Release and bioavailability of C, N, P Se, and Fe following viral lysis of a marine chrysophyte

Abstract

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 anophagefferens. Photochemical effects on the dissolved‐particulate partitioning and biological uptake of virally released elements were also investigated. Viral lysis of A. anophagefferens 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. anophagefferens and bacterial densities, as well as an increase in particulate organic nitrogen levels in cultures during viral lysis. These observations indicate that 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 dissolved 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 bioavailabiliity of virally released Se to diatoms, while decreasing the bioavailability of C to bacteria threefold. The viral lysis of an A. anophagefferens bloom in the field could release 40 µ M 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.