Bottom-up and top-down control of bacterioplankton from eutrophic to oligotrophic sites in the tropical northeastern Atlantic Ocean

• Published in: Deep-sea research. Part I, Oceanographic research papers Vol. 43; no. 8; pp. 1305 - 1320
• Main Authors: Dufour, P.H., Torréton, J.-P.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.1996; Pergamon Press Inc
• Subjects: Bacteria; Marine; Oceanography; Oceans; Plankton; Atlantic Ocean; ASE, Atlantic
• ISSN: 0967-0637; 1879-0119
• DOI: 10.1016/0967-0637(96)00060-X

Bacterioplankton biomass and production were determined over the whole water column of a eutrophic, a mesotrophic and an oligotrophic site (2300, 3200 and 4500 m deep) in the tropical NE Atlantic Ocean during a EUMELI cruise in May–June 1992. This resulted in an exceptionally large amplitude of data, with abundance, biomass and production ranging from 1.2 × 10 7 to 3.9 × 10 9 cell 1 −1, 1.2 × 10 −7 gC1 −1 to 4.7 × 10 −5 gC1 −1 and 2.0 × 10 −11 gC1 −1 h −1 to 9.6 × 10 −7 gC1 −1 h −1, respectively. These data were analyzed in order to determine whether bacterioplankton was controlled by bottom-up or top-down processes. Regressions of log-transformed bacterioplankton biomass versus log-transformed production were tested at the different sites and in different layers. Slopes of 0.40–0.55 suggest that bacterioplankton is moderately controlled by bottom-up processes increasing from the eutrophic coastal site to the open ocean oligotrophic site and from surface layers (< 250 m) to deep waters. These conclusions are in agreement with other indices of bottom-up control like cell size, doubling times of the biomass, per cent of active cells, and relationships of bacterial biomass versus phytoplanktonic biomass and production.