Spectral irradiance and pigment (porphyrin and carotenoid) measurements were made across strong frontal boundaries of the Gulf Stream in the northwest Atlantic. Upwelling and downwelling irradiance were measured at 2-nanometer (nm) increments across the visible spectrum (400-700 nm). Pigment concentrations were determined by high performance liquid chromatography (HPLC). The irradiance spectra suggest that passive fluorescence occurs in frontal waters. The phytoplankton pigment composition showed significant changes across the frontal region. Pigment changes are reflected in the spectral attenuation coefficients, even at low pigment concentrations measured in Gulf Stream waters. Application of the spectral attenuation coefficient suggests an alternate method for accessing the pigment character in surface waters. The surface pigment distribution aids in our understanding the ocean color variability measured with satellite sensors.