Dataset: Chlorophyll a - Eastern Tropical Pacific
Deployment: SJ07

A CTD-rosette was deployed between the surface (2 m) and a pre-determined depth.  The CTD was lowered at a rate of 30 m/min for the first 100 m and thereafter at 60 m/min. On the downcast, the depths of the fluorescence maxima, top of the thermocline, base of the thermocline, and other features of interest were noted on the CTD log sheet. Niskin bottles were fired at these depths and other pre-determined depths on the upcast to collect samples for chlorophyll analysis.  Chlorophyll samples were collected in 2 L amber bottles using tygon tubing without mesh for depths between surface and 2,700 m. Gloves were worn for sample collection and bottles and caps were rinsed three times before sample collection. The sample bottles were immediately processed after collection. The collection bottle was gently swirled and 200 to 2,148 mL were filtered under low vacuum onto a 25 mm GF/F filter. Filters were immediately placed in 13 mm borosilicate test tubes containing 7 mL 90% v/v HPLC grade acetone and extracted in the dark for 24 h at _-20 degrees C. After extraction, fluorescence was measured with a Turner Designs 10 AU fluorometer before and after acidification. The fluorometer was calibrated at sea using Chlorophyll a standards (Turner Designs). Chlorophyll a was determined using the methods of Parsons et al. (1984).

Reference: Parsons, T.R., Maita,Y., Lalli, C.M., 1984. A Manual of Chemical and Biological  Methods for Seawater Analysis. Pergamon Press, New York, pp. 107–110.