Dataset: LB_2012_Ship_Chl

At selected stations and depths, Niskin water samples were collected using the ship’s CTD/carousel water sampler (Sea-Bird SBE 25 Sealogger CTD; Sea-Bird SBE 32C carousel pylon; 8-L Ocean Test Equipment Model 110 external-closure water sampling bottles).  Samples were transferred to 2 L polycarbonate bottles from the Niskin bottles via Tycon tubing and processed in the ship’s wet lab.  Triplicate samples (250 mL) were filtered onto GF/F glass fiber filters.  The filters were folded and inserted into screw-capped cyrovials labelled with a cyropen (date, station, depth, volume filtered, replicate number), then frozen in liquid nitrogen.  Sample information was recorded on a sample log sheet that was scanned for an electronic pdf record after each cruise.  

Samples were stored in liquid nitrogen until analyzed at the shore laboratory.  Analysis was by the fluorometric method, based on JGOFS protocols (1996).  Frozen filters were placed in a polyethylene tube to which 10 mL 90% acetone was added for extraction.  After several hours extraction in the freezer, the filters were disrupted using a probe-type sonicator, with care to keep samples cold and in dim light.  Filter debris was cleared by centrifugation and the cleared extracts were decanted into cylindrical glass cuvettes and read in a Turner Designs Model 10AU fluorometer, with readings recorded before and after addition of one drop 2 N HCl.  Chlorophyll and phaeopigment concentrations were calculated as described in the JGOFS protocols (1996).  The fluorometer scale factor (calibration factor) was determined using a chlorophyll reference solution (90% acetone extract of a filtered diatom culture) with the reference concentration determined spectrophotometrically (extinction at 664 nm) using a Cary Model 3 spectrophotometer.  The stability of the laboratory fluorometer over time was tracked by periodic measurements of a stable fluorescence reference solution (Basic Blue 3 in Milli-Q water).