Pelagic food web patterns: do they modulate virus and nanoflagellate effects on picoplankton during the phytoplankton spring bloom?

摘要: Summary As agents of mortality, viruses and nanoflagellates impact on picoplankton populations. We examined the differences in interactions between these compartments two French Atlantic bays. Microbes, considered here as central actors planktonic food web, were first monitored seasonally Arcachon (2005) Marennes-Oleron (2006) Their dynamics evaluated to categorize trophic periods using models Legendre Rassoulzadegan a reference framework. Microbial then compared through 48 h batch culture experiments performed during phytoplankton spring bloom, identified herbivorous Marennes multivorous Arcachon. was spatially homogeneous with The former potentially more productive, featuring large number heterotrophic pathways, while autotrophic mechanisms dominated A link found Marennes, suggesting role virus regulation autotroph biomass. Moreover, virus–bacteria relation weaker bacterial lysis potential 2.6% 39% (based size-fractionation viral enrichment) revealed different microbial that corresponded spring-bloom each bay. In Arcachon, where there is flagellate predation acted an opposite way picophytoplankton. When together they both reduced production. Conversely, (herbivorous web), flagellates increased Differences composition community explained combined flagellate-virus effects production