Sampling sinking particulates

Below about 200 m, PON concentrations tend to asymptote to similar levels of about 0.1 to 0.3 pmol kg", irrespective of the large differences in PON in the euphotic zone. Overall, PON dynamics in the aphotic zone tends to follow that of particulate organic carbon (POC), with a stoichiometric C N ratio of about 7.1 0.1 (equivalent to 16 114 2) for the particles sinking out of the euphotic zone (Schneider et al, 2003) (see also Hebei and Karl (2001) for long-term observations of the POC and PON dynamics in an oligotrophic environment). In their analysis of sediment trap samples and particles collected by in situ pumps, Schneider et al (2003) also noticed a slight increase of this ratio with depth of about 0.2 per 1000 m, so that particles sinking across 1000 m have a C N ratio very close to the 117 16 ratio proposed by Anderson and Sarmiento (1994). 

Figure 14 Fluxes and composition of particulate organic carbon in the equatorial Pacific Ocean, (a) POC fluxes (mgm d ). (b) Corresponding fractions of amino acid, carbohydrate, lipid, and molecularly uncharacterized carbon (biochemical class-carbon as a percentage of total OC) in plankton, sediment traps (105 m, l,000m, >3,500 m) and surface sediment samples. The fraction of molecularly uncharacterized organic carbon (calculated as the difference between total OC and the sum of amino acid - - carbohydrate - - Upid) increases with more extensive degradation to become the major constituent in deeper POC samples (after Wakeham et al., 1997). (c) Calculated weight percentages of amino acid, carbohydrate, and lipid in plankton and in sinking (sediment trap) particles in the upper and lower water column as determined by solid-state C-NMR spectroscopy (source Hedges et al., 2001).

Particulate Calcium in WCR 82-B. Calcium is a major component of particulate matter and occurs largely as calcite (5). Most particulate Ca is small and is predominantly present in 10-20-jLtm sized coccolithophores in surface waters and in 1-5- im sized coccoliths below the euphotic zone (5). Individual coccoliths sink only fractions of a meter per day (2, 5). Hence, the <53-fim Ca concentration in waters below 100 m would be expected to show the least temporal variability of all particulate elements sampled. For this reason, Ca data from below 100 m was used for comparison of samples collected with GF and MQ filters and by the LVFS and MULVFS. 

Figure 9 shows vertical G profiles for DIG and DOM as well as " G results for selected samples of sinking and suspended particulate organic matter (POM), HMW DOM, and monosaccharides isolated from selected depths at a station in the North-east Pacific Ocean. Individual monosaccharides were obtained by hydrolysis of HMW DOM, and purified and... 

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