La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Changes in Nutrient and Carbon Availability and Temperature as Factors Controlling Bacterial Growth in the Northern Baltic Sea
Auteurs :	Laura Hoikkala, Auteur ; Hanna Aarnos, Auteur ; Risto Lignell, Auteur
Type de document :	Article
Dans :	Estuaries and Coasts (32(4) JUL 2009)
Article en page(s) :	720-733
Résumé :	The effects of inorganic nutrient (N and P) and glucose C treatments on bacterial growth were followed for 3 days in natural surface and deep water bacterial samples during the main post-spring bloom stages of phytoplankton growth in the northern Baltic Sea. In addition, the importance of photochemical degradation of dissolved organic matter on bacterial growth was investigated vertically (0.1-2.0 m) and spatially, in a salinity gradient from river mouth to open sea. Bacterial production was consistently C limited in the surface layer, with N or both N and P as the secondary limiting nutrients from spring to early summer and in late summer, respectively. In deep water, bacterial growth showed combined temperature and C limitation, and in spring, this also appeared to be true with surface samples. The effect of 1-day sunlight pre-treatment varied from no effect up to a 44% production increase, with clear bacterial production responses only being seen at the surface (10 cm depth). The implications of bacterial C limitation for the structure and function of the surface plankton ecosystem, including its CO(2) exchange with the atmosphere are discussed.

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