| The objective of this research was to determine if physical and microbial sediment characterizations could be used to explain benthic macroinvertebrate distribution in two branches of Lake Ray Roberts, Texas. In the past, abiotic characteristics of the sediment such as particle size and organic matter content have been correlated with macroinvertebrate distribution, as has microbial density. However, microbial activity, a measure of organic matter quality and possible nutritional value has not been considered.; In this study, the heterogeneity of sediment characteristics including particle size, organic matter, and moisture content were analyzed, and their relationship to macrobenthic and microbenthic distribution evaluated. Secondly, the activity of three microbial enzymes, {dollar}beta{dollar}-glucosidase, {dollar}beta{dollar}-galactosidase, and phosphatase were determined and correlated to macrobenthic distribution. Pairwise correlation analysis and multivariate statistical techniques including cluster analysis, bootstrapping, cophenetic correlation, and multiple regression analysis were then employed in an attempt to understand these relationships. Pairwise correlation analysis of macroinvertebrate distribution indicated statistically significant ({dollar}alpha{dollar} = 0.10) relationship with particle size organic matter content, and enzyme activity as did cluster analysis. However, multiple regression analysis using several biotic and abiotic factors failed to account for more than 30% of the variance in the macrobenthic distribution model.; Ecologically, clear relationships were observed between individual macrobenthic organisms and particle size, microbial enzyme activity and organic matter. These results suggested that microbial enzyme activity may play an important role in macrobenthic distribution. Furthermore, recent studies have indicated that microbial enzyme activities vary with organic matter particle size and type. Because macrobenthic community structure and microbial activity and density have each been correlated with particle size, a logical next step in this research would be to evaluate microbial community characteristics along a particle size gradient. Such research might further the understanding of trophic interactions that regulate both communities. |
