Elemental composition of individual pico- and nano-sized marine detrital particles in the northwestern Mediterranean Sea

The elemental composition of individual < 10 mu m detrital particles from Mediterranean surface waters was analysed using a Transmission Electron Microscope (TEM) equipped with an energy dispersive X-Ray microanalyser. Results show that carbon and phosphorus content per detritus volume are much higher in pico-detrital particles < 2 mu m (42 kg C m(-3) and 1 kg P m(-3)) than in 5-10 mu m detrital particles (20 kg C m-3 and 0.1 kg P m(-3)). The C:N:P atomic ratios for different sized fractions of the detrital particles were found to be 82:10:1 for < 2 mu m particles, 120:29:1 for 2-5 mu m particles and 308:37:1 for 5-10 mu m particles. The average ratio for all size classes of detrital particles (< 10 mu m) was 132:23:1. The differences in elementary compositions of the detrital particles studied here suggest that the different size fractions probably have different origins. The role and origins of < 10 mu m detrital particles within the biogeochemical cycles are discussed.