The individual size distribution (ISD), also known as size spectra, describes the relationship between body mass and abundance, independent of species identity. ISDs are widely used to characterize community structure and infer energy flow within aquatic food webs. However, accurately estimating ISDs is challenging because common macroinvertebrate sampling methods introduce size-dependent biases. These biases can distort our understanding of individual sizes and lead to inaccurate estimates of community-level density and biomass, ultimately affecting interpretations of ecosystem structure and function. Power law models have been developed to estimate undersampled portions of the size spectrum, yet few studies explicitly apply these models to correct biased field datasets. In this study, benthic macroinvertebrate data from Brule Creek, SD is used to estimate a power law model and extrapolate undersampled sizes, with the goal of generating more accurate estimates of community biomass. Preliminary analyses indicate substantial undersampling, sometimes exceeding 50% of the data. We will examine how power-law corrections change community biomass compared to the original data. Differences in ISD slopes and biomass estimates will be used to evaluate how missing size classes influences overall community patterns.