The potential importance of the viral lysis of phytoplankton for nutrient and carbon cycling has been acknowledged, but no quantitative assessments of this phenomenon exist. Radiotracer experiments examined the release and bioavailability of C, N, P Fe, and Se following viral lysis of the "brown tide" chrysophyte Aureococcus anophagefSeerens. Photochemical effects on the dissolved-particulate partitioning and biological uptake of virally released elements were also investigated. Viral lysis of A. anophagefSerens released 50% more C and Se than uninfected control cells to the dissolved phase, while N, P, and Fe remained in the particulate phase. There was a significant inverse correlation between A. unophugefirens and bacterial densities, as well as an increase in particulate organic nitrogen levels in cultures during viral lysis. These observations indicate thitt released dissolved organic matter supported bacterial growth and may be a pathway by which various elements are diverted in microbial food webs. Dissolved nutrients released by viral lysis were accumulated to varying degrees by natural assemblages of marine bacteria and cultured diatoms, and virally regenerated N and P relieved diatom nutrient limitation. During a 4-wk incubation, 80% of C and P within cell lysis debris was released to the diss,olved phase, likely due to bacterial activity. Photochemical degradation of cell lysis debris enhanced dissolved levels of Se (100%) and Fe (50%) and reduced total dissolved C by 15%. Photochemistry doubled the bioavailability of virally released Se to diatoms, while decreasing the bioavailability of C to bacteria threefold. The viral lysis of an A. unophugefirens bloom in the field could release 40 PM dissolved organic carbon and rapidly transfer other released elements to bacteria. Such occurrences may significantly affect water column chemistry, species composition, and succession within marine plankton communities.

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Viruses have been hypothesized to control blooms of Aureococcus anophagefferens gen. et sp. nov. (Chrysophyceae), a marine phytoplankton that since 1985 has caused devastating summer blooms called "brown tide." By means of ultrafiltration methods, viruses specific to this alga were isolated from both the Great South Bay and Peconic Bay systems of Long Island, New York, during the summer bloom period of 1992. Cell lysis of healthy algal cultures was demonstrated, as well as continuing reinfection with serial transfers of cultures. Electron microscope surveys yielded images of phage-like virus particles with tails that could attach to A. anophagefferens cells within minutes of exposure. The isolation and cultivation of this virus highlights the need for further study of viral infection of eukaryotic algae and the potential for a better understanding of algal bloom control by viral infection.

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