||P.225 right column 4th paragraph: "In the euphotic layer, mixotrophs could also efficiently compete with heterotrophs, as has been observed in fresh water (ref 13). In the temperate North Atlantic the high abundance of bacterioplankton sustained a sizeable population of aplastidic protists (0.51 ± 0.37 ×10^3 cells/ml, mean ± standard deviation of 13 measurements), which showed more efficient cell predation than plastidic protists (Fig. 1a). Although the average abundance of aplastidic protists was only 6% of the sum of the abundance of plastidic protists, the former were responsible for up to 60% of the bacterivory, supporting the view that specialization pays dividends. However, if the ecological success of a population is measured not by its efficiency but by its abundance (Fig. 1b), then mixotrophic plastidic protists control planktonic microbial communities of surface waters in the temperate open ocean and probably in the tropical waters as well (Fig. 1c)."