Water samples from Great South Bay, New York, contained biological agents capable of causing the lysis of the brown-tide alga Aureococcus anophagefferens Hargraves et Sieburth. From these water samples, 32 bacterial isolates were tested for algicidal effects against the algae. Six of the isolates were shown to have algicidal effects against A. anophagefferens. Sequencing of the gene 16S rRNA revealed that the isolates were relatively diverse. Based on their similarity to sequences in repositories, the isolates seem to be closely related to Bacillus, Halomonas, Croceibacter atlanticus, Marinobacter, and an Arctic deep-sea bacterium.