The sensing and subsequent remediation of environmental pollutants in waterways is critical to maintaining a healthy ecosystem. Sea lettuce (Ulva lactuca) acts as a natural bioaccumulator of heavy-metal pollutants in seawater, increasing concentrations up to 100-fold. We are developing sensors based on the intrinsic fluorescence of single-walled carbon nanotubes functionalized to detect heavy-metal ions that enter sea lettuces and report the localized analyte concentrations.