In the Brasstown Bald stream in 1959, 

 reductions in numbers of bottom invertebrates 

 were significant in the treated area, as seen 

 in table 6, but were not serious in the control 

 section (table 7). Stoneflies, mayflies and 

 dipterans were affected in the treated stream; 

 some of them recovered moderately well after 

 4 months. Reduction in the control stream was 

 mainly among midges, stoneflies and mayflies; 

 recovery in these groups after 4 months was 

 satisfactory within the limits of accuracy of the 

 collection methods. Station 3 on the experi- 

 mental stream was established approximately 

 one -half mile below the spray area to deter- 

 mine whether the kill extended any distance 

 below the spray area . Observations by Hoff- 

 mann and Surber (1949) and Surber and Friddle 

 (1947) indicated that the kill due to the accumu- 

 lative effect is greater immediately below the 

 spray area and carries quite some distance 

 downstream . In this study, however, the kill 

 was less pronounced, as can be seen from Sta- 

 tion 3 (table 6). This is probably due to the 

 rapid increase in water volume in streams of 

 this nature. 



In the same stream in 1960 (table 7) 

 the mayflies, stoneflies and caddisflies were 

 moderately reduced in the treated stream after 

 72 hours, while invertebrates in the control 

 stream were, in general, not reduced in 

 number. 



DISCUSSION 



Seldom would one find an area more dif- 

 ficult to treat than the sharply pointed peaks 

 and deep ravines with adverse wind currents 

 that were encountered in these areas . Yet, in 

 the Conasauga Lake area, the special care taken 

 to keep spray from entering the creek was suc- 

 cessful. Such small amounts of DDT entered 

 the stream that there was no significant loss of 

 aquatic organisms. This suggests that with 

 greater care in the application of insecticides, 

 kills of aquatic organisms may be minimized. 



Figure 3 points up an important reaction 

 of the depleted aquatic invertebrate population . 

 In all cases the population dropped between the 

 pre -treatment and post-treatment sampUng; 

 however, the treated areas dropped considerably 



more. The general decrease in the population 

 was probably due to emergence, as was shown 

 by Anderson and Hooper (1956) and Ball and 

 Hayne (1952) in studies of seasonal fluctuation 

 of bottom fauna. Both of these studies indicated 

 a decrease in bottom fauna population starting 

 soon after the disappearance of the ice cover 

 and proceeding until July. At that time the pop- 

 ulation density began to increase . The greater 

 decrease witnessed in the treated area in the 

 present study was undoubtedly due to the effect 

 of the DDT which entered the stream. Imme- 

 diately after treatment large numbers of stone- 

 flies and lesser numbers of mayflies and caddis- 

 flies appeared in drift samples . One hour after 

 treatment, mayflies appeared in the greatest 

 numbers while stoneflies and caddisflies de- 

 creased and midges increased slightly. Two 

 hours after treatment, midge numbers were 

 still increasing while all other forms were de- 

 creasing in number. It is interesting to note 



Figure 3. --Numbers of aquatic invertebrates 

 sampled in the experimental and control streams 

 on Brasstown Bald in 1959. 



8 



