Instantaneous amounts of organic carbon, both particulate and dissolved, in a number of freshwaters ranging from unproductive tarns to moderately productive reservoirs were measured by acid-persulfate digestion and infrared absorption. Organic carbon was designated as net seston carbon, filter seston carbon, or dissolved carbon based on filtering techniques. Repeated sampling showed amounts of organic carbon, either dissolved or particulate, fluctuated considerably over short periods of time; the dissolved fraction probably varying less than particulate forms. Almost daily measurements in samples incubated over three week periods also revealed erratic changes, with no clear reduction in total organic carbon. The data have descriptive value, although they cannot, at this time, be related satisfactorily to the general limnological knowledge.

The Southern California coastal sewage outfalls were investigated in relation to their effect upon standing stocks of phytoplankton, and on primary production. Kinetic parameters for the assimilation of ammonium, nitrate, and urea were determined at the outfall sites using N-15 labeled substrates. Laboratory studies investigated the utilization of various forms of nitrogen by phytoplankton, mechanisms and rates of nitrogen assimilation, and enzymes of nitrogen assimilation. It was found that the maximum growth rate was a variable, while the saturation constant was uniform over a range of dilution rates of N-limited chemostat cultures. The chemical composition of phytoplankton varied with dilution rate in reproducible ways. By varying the dilution rate of such cultures one seems to regulate the degree of nitrogen-deficiency of the phytoplankton.

Effects of rainfall runoff from a beef cattle feedlot on the water quality of a small impoundment were determined. Changes in chemical concentration of impounded water and changes in the community structure of aquatic organisms were measured and related to the amount and composition of feedlot runoff received. Water quality changes were also monitored in a nearby reservoir which received no feedlot runoff to serve as a control. Changes in chemical concentration or population structure of organisms were not apparent for discharges of about one-part feedlot runoff to 40 parts receiving water. Runoff discharges for two pumping periods with each contributing one-fourth of the volume of the receiving water were shown to degrade water quality in the impoundment. Several significant chemical and biological changes occurred. The most dramatic reduction in the biological community was the suffocation of about 90% of the game fish in the impoundment.

The energy budget approach to cooling ponds has been outlined and applied to cooling ponds. Monthly average weather data from 88 stations throughout the U.S. were used to calculate equilibrium temperatures, heat exchange coefficients, and amount of cooling in various sized ponds receiving the effluent from a standard power plant of 1000-mw capacity, both for average and extreme weater conditions. The data for each station is shown on a chart, and the variation of these results across the U S. is depicted by a series of 28 maps of the U.S. with contours connecting equal values of the parameters. The results may also be used to estimate cooling pond performance for other sized power plants. The maps disclose variations across the U.S., on a given date, of up to 55°F in equilibrium temperature, up to 100% difference in heat exchange coefficients, up to 50% difference in heat lost from a given sized pond, and up to 200% difference in the size of a pond necessary to produce an equal cooling effect.