Volumen 45 - Número 1: 1-18 | 2010
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The microbial community in the coastal upwelling system off Concepción, Chile, 36°S, 2002-2003 period

Yoanna Eissler^1,2*, Jaime Letelier^3,4, L. Antonio Cuevas⁵, Carmen E. Morales⁶ and Rubén Escribano⁶

¹Centro de Investigación y Gestión de Recursos Naturales, Departamento de Química y Bioquímica, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretaña 1111, Valparaíso, Chile

²CIEN Austral, Centro de Investigación en Nutrición, Tecnología de Alimentos y Sustentabilidad, Universidad Austral de Chile, Los Pinos S/N, Balneario Pelluco, Casilla 1327, Puerto Montt, Chile

³Programa de Postgrado en Oceanografía, Universidad de Concepción, Casilla 160-C, Concepción, Chile

⁴Escuela de Ciencia del Mar, Pontificia Universidad Católica de Valparaíso, Av Altamirano 1480, Valparaíso, Chile

⁵Department of Biology, University of Bergen, Thormøhlens gate 53, PO Box 7003, N-5020 Bergen, Norway

⁶Centro de Investigaciones Oceanográficas del Pacífico Sur-Oriental (COPAS), Estación de Biología Marina, Departamento de Oceanografía, Universidad de Concepción, Casilla 44, Dichato, Chile

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This study describes the abundance and vertical distribution of microbial assemblages (from femto to nanoplankton) in the upwelling area off Concepción (~36ºS), analyses their relationship to oceanographic conditions during the upwelling season (austral spring-summer: December 2002- March 2003), and explores microbial community interrelationships; at one shelf station and at the shelf break off the Southeastern Pacific coast. Virioplankton (VP), bacterioplankton (BP), and autotrophic (ANF) and heterotrophic (HNF) nanoflagellates were enumerated by epifluorescence microscopy. Abundances of VP, BP, HNF and ANF ranged as follows: 0.04-13.9 x 10⁷ virus like particles mL^-1, 0.5-5.6 x 10⁶ , 0.016- 0.4 x 10³, and 0.08-0.6 x 10³ cells mL^-1, respectively. Variability in VP, BP and HNF abundance was explained in less than 27% by the oceanographic setting (i.e., temperature, salinity and dissolved oxygen). Upwelling conditions have a significant effect on distribution and abundance only of VP in both station examined. VP abundance was significant and positively related to the abundances of BP, ANF and HNF, suggesting that they may be possible hosts of marine viruses. Furthermore, the VP/BP ratio (mean= 9) obtained represented the upper limit of literature values, suggesting a high interaction between virioplankton and bacterioplankton.

Key words: Viruses, bacterioplankton, nanoplankton, microbial assemblages