TY - CONF
T1 - Oxygen consumption and labile dissolved organic carbon uptake by benthic biofilms
AU - de Falco, Natalie
AU - Boano, Fulvio
AU - Arnon, Shai
PY - 2015/4/1
Y1 - 2015/4/1
N2 - Biogeochemical activity in streams is often magnified at interfaces,
such as in the case of biofilm growth near the surface of the stream
sediments. The objective of this study was to evaluate the relative
importance of surficial biofilms versus the biofilm in the hyporheic
zone to the processes of biodegradation of a labile dissolved organic
carbon (DOC) and to oxygen consumption. Experiments were conducted in a
recirculating flume, equipped with a drainage system that enables the
control on losing and gaining fluxes. A surficial biofilm was developed
over a sandy streambed with dune-shaped bed forms, by providing labile
DOC (sodium benzoate) and nitrate. Homogeneously distributed biofilm was
obtained by the same feeding strategy but with mixing the sediments
manually on a daily basis. After the biofilm growth period,
transformation of the labile DOC under different overlying velocities
and losing or gaining fluxes was studied after spiking with sodium
benzoate and by monitoring the decrease in DOC concentration in the bulk
water over time using an online UV/Vis spectrophotometer. In addition,
oxygen profiles across the water-streambed interface were measured at
different locations along the bed form using oxygen microelectrodes.
Preliminary results showed that the rate of labile DOC degradation
increased exponentially with increasing overlying water velocity,
regardless of the type of biofilm. Gaining and losing conditions did not
play a critical role in the DOC degradation regardless of the type of
biofilm, because the labile DOC was quickly utilized close to the
surface. Under losing conditions, complete depletion of oxygen was
observed within the top 5 millimeters, regardless of the biofilm type.
In contrast, oxygen profiles under gaining condition showed an
incomplete consumption of oxygen followed by an increase in the
concentration of oxygen deeper in the sediments due to the upward flow
of oxygenated groundwater. The results suggest that the transformation
of labile DOC occurs in the upper millimeters of the streambed, and the
size and shape of the hyporheic flow paths are less important for
aerobic activity. In addition, the effect of overlying water velocity on
labile DOC transformation was shown to be more influential than losing
and gaining fluxes.
AB - Biogeochemical activity in streams is often magnified at interfaces,
such as in the case of biofilm growth near the surface of the stream
sediments. The objective of this study was to evaluate the relative
importance of surficial biofilms versus the biofilm in the hyporheic
zone to the processes of biodegradation of a labile dissolved organic
carbon (DOC) and to oxygen consumption. Experiments were conducted in a
recirculating flume, equipped with a drainage system that enables the
control on losing and gaining fluxes. A surficial biofilm was developed
over a sandy streambed with dune-shaped bed forms, by providing labile
DOC (sodium benzoate) and nitrate. Homogeneously distributed biofilm was
obtained by the same feeding strategy but with mixing the sediments
manually on a daily basis. After the biofilm growth period,
transformation of the labile DOC under different overlying velocities
and losing or gaining fluxes was studied after spiking with sodium
benzoate and by monitoring the decrease in DOC concentration in the bulk
water over time using an online UV/Vis spectrophotometer. In addition,
oxygen profiles across the water-streambed interface were measured at
different locations along the bed form using oxygen microelectrodes.
Preliminary results showed that the rate of labile DOC degradation
increased exponentially with increasing overlying water velocity,
regardless of the type of biofilm. Gaining and losing conditions did not
play a critical role in the DOC degradation regardless of the type of
biofilm, because the labile DOC was quickly utilized close to the
surface. Under losing conditions, complete depletion of oxygen was
observed within the top 5 millimeters, regardless of the biofilm type.
In contrast, oxygen profiles under gaining condition showed an
incomplete consumption of oxygen followed by an increase in the
concentration of oxygen deeper in the sediments due to the upward flow
of oxygenated groundwater. The results suggest that the transformation
of labile DOC occurs in the upper millimeters of the streambed, and the
size and shape of the hyporheic flow paths are less important for
aerobic activity. In addition, the effect of overlying water velocity on
labile DOC transformation was shown to be more influential than losing
and gaining fluxes.
M3 - תקציר
SP - 243
ER -