The bacterial communities of the Río Negro estuary in the Argentinian Patagonia were studied to understand the effect of wetland outwelling and tides on their composition and to assess bacterial links with biogeochemical markers and nutrient dynamic. Estuarine water was collected every hour across a tidal cycle at two locations: a channel directly connected to an extensive wetland and a sampling station located in the middle of the estuary. Estuarine water was filtered through 0.2 µm and 5 µm membranes to characterize free-living and particle-attached communities. Sediments were sampled at the wetland to appraise the likely effect of sediment resuspension on free-living and particle-attached communities.