Environmental sequencing has revealed unimagined diversity among eukaryotic picoplankton. Here, a distinct picoplanktonic algal group (table S1), initially detected from 18S rDNA sequences, was hybridized with rRNA probes, detected by Tyramide Signal Amplification - Fluorescent In Situ Hybridization (TSA-FISH) and showed an organelle-like body with orange fluorescence indicative of phycobilins. Using this fluorescence signal, cells were sorted by flow cytometry and probed. Hybridized cells contained a DAPI staining organelle resembling a plastid with a nucleomorph. This suggests that they may be secondary endosymbiotic algae. Pending isolation of living cells and their formal description these algae have been termed picobiliphytes.