BODIPY 505/515, a lipophilic bright green fluorescent dye was tested for lipid detection in the microalga Tetraselmis subcordiformis. A concentration of 0.28 mu g ml(-1) and staining for 6 min was optimal. Lipid bodies stained with BODIPY505/515 had a characteristic green fluorescence. Their volumes were determined using the sphere volume formula. Lipid accumulation under different nitrogen concentrations was analyzed. With an increase in NaNO3 concentration from 0 to 240 mg L-1, the maximum algal concentration increased from 8.23 +/- 0.62 (x 10(5) cells ml(-1)) to 1.61 +/- 0.13 (x 10(6) cells ml(-1)), while the maximum volume of intracellular neutral lipid decreased from 9.78 +/- 1.77 mu m(3) cell(-1) to 6.00 +/- 0.59 mu m(3) cell(-1). A comparison of the lipid contents measured by BODIPY 505/515 staining and the gravimetric method showed a positive correlation coefficient of R-2 = 0.93. BODIPY 505/515 staining is a promising method in lipid quantitation in T. subcordiformis. (c) 2012 Elsevier Ltd. All rights reserved.