Short-term temporal variations of heterotrophic bacterial abundance and production in the open NW Mediterranean Sea

G. Mével (1) , Marc Vernet (1) , J. F. Ghiglione (2)

1 AD2M - Adaptation et diversité en milieu marin
2 LOBB - Laboratoire d'océanographie biologique de Banyuls

We present the vertical and temporal dynamics of total vs. particle-attached bacterial abundance and activity over a 5 week period under summer to autumn transition in NW Mediterranean Sea. By comparison to previous investigations in the same area but during different seasons, we found that total bacterial biomass and production values were consistent with the hydrological conditions of the summer-fall transition. At a weekly time scale, total bacterial biomass and production in the euphotic layers was significantly correlated with phytoplanktonic biomass. At an hourly time scale, total bacterial biomass responded very rapidly to chlorophyll-a fluctuations, suggesting a tight coupling between phytoplankton and bacteria for resource partitioning during summer-autumn transition. In contrast, no influence of diel changes on bacterial parameters was detected. Episodic events such as coastal water intrusions had a significant positive effect on total bacterial abundance and production, whereas we could not detect any influence of short wind events whatever the magnitude. Finally, we show that particle-attached bacteria can represent a large proportion (until 49%) of the total bacterial activity in the euphotic layer but display rapid and sporadic changes at hourly time scales. This study underlines the value of large datasets covering different temporal scales to clarify the biogeochemical role of bacteria in the cycling of organic matter in open seawater.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

G. Mével, Marc Vernet, J. F. Ghiglione. Short-term temporal variations of heterotrophic bacterial abundance and production in the open NW Mediterranean Sea. Biogeosciences Discussions, 2008, 5 (3), pp.1899-1932. ⟨hal-00330299⟩