Timothy R. Parsons 
Manual of Chemical & Biological Methods for Seawater Analysis [PDF ebook] 

An introduction to the quantitative analysis of seawater, describing in detail biological and chemical techniques, which are considered to be amongst those most often used by biological oceanographers. The manual provides complete instructions for the addition of reagents and calculation of results with reference material for each method so that the original texts can be consulted if necessary. In general, the techniques require a minimum of prior professional training and methods needing very expensive equipment have been avoided.