180
A. Accornero et al.
min. Physical parameters were monitored by means of two Aanderaa RCM7
current meters with thermistor and conductive cells placed at 244- and 390-m
depth, two SBE Seacats with température and conductivity recorders positioned at 243 and 398 m, and one Aanderaa RCM7 current meter with only a
thermistor sensor located 20 m above the sea floor. An RDI ADCP current
meter profiler was fixed at the top of the mooring array to measure the upper
layer velocity, but it did not work, due to battery power failure.
2.2 Océanographie Time Sériés Data Analysis
Time sériés of currents, température and salinity measurements, acquired
every 30 min, were filtered and averaged. The averages were computed on several time intervals (1, 5, 10, 15 and 30 days) to highlight the behaviour of the
considered variables on different time scales. Vertical objective analysis [15]
was performed with the aim of reconstructing the temporal évolution of the
vertical profiles of température, salinity, density and velocity. Physical data
recording started on January 27, 1995, and stopped on different days. In this
study we only consider the time interval in which ail the océanographie instrumentation was working on the whole mooring line, i.e. the first 240 days after
the moment of deployment, in order to get a complété hydrological and dynamic setting. Time sériés data analysis and interprétation are discussed in detail in
another work [16].
2.3 Sample Processing and Analytical Techniques
The material collected in each cup was first examined by both light and scanning électron microscopy (a detailed description of microscopie observations is
given in [17]), and then divided into a sériés of identical and homogeneous wet
subsamples for the détermination of total mass, biogenic silica, organic and
inorganic carbon. Sample preliminary treatment was performed according to
Heussner et al. [18]. The total mass was obtained by averaging the dry weight of
two to four aliquots taken from different subsamples of the original sample.
Particulate total (PTC) and organic carbon (POC) were determined by using a
LECO CS 125 carbon analyser; for POC détermination filters were previously
treated with 2N H,PO4 and IN HCl and concentrations were doubled to obtain
organic matter [19]. Particulate inorganic carbon (PIC) was calculated by différence (PIC = PTC - POC) and PIC values multiplied by a factor of 8.33 to estimate carbonate concentration, assuming that ail inorganic carbon is in the form
of calcium carbonate [20]. Détermination of biogenic silica was performed by a
time-series dissolution experiment in a 0.5 M NaOH solution at 85 °C for 5 h.
An aliquot of each sample was taken for analysis after every hour and the relative weight percent silica data were extrapolated back to time zéro to correct for
the silica eventually originating from coexisting clay minerais [21], The lithogenic fraction was calculated by subtracting the concentrations of organic matter, biogenic silica and carbonate from total dry weight [20].
A. Accornero et al.
min. Physical parameters were monitored by means of two Aanderaa RCM7
current meters with thermistor and conductive cells placed at 244- and 390-m
depth, two SBE Seacats with température and conductivity recorders positioned at 243 and 398 m, and one Aanderaa RCM7 current meter with only a
thermistor sensor located 20 m above the sea floor. An RDI ADCP current
meter profiler was fixed at the top of the mooring array to measure the upper
layer velocity, but it did not work, due to battery power failure.
2.2 Océanographie Time Sériés Data Analysis
Time sériés of currents, température and salinity measurements, acquired
every 30 min, were filtered and averaged. The averages were computed on several time intervals (1, 5, 10, 15 and 30 days) to highlight the behaviour of the
considered variables on different time scales. Vertical objective analysis [15]
was performed with the aim of reconstructing the temporal évolution of the
vertical profiles of température, salinity, density and velocity. Physical data
recording started on January 27, 1995, and stopped on different days. In this
study we only consider the time interval in which ail the océanographie instrumentation was working on the whole mooring line, i.e. the first 240 days after
the moment of deployment, in order to get a complété hydrological and dynamic setting. Time sériés data analysis and interprétation are discussed in detail in
another work [16].
2.3 Sample Processing and Analytical Techniques
The material collected in each cup was first examined by both light and scanning électron microscopy (a detailed description of microscopie observations is
given in [17]), and then divided into a sériés of identical and homogeneous wet
subsamples for the détermination of total mass, biogenic silica, organic and
inorganic carbon. Sample preliminary treatment was performed according to
Heussner et al. [18]. The total mass was obtained by averaging the dry weight of
two to four aliquots taken from different subsamples of the original sample.
Particulate total (PTC) and organic carbon (POC) were determined by using a
LECO CS 125 carbon analyser; for POC détermination filters were previously
treated with 2N H,PO4 and IN HCl and concentrations were doubled to obtain
organic matter [19]. Particulate inorganic carbon (PIC) was calculated by différence (PIC = PTC - POC) and PIC values multiplied by a factor of 8.33 to estimate carbonate concentration, assuming that ail inorganic carbon is in the form
of calcium carbonate [20]. Détermination of biogenic silica was performed by a
time-series dissolution experiment in a 0.5 M NaOH solution at 85 °C for 5 h.
An aliquot of each sample was taken for analysis after every hour and the relative weight percent silica data were extrapolated back to time zéro to correct for
the silica eventually originating from coexisting clay minerais [21], The lithogenic fraction was calculated by subtracting the concentrations of organic matter, biogenic silica and carbonate from total dry weight [20].