FIELD CHEMICAL EXAMINATION OF THE WATERS IN TENNESSEE STREAMS CHARLES S. SHOUP Department of Biology, Vanderbilt University Nashville, Tennessee Reprinted from the JOURNAL OE THE TENNESSEE ACADEMY OE SCIENCE, Volume XXV, Number 1, January, 1950. FIELD CHEMICAL EXAMINATION OF THE WATERS IN TENNESSEE STREAMS' CHARLES S. SHOUP Department of Biology, Vanderbilt University, Nashville, Tennessee INTRODUCTION Fresh-water biology is a relatively new field of investigation in the southern United States, particularly in connection with fisheries re- sources and potential fish production. In the country as a whole such studies began only a little more than a half-century ago, and date from pioneer work on the Great Lakes and the important examina- tions made of the Illinois River system by S. A. Forbes (1877, 1893, 1911, 1928) with varied studies in other regions. The work of E. A. Birge and Chancy J uday (1904, 1907, 1910, 1914) on Wisconsin lakes beginning almost with the new century and of J. E. Reighard (1894) in Michigan and of C. A. Kofoid (1903) in Illinois initiated recognition of the importance of knowledge regarding biological bal- ance in fresh waters, the maintenance of which pays dividends in fishable streams and sometimes in marketable fish flesh. These studies of the general water chemistry from Tennessee streams were begun in 1938 as a part of the biological survey work which was at that time being conducted by the Tennessee Department of Conservation, Division of Game and Fish, and which ended as a state-supported enterprise in the summer of 1941. Since the war the additional supplemental and confirmatory information contained in this report has been obtained by the author, and is now offered as a contribution to support the previously-published papers which have resulted from the efforts of the first biological survey in Tennessee (Shoup, 1940; Shoup and Peyton, 1940; Shoup, Peyton, and Gen- try, 1941 ; Gentry, 1941 ; Hobbs and Shoup, 1942; Shoup, 1943; Wright and Shoup, 1945; Shoup, 1947). The remarks in this introduction are intended to be of an inform- ative nature with respect to interpretation of the tabulated results, and are intended to be general enough to serve as a guide for individuals who may begin field water chemistry studies in relation to other biological problems. The environment of fresh-water organisms is a complex of many continuously-operating processes and unstable conditions. The physical factors are determined by materials held in suspension or in 'The author wishes to acknowledge with thanks a summer grant-in-aid for completion of this work, awarded from the Carnegie Foundation Research Fund allotted to the Graduate Faculty of Vanderbilt University, and a small grant towards extra printing costs from the Natural Science Research Fund of Van- derbilt University. —4- Chemical Examination of Tennessee Waters 5 solution in the water and by the water temperature, depth, movement, illumination, shoreline, and bottom. Chemical factors which are in- fluential upon both plant and animal life in a stream, and which must be recognized, are found in the acidity or alkalinity of the waters and in the gases, salts, and the extraneous harmful or beneficial organic materials contributed to the stream from the environment. The organisms themselves which live in water make up a biological en- vironment, and living or dead, as food, as feeders, as parasites or hosts, are a portion of the environmental complex. The problem of the fisheries biologist would be to determine as best he could the optimum favorable conditions of the aquatic environment. His prob- lem is to learn something of the beneficial relations of these con- stituents, both living and non-living. On becoming acquainted with these factors in any local situation, the fisheries biologist is aided enormously in his setting up of a system of fish management which could become essentially a method of environmental control. Provid- ing extraneous factors are favorable, this environmental control should, ideally, result in higher water fertility, more food organisms, a greater production of food or game fish in a stream, and the elaboration of concepts which could result in a sound stocking policy for a region. Chemically pure water does not exist in or upon the earth, and most natural waters show considerable differences in their chemical content as solvents. It is quite likely that the exposed waters with but apparent minimal solutes are nevertheless rather complex. A lake or stream receives from the atmosphere and from its drainage area many materials which occur in the waters as dissolved or sus- pended matter. Water itself dissolves more substances than any other liquid, it combines chemically with quite diverse compounds, and shows a marked ability to gain or lose gases with great rapidity. For these reasons the chemical examination of water is an essential part of the fisheries survey and an integral