Effect of the contribution of nitrogen and dissolved organic matter derived from salmon farming on the bacterioplanctonic diversity in the town of Puyuhuapi, North Patagonia.. Bacterioplankton response to dissolved organic matter in fjords

Salmon farming releases significant amounts of organic matter to the water column. A portion of this organic matter would correspond to salmon mucus, which is continuously released, acting as a protective barrier and remaining available as potential substrate for microbial communities in the water column. In order to understand this source of organic matter the different excreted components must be analyzed and the mucus generated in the salmon cultures is an important part of this excretion. A study was carried out in the Puyuhuapi fjord (Puerto Cisnes), where two experiments of 24 hours were carried out at 2m and 100m depth. The objective was to understand the potential effect of mucus on microbial assembleges and the input of mucus via natural microbial formations in waters surrounding the salmon farming centers and evaluate NH4+ production and degradation of dissolved organic material. For this purpose, nutrient concentrations (NH4+, NO3-), dissolved organic carbon (COD), picoplankton abundance and diversity were analyzed. The results showed variations in ammonium concentration, bacterial abundance (55% decrease in the control treatment at 24 hours in the experiment 2 meters deep) and COD among treatments inoculated with mucus in relation to the control at 2m depth. Changes in the community structure were observed, varying their equity (minimum: 0.32 maximum: 0.51) and diversity (minimum: 1.67 maximum: 2.09) as a response to mucus inoculum, varying the contribution percentages of Bacteroidetes, gammaproteobacterias and α-Proteobacteria due to the consumption generated by the available ammonium. The aggregate concentrations of mucus to 2m did not generate prolonged changes in the concentrations observed in the experiment. The microbial community structure was stabilized after T24 At 100 m depth, although there are changes in the community structure till T12, the patterns of increase in the variables remain similar between the treatments. The contribution percentage of the class gammaproteobacteria, which has characteristics capable of degrading organic matter Nitrogen by assisting the remineralization of nitrogen and assimilating ammonium without reducing it. Therefore, the mucus adhered to the system show alterations in the bacterial contribution in both treatments and in the ammonium concentration in both Experiments, of the system in the water column.