Automated estimation of chlorophyll pigments by fluorescence

This method derives from a report C. J. Lorenzen Deep-Sea Res., 13 223, 1966) with some further work reported by one of us (Strickland, Deep-Sea Res., In Press). Sea water is pumped toough a cuvette in a specially sensitive Turner fluorometer and the fluorescence of the living plankton cells measured directly. The method is an invaluable semiquantitative tool for measuring the surface concentration of phytoplankton in a ship underway but requires very frequent standardization if it is to be used as a precise technique in eutrophic waters. No generally applicable precision can be quoted. The method will measure between about OjOS and 20 mg chlorophyll a/nP. Greater quantities (such as found in red-tide blooms) can be handled if a specially constructed door 1 is made with a very small hole. 

A Turner fluorometer, Model HI with a flow-through door and cuvette (f-inch orifices). Use a high intensity F4T.5. blue lamp with a blue Coming filter CS.5-60 for the excitation light and a red Coming filter CS.2-64 for the emitted light. The standard photomultiplier must be replaced Ity a red sensitive one (R136). 

Sea water or distilled water should be drawn through the cuvette using a small pump and a three-way tap. Depending on the source of the sample some form of debubbling device will generally be needed see Section IV.13,C). 

A 10-mv recorder for the ouQ)ut of the fluorometer with the outyut adjusted as described in the Turner instmment manual is required. 

Draw distilled water through the cuvette until it has been thoroughly flushed and filled. Turn off the pump to conserve water and adjust the zero with door 1 so that the blank is near zero. Switch successively to doors 3, 10, and 30 record blanks for each door. Repeat this operation once or twice a day. 

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