|Microheterotrophic communities in the water column of the Rhone river plume|
|Soto, Y.; Bianchi, M. (1990). Microheterotrophic communities in the water column of the Rhone river plume. Mar. Nat. 3: 37-42|
|In: Marine Nature. Marine Science Institute, Yeungnam University: Kyongsan. ISSN 1225-990X, more|
As tidal range is very small in the Mediterranean, the Rhone River plume (1600m3 s• 1) spreads as a thin layer of low density water over the seawater. Schematically, the water column of the plume area is constituted by three layers. The upper freshwater layer is about 1-1.5m deep and carries heavy loads of organic and mineral particles as well as dissolved components. The intermediate layer, of 0.5-lm, is a discontinuity zone, showing strong density and dissolved nutrients gradients. The third layer, seawater, receives mostly particles from the other layers. In the Rhone water layer, as well as in the seawater, bacterial production and biomass are relatively constant, whatever more important in the freshwater. The three superposed layers showed three distinct microbial communities. The river water community is composed of freshwater bacteria, with low activity. The interface layer community can be described as a juvenile community of oligotrophic marine bacteria. The marine water community was characterized by low numbers of bacteria with growth limited by organic substrate availability.