LITTORAL BENTHOS OF BELEWS LAKE 585 



Department of Biostatistics time-sharing library, University of North 

 Carolina. The basic analysis makes comparisons among years and 

 between stations groups. The two groups were main lake (M) and 

 discharge (D) stations. Occasionally a subset of the M group, termed 

 upper main lake (U), is used (stations 65M, 8, 4, 1907, and 2). 

 Because the station— date interactions frequently confounded analy- 

 sis of between-year differences, only the yearly averages for stations 

 could be compared. 



For each dominant organism a 3 by 2 matrix was set up, showing 

 the yearly standing-crop averages for both M and D stations over 

 years 4 to 6, and F tests were run to check significant differences 

 among years and between station groups. Years were compared by a 

 simple two-way analysis of variance that used both year and station 

 as variables. Comparing station groups was more difficult since an 

 arbitrary pairing of stations was not possible. Therefore, the values 

 within each station group were rank-ordered and station serves as a 

 dummy variable. A minimum of seven F tests were performed for 

 each 3 by 2 matrix. 



For all dominant organisms, F tests were performed to assess 

 both the differences between discharge (D) stations and main lake 

 (M) stations and the differences among years. It was necessary to 

 define a series of analysis criteria to facilitate comparisons among 

 years. These criteria are: 



1. Stability, No significant difference exists among years for 

 either station group, or the significant difference is slight (< 20/m*^ ). 



2. Convergence. A significant difference exists between station 

 groups for the first year but not for the second. 



3. Colonization or succession. A significant difference exists 

 among years for both station groups. If there is a consistent 

 difference between M and D stations, the change is proportionally 

 equal (parallel change). 



4. Power-plant effect. 



a. No significant difference exists among years for M stations, 

 but there is a significant difference among years for D stations. 



b. A significant difference exists between basins for both 

 years. The increase or decrease among years for the two basins is not 

 proportionally equal (nonparallel change). 



RESULTS AMD DISCUSSIOIM 



Approximately 150 taxa were recorded in littoral samples from 

 Belews Lake in year 4 to year 6. Twenty -three of the most abundant 

 taxa were subjected to statistical analysis and were evaluated 



