Concentrations of lipid phosphorus and its abundance in dissolved and particulate organic phosphorus in coastal seawater

Analytical procedures to determine lipid phosphorus (lipid P) in seawater were developed and tested using a combination of solvent and solid-phase extraction. Lipid P was extracted from particulate and dissolved matter in seawater with a solvent mixture of chloroform and methanol. Silica gel solid-phase extraction (SPE) was evaluated using phospholipid and hydrophilic compounds. SPE exhibited high recoveries of phospholipids from the solvent mixture and was also effective in removing contamination from hydrophilic compounds. The method was applied to coastal seawater samples to investigate the quantitative significance of lipid P in marine organic P. In samples collected from Tokyo Bay, Japan, and Corpus Christi Bay, USA, concentrations of particulate lipid P ranged from 31 to 300 nM, which corresponded to 3–14% of the total particulate P. Concentrations of dissolved lipid P were low ranging from 0.7 to 6 nM, which were less than 1% of the total dissolved organic P concentrations. Thus, lipid P is a significant component of particulate P, but a rather minor component of dissolved organic P.