Michigan Department of Conservation
Research and Development Report No. 43
Institute for Fisheries Research Report No. 1709, 1965
Use of As-74 Tagged Sodium Arsenite in a Study
of Effects of a Herbicide on Pond Ecology
Robert C. Ball, Professor
Department of Fisheries and Wildlife
Michigan State University
East Lansing, Michigan, U. S. A.
and
Frank F. Hooper, Biologist in Charge
Institute for Fisheries Research
Michigan Department of Conservation
Ann Arbor, Michigan, U. S. A.
Introduction.-In the lake districts of the United States aquatic weed control has become commonplace and necessary. Utilization of these waters for a variety of recreational purposes has created a demand for the elimination of nuisances associated with an overabundance of weeds.
A variety of chemicals are available for the control of higher aquatic plants and algae but sodium arsenite and copper sulfate are still widely used. These two herbicides have remained popular for over 50 years [6] despite the discovery of newer organic herbicides. Their lasting popularity can be attributed to low cost and general effectiveness. It has been assumed that they have little effect upon the aquatic biota.
Despite the fact that sodium arsenite has been used for many years, little is known about its effect upon aquatic ecosystems or the ultimate fate of the chemical within the lake or pond. Also important but poorly understood is the long-term effect of prolonged treatment. Dupree [2] studied the arsenic content of various components of a pond ecosystem following treatment with arsenite. He found that a considerable amount of arsenic was retained by the muds. This was slowly released to the water when the ponds were drained and refilled. He found that plankton concentrated the herbicide and noted concentration as high as 7200 ppm within plankton organisms.
Lawrence [4] found that sodium arsenite markedly reduced fish production in treated ponds and killed most of the microcrustaceans and rotifers. Riggs [5] investigated the effects of several herbicides on a series of aquatic plants and described the possible ways in which sodium arsenite might attack plants.
Attempts to trace sodium arsenite through an aquatic ecosystem have been hindered by the lack of good technique for analysis of arsenic. Conventional methods are inefficient and time consuming. In this study we utilized sodium arsenite labeled with radioactive arsenic (As-74) to trace the movement of arsenic through aquatic ecosystems following their treatment with herbicide. The overall investigation was divided into three phases. The first was a study of the movement of sodium arsenite through the ecosystem of a small pond. The second was an approximate duplication of the pond study but was carried out by means of a series of aquaria experiments in which conditions were carefully controlled. The third phase was a study of the effect of sodium arsenite upon the metabolism of a pond. The latter phase did not utilize the tracer (As-74). This report will deal mainly with the latter of the two phases although limited data are presented from the pond study.
We wish to acknowledge the assistance of Mr. Thomas Bahr, Mr. Leonard Sohacki and Mr. Jack Bails who collected data used in certain phases of this study. Research was carried out under AEC contract AT (11-1) 655. A portion of the work was done under Dingell-Johnson Project F-27-R, Michigan.