The deep chlorophyll maximum (DCM) is a marine water-layer that is richer in phytoplankton than other layers, with relatively high rates of inorganic carbon assimilation. It is generally located towards the base of the thermocline in lakes and oceans during the stratification period. The increased carbon availability in this zone, as a consequence of photosynthetic activity, can affect the heterotrophic microbial assemblage (HMA). The aim of this work is to study how changes in depth and abundance of chlorophyll in DCM, and therefore in the available carbon, can affect the structure of the associated HMA. In the framework of the MEDIMAX project, Mediterranean seawater was collected from the vertical profile (up to 2,000 m) off the coast of Alicante, Spain, then used for experiments where the availability of DOC was manipulated. Water for the experiments was collected from a depth of 30 m where the CTD recorded the main DCM. The experimental procedure consisted in a factorial design with three replicates and two studied factors, the first factor was binary (light-darkness) while the second factor was carbon availability and presented 7 levels (1/4x,1/2x, Control without modifications, 2x, 4x, 16x, 32x) with respect to the original concentration. Microbial assemblages of the main bacteria that constitute DCM was determined by FISH, covering total bacteria as well as the most abundant groups of heterotrophic bacteria according to metagenomic determinations (Alpha-proteobacteria, SAR11, Beta-proteobacteria, Gamma-proteobacteria, Actinobacteria, - and specifically the ultra-small Actinomarinaminuta-, Bacteroidetes and Firmicutes). Maximum bacterial abundance within the vertical profiles was found at 30 meters, coinciding with the DCM. Experimental results show a significant increase in bacterial abundance associated with increased available carbon as well as changes in population structure.
Experimental approach to the effect of available carbon as a structuring factor for microbial populations in the Mediterranean Deep Chlorophyll Maximum.
Lo Giudice A;
2017
Abstract
The deep chlorophyll maximum (DCM) is a marine water-layer that is richer in phytoplankton than other layers, with relatively high rates of inorganic carbon assimilation. It is generally located towards the base of the thermocline in lakes and oceans during the stratification period. The increased carbon availability in this zone, as a consequence of photosynthetic activity, can affect the heterotrophic microbial assemblage (HMA). The aim of this work is to study how changes in depth and abundance of chlorophyll in DCM, and therefore in the available carbon, can affect the structure of the associated HMA. In the framework of the MEDIMAX project, Mediterranean seawater was collected from the vertical profile (up to 2,000 m) off the coast of Alicante, Spain, then used for experiments where the availability of DOC was manipulated. Water for the experiments was collected from a depth of 30 m where the CTD recorded the main DCM. The experimental procedure consisted in a factorial design with three replicates and two studied factors, the first factor was binary (light-darkness) while the second factor was carbon availability and presented 7 levels (1/4x,1/2x, Control without modifications, 2x, 4x, 16x, 32x) with respect to the original concentration. Microbial assemblages of the main bacteria that constitute DCM was determined by FISH, covering total bacteria as well as the most abundant groups of heterotrophic bacteria according to metagenomic determinations (Alpha-proteobacteria, SAR11, Beta-proteobacteria, Gamma-proteobacteria, Actinobacteria, - and specifically the ultra-small Actinomarinaminuta-, Bacteroidetes and Firmicutes). Maximum bacterial abundance within the vertical profiles was found at 30 meters, coinciding with the DCM. Experimental results show a significant increase in bacterial abundance associated with increased available carbon as well as changes in population structure.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
