We applied two numerical methods to in situ hyperspectral measurements of remote sensing reflectance R_rs to assess the feasibility of remote detection and monitoring of the toxic dinoflagellate, Karenia brevis, which has been shown to exhibit unique absorption properties. First, an existing quasi-analytical algorithm was used to invert remote sensing reflectance spectra, R_{\text{rs}}\left(\lambda \right) , to derive phytoplankton absorption spectra, a_{\phi }^{R\text{rs}}\left(\lambda \right) . Second, the fourth derivatives of the a_{\phi }^{R\text{rs}}\left(\lambda \right) spectra were compared to the fourth derivative of a reference K. brevis absorption spectrum by means of a similarity index (SI) analysis. Comparison of reflectance-derived a_{\phi } with filter pad measured a_{\phi } found them to agree well (R^2=0.891 ; average percentage difference, 22.8\%) . A strong correlation \left(R^2=0.743\right) between surface cell concentration and the SI was observed, showing the potential utility of SI magnitude as an indicator of bloom strength. A sensitivity analysis conducted to investigate the effects of varying levels of cell concentrations and colored dissolved organic matter (CDOM) on the efficacy of the quasi-analytical algorithm and SI found that a_{\phi }^{R\text{rs}}\left(\lambda \right) could not be derived for very low cell concentrations and that, although it is possible to derive a_{\phi }^{R\text{rs}}\left(\lambda \right) in the presence of high CDOM concentrations, CDOM levels influence the a_{\phi }^{R\text{rs}}\left(\lambda \right) amplitude and shape. Results suggest that detection and mapping of K. brevis blooms based on hyperspectral measurements of R_{\text{rs}} are feasible.