As part of the USJGOFS EqPac process study beam c profiles were obtained during two time-series occupations of the equator at 140°W (TT008 and TT012). The beam attenuation profiles clearly show a diel cycle, with morning lows and evening highs. Transforming the beam c data into suspended particle concentration, and then integrating the particle load to the 1% and 0.1% light depths for each day yields the diel change in the particle load. The estimate of the net daily particulate organic carbon increase to the 1% light level averaged over the TT008 cruise was 26 mmol C m - 2 day - 1 , and 41 mmol m - 2 day - 1 for TT012. The integration of the 0.1% light level was 29 mmol m - 2 day - 1 during TT008, and 41 mmol m - 2 day - 1 for TT012. The difference between the optical estimates of the change in the particle pool and primary production estimates can be ascribed to removal processes in situ, primarily grazing and aggregation.