Benthic fluxes and nitrate reduction activity in a marine park (Northern San Jorge Gulf) from Patagonia Argentina

ESTEVES, JOSÉ LUIS; FALESCHINI, MAURICIO; TORRES, AMÉRICO IADRAN

Environmental Earth Sciences

Springer

Lugar: Alabama; Año: 2016 vol. 75 p. 1 - 9

The Northern San Jorge Gulf (NSJG) wasdeclared Coastal Marine Park in 2008 with the goal ofpreserving its biodiversity. In situ benthic fluxes experimentswere performed using an opaque chamber in SaraCreek (SC) and Malaspina Creek (MC). Moreover, ex situnitrate reduction activity was assessed using a continuousflow-through system. Benthic fluxes in MC, showed aconsumption of oxygen (794 ± 196 mg m-2 h-1)and nitrate (103 ± 68 lmol m-2 h-1) by sediment andrelease of ammonium (175 ± 60 lmol m-2 h-1), phosphate(66 ± 10 lmol m-2 h-1) and silicate (116 ±66 lmol m-2 h-1) towards the water column. In SC, thesame pattern was observed and the fluxes values were375 ± 132, 128 ± 1, 76 ± 12, 39 ± 24 and 133 ± 81,respectively. Only, ammonium and oxygen fluxes showedsignificant differences between sites, due to the highestorganic matter content and the particular hydrodynamicconditions in MC. These are the first benthic flux measurementsmade within the protected area. Nitrate uptakerate, based on Michaelis?Menten kinetic, was Km:155.3 lM and Vmax: 0.053 lM g-1 h-1 in SC and Km:131.2 lM and Vmax: 0.039 lM g-1 h-1 in MC. Consideringthe nitrate dynamic we concluded that the sedimentsboth SC and MC act as a sink of nitrate. This ion could beprincipally used as a terminal electron acceptor during theoxidation process of organic compounds in sediments ofNSJG.