part of any program directed toward fisheries management and improvement. DISSOLVED OXYGEN REQUIREMENTS Most all organisms living in fresh waters, with the exception of anaerobic bacteria in bottom deposits or perhaps certain parasites, demand a suitably-maintained supply of free oxygen for a continued existence. Most game fishes seem to prefer water with at least three or four parts per million of dissolved oxygen (Needham, 1938). This means that it becomes necessary to establish where in a lake, providing oxygen deficiences are known to exist, the four parts per million line of oxygen concentration is located. This also means that determination of oxygen concentration should be made from time to time in streams in order to detect pollution or oxidation processes which cause a drop in oxygen concentration. Generally, in an un- polluted stream, there is no problem as to the oxygen and carbon dioxide content of the water. Flowing water, moving alternately 6 Report of the Reelfoot Lake Biological Station through pools and riffles, is usually maintained saturated with oxygen in equilibrium with any given temperature, and is sufficiently areated to free it of unusually large amounts of carbon dioxide, the concen- tration of the latter being equilibrated for any given temperature with the carbon dioxide of the atmosphere. This concentration of carbon dioxide in the atmosphere (0.03 percent) is not likely of detectable influence upon respiration or respiratory movements of aquatic or- ganisms, but a rise in carbon dioxide concentration to fairly high values may accelerate these processes in aquatic organisms as shown by Botjes (1932) in Coriza at six percent CO2, and by Dontcheff and Kayser (1936), who demonstrated that the European frog Rana viridis increased its oxygen consumption 20 percent at 10°C. and 10 percent at 20°C. when exposed to air in which the amount of carbon dioxide had been raised to 1.0 percent of an atmosphere. In a lake, only the surface waters are exposed to the atmosphere, and by mix- ing, have some chance to liberate carbon dioxide and take on a new supply of oxygen through solution. In most lakes, especially in our southern regions, this surface water is too warm on hot days of mid- summer, not only for rainbow trout (Needham, 1938, pp. 50-51), but perhaps in many cases for small-mouth bass as well (Kuhne, 1939, p. 96). On such occasions, in order to survive, game fishes must retreat into the cooler deeper waters or into bottom waters where, unfortunately, in many instances there is an insufficient oxygen sup- ply. Since warm waters are incapable of carrying as much oxygen as cool waters (Theroux, Eldridge, and Mallmann, 1936, Table 9, p. 186), our southern warm-water streams also may have at times a somewhat low oxygen concentration in exposed deep pools during the height of a hot season. This means that such conditions should be checked to see if they may exist before stocking is attempted in any lake or stream. CARBON DIOXIDE There appears to be but little accurate information on the true and exact toxic action of carbon dioxide upon aquatic organisms living in our fresh waters, but Powers (1934, 1937) is of the opinion that sudden changes in the concentration of carbon dioxide in water or the migration of fishes into alternate high or low or low and high CO.-tension regions will be markedly detrimental to them. We know, of course, that normally the waters of streams carry but very low levels of carbon dioxide tension as free CO2 approximately in equilibrium with that of the atmosphere at about 0.23 mm. Hg. partial pressure. Abnormal conditions can be imagined which would cause the saturation of waters with carbon dioxide due to its great solubility. In such an event, carbonic acid in great quantities could be formed, and in these rare cases, considering the ease of permea- bility of carbonic acid to cells and tissues, toxic action on aquatic organisms would be immediately manifest. When a rapid reduction in concentration of carbon dioxide occurs in an atmosphere above the water, there would be a correspondingly marked fall in the car- Chemical Examination of Tennessee Waters 7 bonic acid level in the water. Carbon dioxide normally liberated in natural waters comes from plant and animal metabolic processes which are essentially oxidations which eventually also involve an uptake of oxygen, from the decay and oxidation of vegetation in the bottoms of lakes and streams, and from slow oxidative processes oc- curring in bottom muds and caused by large numbers of certain bacteria. Under ordinary conditions, as stated above, the water flow and turbulence at rapids and riffles is sufficient for elimination of excess carbon dioxide. Occasionally, in deep pools and in very long reaches of slow flow in streams, and in deep lakes, the carbon dioxide content of the waters may rise to physiologically-active levels, gen- erally in association with a lowered oxygen tension.