RELEASE AND BIOAVAILABILITY OF C, N, P, SE, AND FE FOLLOWING VIRAL LYSIS OF A MARINE CHRYSOPHYTE

The potential importance of the viral lysis of phytoplankton for nutri ent and carbon cycling has been acknowledged, but no quantitative asse ssments of this phenomenon exist. Radiotracer experiments examined the release and bioavailability of C, N, P, Fe, and Se following viral ly sis of the ''brown tide'' chrysophyte Aureococcus anophagefferens. Pho tochemical effects on the dissolved-particulate partitioning and biolo gical uptake of virally released elements were also investigated. Vira l lysis of A. anophagefferens released 50% mon C and Se than uninfecte d control cells to the dissolved phase, while N, P, and Fe remained in the particulate phase. There was a significant inverse correlation be tween A. anophagefferens and bacterial densities, as well as an increa se in particulate organic nitrogen levels in cultures during viral lys is. These observations indicate that released dissolved organic matter supported bacterial growth and may be a pathway by which various elem ents are diverted in microbial food webs. Dissolved nutrients released by viral lysis were accumulated to varying degrees by natural assembl ages of marine bacteria and cultured diatoms, and vitally 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 bioa vailability of virally released Se to diatoms, while decreasing the bi oavailability of C to bacteria threefold. The viral lysis of an A. ano phagefferens bloom in the field could release 40 mu M dissolved organi c carbon and rapidly transfer other released elements to bacteria. Suc h occurrences may significantly affect water column chemistry, species composition, and succession within marine plankton communities.