Virioplankton dynamics and virally induced phytoplankton lysis versus microzooplankton grazing southeast of the Kerguelen (Southern Ocean)

• Published in: Deep-sea research. Part II, Topical studies in oceanography Topical studies in oceanography, 2008-01, Vol.55 (5), p.752-765
• Main Authors: Brussaard, C.P.D., Timmermans, K.R., Uitz, J., Veldhuis, M.J.W.
• Format: Article
• Language: English
• Subjects: 48–52°S and 72–78°E; Bacteria; Copepoda; Distribution; Earth Sciences; Grazing; Kerguelen Plateau; Lysis; Marine; Oceanography; Phytoplankton; Sciences of the Universe; Southern Ocean; Viruses
• ISSN: 0967-0645; 1879-0100
• DOI: 10.1016/j.dsr2.2007.12.034

Viral dynamics, community structure, and the impact of viruses on phytoplankton mortality in comparison with microzooplankton grazing were determined in the natural iron-fertilized waters southeast of the Kerguelen Islands, Southern Ocean, during the austral summer (January–February 2005). The study area was characterized by a phytoplankton bloom above the Kerguelen Plateau and the high-nutrient low-chlorophyll waters surrounding it. During the Kerguelen Ocean and Plateau compared Study (KEOPS), viral abundance was relatively high (1–19×10 7 mL −1) as compared to the few other studies in the Southern Ocean, significantly correlating with depth and system productivity. Viral abundance showed a strong positive relationship with the numerically dominant bacterial hosts, which in turn were correlated to phytoplankton biomass. In total, 13 different viral genome sizes were detected, with the lower-sized genomes 34 and 68 kb dominating at all stations. The viral community at the low chlorophyll C-transect grouped apart from the more productive transects A and B. Potential algal viruses were recorded for all stations, but only at very low intensities. Virally induced lysis of the smaller-sized (