sound management. A thorough understanding of the water quality in the lake and the quality of inflow and outflow is of paramount importance.

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USGS1974

Limnological study of Lake Shastina, Siskiyou County, California

Lake Shastina provides water for irrigation in Shasta Valley, as well as recreation. Presently, its shoreline is being developed for summer homes. Surface water constituted more than 90 percent of the approximately 50,000 acre-foot (62-cubic hectometre) inflow to Lake Shastina in the 1972 water year. Controlled outflow is via the Montague Main Canal; however, leakage from the lake through volcanic rocks to the northwest was estimated to be greater than the measured outflow. Appreciable annual changes in the quantity of water in storage in the lake are related mainly to variations in annual inflow. From June through August the lake was thermally stratified. In the spring and summer the epilimnion was often supersaturated with oxygen, while at the same time the hypolimnion was undersaturated and 'often devoid of dissolved oxygen. Vertical stratification of carbon dioxide, carbonate, bicarbonate, hydrogen ion, nitrogen, and phosphorus was also recorded during the spring and summer. Orthophosphate, total phosphorus, and total nitrogen concentrations (organic, ammonium, and nitrate) were highest in the hypolimnion during the period of thermal stratification. Ten-inch (25-centimetre) core samples from the reservoir bottom were chemically analyzed at 0.8-inch (2-centimetre) intervals. The concentrations ranged from 6.3 to 28.9 milligrams per gram of iron, 0.07 to 0.43 milligrams per gram of manganese, 0.4 to 2.7 milligrams per gram of organic nitrogen plus ammonium, and 0.06 to 1.3 milligrams per gram of total phosphorus. Organic matter in the cores ranged from 4 to 14 percent. Green algae and diatoms were the dominant algal types, reaching maximum concentrations of about 7 and 30 million cells per litre, respectively. These phytoplankton occurred near the surface during thermally stratified periods, but were distributed at greater depths during nonthermally stratified periods. Blue-green algae were present only in the spring samples, and reached a maximum concentration of about 5 million cells per litre. Zooplankton numbers were greatest in March, July, and September, with lesser concentrations in June. Three major zooplankton groups, Cladocera, Copepoda, and Rotifera, were present. The major groups of benthic organisms were Oligochaeta, Chironomidae, and Chaoborus, with numbers ranging from 3350, 890, and 8450 per square metre, respectively. A discussion on algal control is included.

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